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  • Polymer and Materials Science  (94,637)
  • Organic Chemistry  (68,947)
  • 1
    Keywords: Life sciences ; Biotechnology ; Organic Chemistry ; Biochemistry ; Cell Biology ; Life sciences ; Cell Biology ; Biochemistry, general ; Biotechnology ; Organic Chemistry ; Springer eBooks
    Description / Table of Contents: 1. Trends in bioprobe research -- 2. Cell proliferation and differentiation -- 3. Epigenetics -- 4. Apoptosis and autophagy -- 5. Adaptive and innate immune Systems -- 6. Bioprobes at a glance
    Abstract: This new edition provides the most advanced research using bioprobes on the chemical control of 1) cell cycle and differentiation, 2) epigenetics, 3) apoptosis and autophagy, and 4) immune response. The “bioprobe”, first proposed in the first edition, has become an indispensable tool for chemical biology and has substantially assisted in the investigation of complex biochemical processes of cells. New areas of investigation such as stem cell research, epigenetic research, and autophagy research have rapidly advanced in the past 10 years. Including these new findings, this second edition supplies up-to-date information on the biochemical tools called bioprobes. Data on each bioprobe, such as chemical structure, origin, function, and references, are presented as one item in this volume. Readers will easily find useful information and will be able to determine the appropriate bioprobes to investigate cell functions. The information on bioprobes and their use in research makes this book a valuable source for researchers in diverse fields. Not only scientists in academia but also in the pharmaceutical industries will discover the most important information about small molecules useful for drug discovery
    Pages: VIII, 384 p. 173 illus., 10 illus. in color. : online resource.
    Edition: 2nd ed. 2017.
    ISBN: 9784431565291
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  • 2
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    Cham : Springer International Publishing
    Keywords: Life sciences ; Medicine ; Chemistry, Organic ; Biochemistry ; Life sciences ; Protein Science ; Biomedicine general ; Organic Chemistry ; Springer eBooks
    Description / Table of Contents: Sequences -- Structures -- Systems
    Abstract: This book describes more than 60 web-accessible computational tools for protein analysis and is totally practical, with detailed explanations on how to use these tools and interpret their results and minimal mentions to their theoretical basis (only when that is required for making a better use of them). It covers a wide range of tools for dealing with different aspects of proteins, from their sequences, to their three-dimensional structures, and the biological networks they are immersed in. The selection of tools is based on the experience of the authors that lead a protein bioinformatics facility in a large research centre, with the additional constraint that the tools should be accessible through standard web browsers without requiring the local installation of specific software, command-line tools, etc. The web tools covered include those aimed to retrieve protein information, look for similar proteins, generate pair-wise and multiple sequence alignments of protein sequences, work with protein domains and motifs, study the phylogeny of a family of proteins, retrieve, manipulate and visualize protein three-dimensional structures, predict protein structural features as well as whole three-dimensional structures, extract biological information from protein structures, summarize large protein sets, study protein interaction and metabolic networks, etc. The book is associated to a dynamic web site that will reflect changes in the web addresses of the tools, updates of these, etc. It also contains QR codes that can be scanned with any device to direct its browser to the tool web site. This monograph will be most valuable for researchers in experimental labs without specific knowledge on bioinformatics or computing
    Pages: VIII, 106 p. 40 illus. in color. : online resource.
    ISBN: 9783319127279
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  • 3
    Keywords: Medicine ; Neurochemistry ; Organic Chemistry ; Radiology ; Biomedicine ; Neurochemistry ; Organic Chemistry ; Imaging / Radiology ; Springer eBooks
    Abstract: This book explores the revolutionary fMRI field from basic principles to state-of-the-art research. It covers a broad spectrum of topics, including the history of fMRI's development using endogenous MR blood contrast, neurovascular coupling, pulse sequences for fMRI, quantitative fMRI, genetic imaging using fMRI, multimodal neuroimaging, brain bioenergetics and function, and molecular-level fMRI. Comprehensive and intuitively structured, this book examines the physiological basis of fMRI, the basic principles of fMRI and its applications, and the latest advances of the technology. The final chapter discusses the field's future. fMRI: From Nuclear Spins to Brain Function is an ideal resource for clinicians and researchers in the fields of neuroscience, psychology, and MRI physics. This book also: ℗ʺ℗ ℗ ℗ ℗ ℗ ℗ ℗ ℗ Explores a wide range of topics, covering the physical basics, physiological bases, a selection of various applications, and cutting-edge advances in fMRI ℗ʺ℗ ℗ ℗ ℗ ℗ ℗ ℗ ℗ Engages the reader with a first-person account of the development and history of the fMRI field by the authors ℗ʺ℗ ℗ ℗ ℗ ℗ ℗ ℗ ℗ Discusses fMRI applications in a variety of contexts, including fMRI of the visual system, auditory cortex, and sensorimotor system as well as the history of fMRI's development using endogenous MR blood contrast, neurovascular coupling, pulse sequences for fMRI, and℗ quantitative fMRI ℗
    Pages: XVIII, 929 p. 235 illus., 179 illus. in color. : online resource.
    Edition: 1st ed. 2015.
    ISBN: 9781489975911
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  • 4
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    Cham : Springer International Publishing
    Keywords: Medicine ; Chemistry, Organic ; Life sciences ; Biomedicine ; Biomedicine general ; Life Sciences, general ; Organic Chemistry ; Springer eBooks
    Description / Table of Contents: Alkanes, Composition, Constitution and Configuration -- Functional Groups -- Electronic Structure of Organic Molecules -- Alkenes and Alkynes -- Substitutions on Saturated Carbon Atom -- Nucleophilic Additions -- Stereochemistry, Symmetry and Molecular Chirality -- Derivatives of Carboxylic Acids -- Electrophilic Substitutions -- Cycloadditions -- Organic Natural Products
    Abstract: This work provides an overview of the basics of organic chemistry for non-chemists. As such, this book should be very useful for university students of biology, molecular biology, ecology, medicine, agriculture, forestry, and other specialties where the knowledge of organic chemistry plays the important role but is not a core discipline. The book should also be of interest to non-professionals, and it may serve as a manual or repetitorium to high school teachers. ℗ The text is divided into eleven chapters on the basis of the systematization of fundamental organic reaction types, and classes of organic compounds. The first chapters comprise fundamental aspects of structural theory, reaction mechanisms, electronic structure, some basic spectroscopy, and properties of main groups of organic compounds. At the end of the book, the largest chapter contains the elements of the organic chemistry of natural products. Comparison of the reactions in the laboratory with the analogous molecular transformations in living cells will enable the reader to better understand the basic principles of biochemistry
    Pages: XIII, 179 p. 331 illus., 51 illus. in color. : online resource.
    ISBN: 9783319076058
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  • 5
    Keywords: Medicine ; Spectroscopy ; Biotechnology ; Chemistry, Organic ; Chemistry, Physical organic ; Biochemistry ; Biomedicine ; Biomedicine general ; Spectroscopy/Spectrometry ; Biotechnology ; Physical Chemistry ; Organic Chemistry ; Biochemistry, general ; Springer eBooks
    Description / Table of Contents: The basis of Nuclear Magnetic Resonance Spectroscopy -- Spectroscopic parameters in Nuclear Magnetic Resonance -- Basic NMR experiments -- Biomolecular NMR
    Abstract: This book intends to be an easy and concise introduction to the field of nuclear magnetic resonance or NMR, which has revolutionized life sciences in the last twenty years. A significant part of the progress observed in scientific areas like Chemistry, Biology or Medicine can be ascribed to the development experienced by NMR in recent times. Many of the books currently available on NMR deal with the theoretical basis and some of its main applications, but they generally demand a strong background in Physics and Mathematics for a full understanding. This book is aimed to a wide scientific audience, trying to introduce NMR by making all possible effort to remove, without losing any formality and rigor, most of the theoretical jargon that is present in other NMR books. Furthermore, illustrations are provided that show all the basic concepts using a naive vector formalism, or using a simplified approach to the particular NMR-technique described. The intention has been to show simply the foundations and main concepts of NMR, rather than seeking thorough mathematical expressions
    Pages: XII, 115 p. 36 ill. : digital.
    ISBN: 9789400769762
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  • 6
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    Dordrecht : Springer
    Keywords: Medicine ; Spectroscopy ; Chemistry, Organic ; Chemistry, Physical organic ; Chemistry ; Biomedicine ; Biomedicine general ; Organic Chemistry ; Physical Chemistry ; Spectroscopy/Spectrometry ; Organometallic chemistry ; Electrochemistry ; Springer eBooks
    Description / Table of Contents: Molecular structures -- An overview of synthetic methods for preparation of nitrosoaromatic compounds -- Molecular properties and spectroscopy -- Organometallic compounds -- Bilological systems
    Abstract: This volume will present the reader with an update on the scientific research on organic chemistry of nitroso compounds that was performed in the last two decades. The overview will include the original synthetic applications of nitroso compounds, but will also cover the discovery of novel physico-chemical phenomena and their potential future uses. The properties that form the basis for this technological potential originate from the intriguing property of C-nitroso molecules to form dimers through the formation of a relatively weak nitrogen-nitrogen double bond. The equilibrium between the different monomeric and dimeric forms, which appears under controlled environmental parameters, opened new areas of research in organic chemistry.The novel paradigm presented in this volume includes insight into the original problem of organic reactivity and synthesis, but also sheds light on the solid-state reaction mechanisms. A number of fascinating photochemical, electrochemical, supramolecular, and biological properties, as well as advanced techniques in spectroscopy, now enables us to use these compounds as molecular models for studying a number of general chemical concepts.℗
    Pages: : digital.
    ISBN: 9789400763371
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  • 7
    Keywords: Life sciences ; Toxicology ; Chemistry, Organic ; Pharmacy ; Oceanography ; Biochemistry ; Aquatic biology ; Life sciences ; Biochemistry, general ; Organic Chemistry ; Freshwater & Marine Ecology ; Oceanography ; Pharmacology/Toxicology ; Pharmacy ; Springer eBooks
    ISBN: 9789048138340
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  • 8
    Keywords: Life sciences ; Chemistry, Organic ; Carbohydrates ; Biochemistry ; Proteomics ; Cytology ; Cell Membranes ; Life sciences ; Biochemistry, general ; Organic Chemistry ; Carbohydrate Chemistry ; Cell Biology ; Membrane Biology ; Proteomics ; Springer eBooks
    Pages: : digital.
    ISBN: 9781461433811
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  • 9
    Keywords: Chemistry ; Chemistry, Organic ; Chemistry ; Organic Chemistry ; Springer eBooks
    Pages: : digital
    ISBN: 9781441972705
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  • 10
    Keywords: Life sciences ; Chemistry, Organic ; Nucleic Acids ; Biochemistry ; Life sciences ; Nucleic Acid Chemistry ; Protein Science ; Organic Chemistry ; Springer eBooks
    Pages: : digital
    ISBN: 9783642169311
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  • 11
    Keywords: Medicine ; Toxicology ; Pharmaceutical technology ; Chemistry, Organic ; Chemical engineering ; Biochemistry ; Biomedicine ; Pharmacology/Toxicology ; Pharmaceutical Sciences/Technology ; Organic Chemistry ; Medicinal Chemistry ; Medical Biochemistry ; Industrial Chemistry/Chemical Engineering ; Springer eBooks
    Pages: : digital
    ISBN: 9783034801256
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  • 12
    ISSN: 0887-624X
    Keywords: (1→6)-2,5-anhydro-D-glucitol ; HPLC ; optical resolution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cyclopolymerization of 3,4-di-O-allyl-1,2 : 5,6-dianhydro-D-mannitol (1) was carried out using BF3·OEt2 and t-BuOK. The polymer obtained by the polymerization with BF3·OEt2 mainly consisted of (1→6)-bonded 3,4-di-O-allyl-2,5-anhydro-D-glucitol as the five-membered constitutional repeating unit, though it contained a small amount of other cyclic repeating units. On the other hand, during the polymerization using t-BuOK, the stereoregular polymer (1→6)-linked 3,4-di-O-allyl-2,5-anhydro-D-glucitol (2) was synthesized via a regio- and stereoselective mechanism. Cleavage of the allyl ether linkage in polymer 2 occurred to produce the polymer consisting of only 2,5-anhydro-D-glucitol units, i.e., (1→6)-2,5-anhydro-D-glucitol (3). Chromatographic enantioseparation of chloroquine and tröger base has been performed on (3,5-dimethylphenyl)carbamate and 4-methylbenzoate derivatives of 3 as a chiral stationary phase for high-performance liquid chromatography. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 901-909, 1998
    Additional Material: 4 Ill.
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  • 13
    ISSN: 0887-624X
    Keywords: temperature sensitive ; particle ; emulsion polymerization ; morphology ; adsorption ; enzyme ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two kinds of temperature-sensitive composite polymer particles were prepared by seeded emulsion copolymerizations of (dimethylamino)ethyl methacrylate and ethylene glycol dimethacrylate with 0.14 μm-sized polystyrene and 0.26 μm-sized poly(methylmethacrylate) seed particles. To evaluate the usefulness as a carrier for biomolecules, the enzymatic activities of trypsin adsorbed on these two composite polymer particles were measured at temperatures above and below each lower critical solution temperature (LCST). In both cases, adsorbed trypsin retained its enzymatic activity during repeated adsorption/desorption measurements. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 883-888, 1998
    Additional Material: 7 Ill.
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  • 14
    ISSN: 0887-624X
    Keywords: AMGLU ; A6BMG ; A6TMG ; ring-opening polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three new 1,4-anhydro-glucopyranose derivatives having different hydroxyl protective groups such as 1,4-anhydro-2,3,6-tri-O-methyl-α-D-glucopyranose (AMGLU), 1,4-anhydro-6-O-benzyl-2,3-di-O-methyl-α-D-glucopyranose (A6BMG), and 1,4-anhydro-2,3-di-O-methyl-6-O-trityl-α-D-glucopyranose (A6TMG) were synthesized from methyl α-D-glucopyranoside in good yields. Their polymerizability was compared with that of 1,4-anhydro-2,3,6-tri-O-benzyl-α-D-glucopyranose (ABGLU) reported previously. The trimethylated monomer, AMGLU, was polymerized by a PF5 catalyst to give 1,5-α-furanosidic polymer having number-average molecular weights (M̄n) in the range of 2.8 × 103 to 6.8 × 103. The 13C-NMR spectrum was compared with that of methylated amylose and cellulose. Other anhydro monomers, A6BMG and A6TMG, gave the corresponding 1,5-α furanosidic polymers having M̄n = 17.1 × 103 and 1.8 × 103, respectively. Thus, the substituents at the C2 and C6 positions were found to play an important role for the ring-opening polymerizability of the 1,4-anhydro-glucose monomers. In addition, debenzylation of the tribenzylated polymer gave free (1 → 5)-α-D-glucofuranan. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 841-850, 1998
    Additional Material: 6 Ill.
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  • 15
    ISSN: 0887-624X
    Keywords: free volume ; autoacceleration ; inhibition ; tertiary amines ; friction coefficient ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The epoxy-diamine cure process was studied. We found that the mechanism can be described in three steps: (i) initiation up to 20-25% of conversion. (ii) autoacceleration and (iii) inhibition. It has been observed that after the initiation there is a clear autoacceleration effect which has been explained in terms of free volume, considerations: the volume occupied by the products of reaction diminishes the available volume increasing the “local concentration” of the reactants and therefore the rate of reaction. The reaction was followed by FTIR (near infrared) as the main technique. We used a purified epoxy resin as well as phenyl glycidyl ether cured with m-xylenediamine. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1001-1016, 1998
    Additional Material: 11 Ill.
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  • 16
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper discusses the poly(ethylene-co-p-methylstyrene) copolymers prepared by metallocene catalysts, such as Et(Ind)2ZrCl2 and [C5Me4(SiMe2NtBu)]-TiCl2, with constrained ligand geometry. The copolymerization reaction was examined by comonomer reactivity (reactivity ratio and comonomer conversion versus time), copolymer microstructure (DSC and 13C-NMR analyses) and the comparisons between p-methylstyrene and other styrene-derivatives (styrene, o-methylstyrene and m-methylstyrene). The combined experimental results clearly show that p-methylstyrene performs distinctively better than styrene and its derivatives, due to the cationic coordination mechanism and spatially opened catalytic site in metallocene catalysts with constrained ligand geometry. A broad composition range of random poly(ethylene-co-p-methylstyrene)copolymers were prepared with narrow molecular weight and composition distributions. With the increase of p-methylstyrene concentration, poly(ethylene-co-p-ethylstyrene)copolymer shows systematical decrease of melting point and crystallinity and increase of glass transition temperature. At above 10 mol % of p-methylstyrene, the crystallinity of copolymer almost completely disappears. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1017-1029, 1998
    Additional Material: 8 Ill.
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  • 17
    ISSN: 0887-624X
    Keywords: electroconductive polymer ; polyimide-carbon black composite ; direct polycondensation ; salt monomer method ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 3 Ill.
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  • 18
    ISSN: 0887-624X
    Keywords: acid-catalyzed deprotection mechanism ; chemically amplified resist ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mechanism of acid-catalyzed deprotection of poly(4-tert-butyloxycarbonyloxy-styrene), PBOCST, in chemically amplified resists has been elucidated in terms of elementary processes by means of semiempirical molecular orbital calculations. It is concluded that the overall deprotection of tert-butyloxycarbonyl (t-BOC) group proceeds stepwise; i.e., (a) the first products are an acid carbonate and a tert-butyl cation; (b) a phenolic compound is the secondary and final product from the acid carbonate, which is realized by assistance with a counter anion accompanied by acid; (c) the counter anion also assists acid regeneration from the tert-butyl cation to produce isobutylene. The yield rate of the phenol is proportional to the product of concentrations of the polymer, the catalytic acid, and the counter anion. The activation energy (21 kcal/mol) calculated for the rate-determining step (a) is in good agreement with an experiment. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1035-1042, 1998
    Additional Material: 10 Ill.
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  • 19
    ISSN: 0887-624X
    Keywords: poly(lactide) ; hydrolysis ; degradation ; erosion ; alkaline solution ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrolysis of poly(L-lactide) (PLLA) films in 0.01N NaOH at 37°C was investigated by gel permeation chromatography, differential scanning calorimetry, scanning electron microscopy, and polarizing optical microscopy. The change in molecular weight distribution and surface morphology of PLLA films during hydrolysis revealed that PLLA film hydrolysis in dilute alkaline solution proceeded mainly via the surface erosion mechanism. An insignificant dependence of the rate of weight loss per unit surface area on the PLLA film thickness also supported this conclusion. Etching of the outside of PLLA spherulites resulted in preferred hydrolysis of PLLA chains in the amorphous region. The disorientation of lamella and inhomogeneous erosion in the spherulites implied that hydrolysis of PLLA chains occurred predominantly in the amorphous region between the crystalline regions in the spherulites. The rate of weight loss per unit surface area decreased linearly with the increase in the initial crystallinity of PLLA film, while the radius of spherulites had practically no significant effect on the hydrolysis of PLLA film. The specific low molecular weight of PLLA chains produced by hydrolysis increased with the rise in annealing temperature of the PLLA film, suggesting that the PLLA chains released were the component of one fold in the crystalline region. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 59-66, 1998
    Additional Material: 8 Ill.
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  • 20
    ISSN: 0887-624X
    Keywords: one-pot oxidation polymerization ; dithiol ; bifunctional five-membered cyclic dithiocarbonates ; diamine ; polydisulfide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: One-pot oxidation polymerization of dithiols, obtained from bifunctional five-membered cyclic dithiocarbonates (4a and 4b) with two equivalents of amines, was studied. The monomers 4a and 4b were synthesized by the reactions of bisphenol A diglycidyl ether and neopentyl glycol diglycidyl ether with carbon disulfide, respectively. Polydisulfides with M̄ns 4600-20,200 were obtained quantitatively in the oxidation polymerization of the dithiols obtained in situ by the reactions of 4a with benzylamine, n-butylamine, and piperidine. On the other hand, dithiols obtained from 4b with benzylamine, afforded cyclic disulfides as well as the polydisulfide under similar conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 79-84, 1998
    Additional Material: 2 Ill.
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  • 21
    ISSN: 0887-624X
    Keywords: multiarm-star ; polyisobutylene ; living polymerization ; macroinitiator ; 4-(1-hydroxy-1-methylethyl)styrene-co-styrene ; Core first method ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article describes the synthesis of high molecular weight multiarm-star branched polyisobutylenes by living polymerization, using multifunctional initiators, and their initial characterization. First, macrointiators carrying tert-hydroxy function-alities were synthesized by the radical copolymerization of 4-(1-hydroxy-1-methylethyl)-styrene with styrene. This copolymerization system was found to be ideal with r1 ≡ r2 ≡ 1. Selected macroinitiators with average functionalities of 8-73 were then used to synthesize the star-branched polyisobutylenes. Polymers with molecular weights up to M̄n = 400,000 were obtained within 30-60-min reaction times, while under similar conditions the monofunctional 2-chloro-2,4,4-trimethylpentane initiator yielded M̄n ≈ 10,000 in 20 min. This can be viewed as an indirect proof that simultaneous multiple initiation took place with the macroinitiators. Under controlled conditions a branchedpolyisobutylene with M̄n = 375,000 and MWD = 1.2, and theoretically calculated 23 arms, with no detectable side products was obtained under living conditions in 60 min; the molecular weight of this polymer increased linearly with time. The branched structure of the polymers were demonstrated by SEC-LLS analysis and core destruction of selected samples. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 85-92, 1998
    Additional Material: 9 Ill.
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  • 22
    ISSN: 0887-624X
    Keywords: stereoregular poly(ester amides) ; carbohydrate-based polymers ; polycondensation reactions ; chiral polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two poly(ester amides) containing three methoxy groups stereoregularly attached to the main chain have been prepared by using naturally occurring L-arabinose and D-xylose as the starting materials. The polymers were prepared by the active ester polycondensation method and characterized by elemental analysis, IR, and 1H- and 13C-NMR spectroscopies. Both viscosimetry and GPC were used to estimate the molecular weights. The polymers are hydrophilic, one of them being water soluble, and exhibited moderate optical activity. Thermal and X-ray diffraction studies revealed that they are slightly crystalline and stable up to 250°C under nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 67-77, 1998
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  • 23
    ISSN: 0887-624X
    Keywords: p-nitrophenylacetylene ; phenylacetylene ; copolymers ; structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copolymers of phenylacetylene (PA) and p-nitrophenylacetylene (pNPA) with various monomers ratios were prepared and characterized. The solubility of copolymers is dependent on the number of PA units in the chain. They show a good degree of stereoregularity and the MWs are in the 103-105 a.m.u. range, depending on the monomers and catalyst molar ratios. The soluble samples exhibit film-forming properties and the film-surface morphology may be varied by using different solvents. The copolymers give good electrical response to relative humidity variations. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 93-102, 1998
    Additional Material: 5 Ill.
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  • 24
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: oxetane ; polyether ; phase-transfer catalyst ; ring opening ; modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new oxetane-containing polyether was synthesized by polycondensation of bisphenol-AF (BPAF) with 3,3-bis(chloromethyl)oxetane (BCMO) using the phase-transfer catalyzed method. The polycondensation proceeded very smoothly in aromatic solvents, catalyzed by quaternary ammonium or phosphonium salts, such as tetrabutylammonium bromide (TBAB) and tetrabutylphosphonium bromide (TBPB), to afford the polymer with high yield and molecular weight. Further, a polymer with relatively high molecular weight was obtained when the reactions were carried out in aromatic and lipophilic solvents such as benzene and nitrobenzene. The modification of this oxetane-containing polyether was easily achieved by carrying out ring-opening of the oxetane ring by using hydrogen chloride in methylene chloride, which produced a functional polymer containing hydroxyl and chloro groups. The oxetane-containing polyether was observed to be soluble in chlorinated aliphatic hydrocarbons such as methylene chloride and chloroform, as well as polar solvents such as DMSO, DMF, and DMAc, and also some common organic solvents such as benzene and toluene. However, it was insoluble in both aliphatic hydrocarbons as well as alcoholic solvents. The oxetane-containing polyether was observed to start losing weight at around 300°C under nitrogen atmosphere, and 10% weight loss was measured to be 411°C. The glass transition temperature of the oxetane-containing polyether was measured to be 134°C and the wide-angle X-ray diffraction pattern revealed this polymer to be semicrystalline. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 103-107, 1998
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  • 25
    ISSN: 0887-624X
    Keywords: homogeneous Ti-based catalyst ; methylaluminoxane ; catalytic activity ; UV/visible spectroscopy ; syndiotactic polystyrene ; polymorphic structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The catalytic activities in syndiospecific polymerization of styrene in hydrocarbon using homogeneous Ti-based catalysts in the presence of methylaluminoxane (MAO) were investigated through UV/visible spectroscopic analysis. A strong UV absorption band of CpTiCl3, itself, incipiently appeared at λmax = 400 nm in toluene, followed by a bathochromic shift with its remarkable decrease by the addition of MAO. The absorption band intensity at λmax = 400 nm arising from delocalization of π-electrons on the cyclopentadienyl ring decreased by methylation in the presence of MAO with regard to the mechanism for production of an active center (“cation-like”), for example, the change of the ionic nature. The intensity decrease at λmax = 400 nm was suppressed over 2000 of the [Al]/[Ti] ratio. In the case of Ti(OC4H9)4 having a σ-ligand, new and broad UV absorption bands were developed at λmax = 340 nm and 410 nm in the presence of MAO in contrast with the CpTiCl3/MAO system. Comparison between the relative absorption intensities at λmax = 340 nm and 410 nm led to the determination of a maximum catalytic activity of Ti(OC4H9)4 in the presence of MAO related to the polymerization yield. The maximum polymerization yield was observed with regard to the relative maximum value of the absorption intensity at λmax = 410 nm with the [Al]/[Ti] ratio (500). From observation for polymorphism of the final products via differential scanning calorimetric analysis (DSC), the thermally unstable β-form seemed to be produced by the CpTiCl3/MAO system independent of the MAO concentration, the Ti(OC4H9)4/MAO system produced a thermally stable α-form in the low MAO concentration (up to 100 of the [Al]/[Ti] ratio), and a mixture of α- and/or β-forms over 200 of the [Al]/[Ti] ratio under our experimental conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1733-1741, 1998
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  • 26
    ISSN: 0887-624X
    Keywords: coupling reaction ; living polymer ; microstructure ; coupling yield ; 1,4-enchainment ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The most important variable affecting the yield in the coupling reactions of polymeric organolithium compounds with chlorosilane compounds has been investigated through size-exclusion chromatographic (SEC) analysis. The coupling reaction of poly(styryl)lithium with dichlorodimethylsilane as a silane-coupling agent provided 44 wt % of the coupling yield. The coupling yield, depending on the chain end reactivity of active polymers, was not greatly affected. The addition of a Lewis base such as N,N,N′,N′-tetramethylethylenediamine (TMEDA) even after complete polymerization of the dienes in hydrocarbon seems to affect the coupling reaction, resulting in decreasing the yield. The 1,2- or 3,4-enchain contents in the polydiene backbones affected the reduction of the linking efficiency in the coupling of the poly(dienyl)lithiums with chlorosilanes as the linking agent. The linking yields of the active polymers including over 75 mol % of 1,2- or 3,4-enchainment on the polydiene segment were below 20 wt %. The linking yields exhibited a dependence not only on the steric requirement of the chain end, but also the microstructure of the polydiene segment. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1743-1753, 1998
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  • 27
    ISSN: 0887-624X
    Keywords: 1-(trifluoromethyl)-2,3,5,6-benzenetetracarboxylic dianhydride ; amide acid ; poly(amic acid) ; isomeric unit ; nuclear magnetic resonance spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two different poly(amic acid)s were synthesized by the polycondensations of 1-(trifluoromethyl)-2,3,5,6-benzenetetracarboxylic dianhydride (CF3DAN) with p-phenylene diamine and benzidine. In addition, an amide acid model compound was prepared from CF3DAN and aniline. Isomeric units in the poly(amic acid)s as well as the amide acid were investigated by 1H and 13C-nuclear magnetic resonance (NMR) spectroscopies. Spectroscopic results indicate that the major isomeric component was a CF3-meta-isomeric unit centered on the aromatic carbon substituted with the trifluoromethyl group. In particular, the amide acid compound was determined to be composed of 80 mol % CF3-meta-isomer and 20 mol % H-meta-isomer. Therefore, for the poly(amic acid)s, the minor isomeric component is speculated to be a H-meta-isomeric unit rather than a para-isomeric unit. The result might result mainly from the strong electron-withdrawable and bulky trifluoromethyl substituent in the CF3DAN monomer. The strong electron withdrawability might significantly enhance the reactivities of the adjacent carbons in the monomer to the nucleophilic attack of the amino nitrogen in the aniline and diamines, and consequently overcome the role of the bulkyness, ultimately leading to the amide acid and poly(amic acid)s rich with the CF3-meta-isomeric unit. In addition, a portion of the imide form was detected in the dried AN-CF3DAM-AN amide acid. Thus, the formation of imide linkage might be involved in a small portion for the dried poly(amic acid)s. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1755-1765, 1998
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  • 28
    ISSN: 0887-624X
    Keywords: diaminotetraphenylimidazolinone ; soluble aromatic polyimides ; solubility ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of new soluble aromatic polyimides with inherent viscosities of 0.65-1.12 dL/g were synthesized from 1,3-bis(4-aminophenyl)-4,5-diphenylimidazolin-2-one and various aromatic tetracarboxylic dianhydrides by the conventional two-step procedure that included ring-opening polyaddition and subsequent thermal cyclodehydration. These polyimides could also be prepared by the one-pot procedure in homogeneous m-cresol solution. Most of the tetraphenyl-pendant polyimides were soluble in organic solvents such as N,N-dimethylacetamide, 1,3-dimethyl-2-imidazolidone, and m-cresol. Some polyimides gave transparent, flexible, and tough films with good tensile properties. The glass transition temperatures and 10% weight loss temperatures under nitrogen of the polyimides were in the range of 287-326 and 520-580°C, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1767-1772, 1998
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  • 29
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: rare-earth coordination catalyst ; styrene ; isotactic polystyrene ; neodymium ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymerization of styrene with the neodymium phosphonate Nd(P507)/H2O/Al(i-Bu)3 catalytic system has been examined. The polymer obtained was separated into a soluble and an insoluble fraction by 2-butanone extraction. 13C-NMR spectra indicate that the insoluble fraction is isotactic polystyrene and the soluble one is syndiotactic-rich atactic polystyrene. The polymerization features are described and discussed. The optimum conditions for the polymerization are as follows: [Nd] = (3.5-5.0) × 10-2 mol/L; [styrene] = 5 mol/L; [Al]/[Nd] = 6-8 mol/mol; [H2O]/[Al] = 0.05-0.08 mol/mol; polymerization temperature around 70°C. The percent yield of isotactic polystyrene (IY) is markedly affected by catalyst aging temperature. With increase of the aging temperature from 40 to 70°C, IY increases from 9% to 48%. Using AlEt3 and Al(i-Bu)2H instead of Al(i-Bu)3 decreases the yield of isotactic polystyrene. Different neodymium compounds give the following activity order: Nd(P507)3 > Nd(P204)3 > Nd(OPri)3 > NdCl3 + C2H5OH > Nd(naph)3. With Nd(naph)3 as catalyst, only atactic polystyrene is obtained. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1773-1778, 1998
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  • 30
    ISSN: 0887-624X
    Keywords: carbon monoxide ; norbornene ester ; glass transition temperature ; palladium catalyst ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article we will discuss the synthesis of the new copolymers of norbornene derivatives with an ester group and carbon monoxide, using Pd(CH3CN)4(BF4)2 as a catalyst and 2,2′-bipyridine as a ligand in nitromethane/methanol at 60°C. Elementary analysis, infrared spectra, and NMR spectra indicated that copolymers contain ketone, ester, and bicyclic structures. Methanol functions as the coinitiator and chain transfer agent in copolymerization. A decrease in the molar ratio of [CH3OH]/[Pd] caused an increase in molecular weight and a decrease in yield of the copolymer. The number-average molecular weight of copolymers (Mn) ranged from 3800 to 5300, and the glass transition temperature (Tg) ranged from -32 to 117°C. Thermal analysis revealed that both T10%d and Tmaxd exceeded 180 and 230°C, respectively. Linear long-chain substituents such as n-C11H23C(O)—O—CH2— drastically reduced Tg to a value of -32°C. In general, copolymers having a longer linear side-chain substituents of ester on norbornene have a more desirable solubility. Moreover, X-ray diffraction demonstrated that the degree of crystallinity decreases with an increasing length of side chain substituents. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1785-1790, 1998
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  • 31
    ISSN: 0887-624X
    Keywords: poly(sulfonium salt) ; poly(2-vinyldibenzothiophene) ; 5-methyl-2-vinyldibenzothiophenium tetrafluoroborate ; sulfonium monomer ; radical polymerization ; polymer reaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A polymer having dibenzothiophenium salt moieties [poly(sulfonium salt), 2] was prepared by the reaction of poly(2-vinyldibenzothiophene) (1) with CH3I and AgBF4 in CH2ClCH2Cl at room temperature for 24 h. The obtained polymer 2 was found to contain 71% of the methyldibenzothiophenium tetrafluoroborate unit. A monomer carrying the sulfonium salt moiety, i.e., 5-methyl-2-vinyldibenzothiophenium tetrafluoroborate (4), was independently prepared and subjected to radical polymerization to give a polymer (5) in 88% yield (methyldibenzothiophenium tetrafluoroborate unit: 79%). The thermal decompositions of 2 and 5 took place in two steps; the first step involved the formation of polymer 1 by demethylation. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1779-1784, 1998
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  • 32
    ISSN: 0887-624X
    Keywords: liquid crystalline polymers ; copoly(ester imide)s ; smectic ; nematic ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel liquid crystalline copoly(ester imide)s were synthesized via polyesterification of triethyleneglycol bis(4-carboxyphenyl) ether (1e), diacetoxybiphenyl, and diacids with imide moieties. The effects of composition on the changes of Tg, Tm, and Ti were examined by global TSC and DSC. Thermal gravimetric analyses (TGA) found that 4a-d and 5a-g possess higher thermal stability. Strong stir opalescence phenomenon and observations from polarized optical microscopy identified that 2b-e and 3a-d possess the typical schlieren texture of an enantiotropic nematic mesophase. The birefrigent melts of 4a-d and 5a-g, however, displayed particular liquid crystalline behavior. Copolymers with higher aromatic imide ring content (4a-d, 5a-g) form a layered structure and an enantiotropic smectic mesophase in the melting state. The melt viscosity of the semetic mesophase was higher than the nematic mesophase which was observed by capillary rheometer. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1791-1803, 1998
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  • 33
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polycaprolactone ; irradiation ; graft copolymerization ; acrylic acid ; preirradiation grafting ; electron beam ; EB ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acrylic acid was grafted onto poly(ε-caprolactone) (PCL) films by using electron beam (EB) preirradiation technique. The effect of reaction time, monomer concentration, radiation dose, time between irradiation and grafting, radiation atmosphere, and polymer crystallinity on the extent of grafting were studied. Silver and tin ions were attached to the grafted chains in order to study the grafting process. The irradiation in air was initially more rapid, but the final extent of grafting was the same when irradiated in nitrogen atmosphere. Maximum grafting extents exceeding 400% could be obtained. The optimal grafting was obtained at an acrylic acid to water ratio of 30 : 70. The grafting process could be initiated at a dose as low as 12 kGy. The grafting process proved to start at the surface and was extended into the bulk with time. The ability to form crystals was reduced as the grafting extent increased. The water uptake of the poly(ε-caprolactone)-graft-poly(acrylic acid) was increasing with increasing grafting extent, but reached a maximum of ca 100% for all grafting extents above 85%. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1805-1812, 1998
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  • 34
    ISSN: 0887-624X
    Keywords: morphology ; grafting ; oxazoline-functionalized polymer particles ; carbolic acids ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxazoline-functionalized, crosslinked PMMA-particles, prepared by free radical nonaqueous dispersion polymerization, were grafted with n-decanoic acid and carboxylic acid-terminated polystyrene. Oxazoline groups, separated by an alkylspacer from the PMMA backbone, showed enhanced mobility with respect to the backbone, as evaluated by solid-state NMR spectroscopy using a dipolar filter. As a function of molecular mass of the carboxylic acid, the oxazoline conversion varied from 70 mol % for n-decanoic acid to 1% for monocarboxylate-terminated polystyrene CT-PS with Mn: 15,900 g/mol. Morphological studies, performed by TEM, showed that reaction with acid terminated polystyrene results exclusively in interfacial grafting at the particle surface. At low grafting levels a raspberry-like morphology was obtained, whereas grafting levels exceeding 14 wt % CT-PS resulted in core-shell morphology. Core-shell morphology was also verified by static light scattering using toluene solvent, which is isorefractive to the PMMA core. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1821-1827, 1998
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  • 35
    ISSN: 0887-624X
    Keywords: surface modification ; argon plasma treatment ; poly(ethylene) ; poly(propylene) ; poly(cis-butadiene) ; carboxylic acid groups ; XPS ; SSIMS ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article, a study on the mechanism of the immobilization of surfactants on polymeric surfaces by means of an argon plasma treatment is described. The unsaturated surfactant sodium 10-undecenoate [C11(:)] and the saturated surfactant sodium dodecanoate (C12) were immobilized on poly(ethylene) (PE), poly(propylene) (PP), and poly(cis-butadiene) (PB) surfaces. This was accomplished by treating polymeric substrates that were coated with C11(:) or C12 with an argon plasma. Derivatization X-ray Photoelectron Spectroscopy (XPS) and Static Secondary Ion Mass Spectrometry (SSIMS) showed that during the plasma treatment surfactants were covalently coupled to the polymeric surfaces. The chemical structure of both the surfactant and the polymeric substrate influenced the immobilization efficiency. At an optimal treatment time of 5 s, about 28 and 6% of the initial amount of carboxylate groups in the precoated C11(:) and C12 layer, respectively, was retained at the PE surface. The immobilization efficiencies of C11(:) and C12 on PP were about 20 and 9%, respectively. The immobilization efficiency of C11(:) and C12 on PB were both about 7%. The results obtained in this study indicate that the immobilization proceeds via a radical mechanism. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1829-1846, 1998
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  • 36
    ISSN: 0887-624X
    Keywords: 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride ; poly(ether imide)s ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new naphthalene unit-containing bis(ether anhydride), 2,6-bis(3,4-dicarboxyphenoxy)naphthalene dianhydride, was synthesized in three steps starting from the nucleophilic nitrodisplacement reaction of 2,6-dihydroxynaphthalene and 4-nitrophthalonitrile in N,N-dimethylformamide (DMF) solution in the presence of potassium carbonate, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). High-molar-mass aromatic poly(ether imide)s were prepared using a conventional two-step polymerization process from the bis(ether anhydride) and various aromatic diamines. The intermediate poly(ether amic acid)s had inherent viscosities of 0.65-2.03 dL/g. The films of poly(ether imide)s derived from two rigid diamines, i.e. p-phenylenediamine and benzidine, crystallized during the thermal imidization process. The other poly(ether imide)s belonged to amorphous materials and could be fabricated into transparent, flexible, and tough films. These aromatic poly(ether imide) films had yield strengths of 104-131 MPa, tensile strengths of 102-153 MPa, elongation to break of 8-87%, and initial moduli of 1.6-3.2 GPa. The glass transition temperatures (Tg's) of poly(ether imide)s were recorded in the range of 220-277°C depending on the nature of the diamine moiety. All polymers were stable up to 500°C, with 10% weight loss being recorded above 550°C in both air and nitrogen atmospheres. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1657-1665, 1998
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  • 37
    ISSN: 0887-624X
    Keywords: polyhydrazides ; poly-1,3,4-oxadiazoles ; thermal behavior ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two flexible dicarboxylic acid monomers, 4,4′-[isopropylidenebis(1,4-phenylene)dioxy]dibenzoic acid (1) and 4,4′-[hexafluoroisopropylidenebis(1,4-phenylene)-dioxy]dibenzoic acid (3), were synthesized from readily available compounds in two steps in high yields. High molecular-weight polyhydrazides and poly(amide-hydra-zide)s were directly prepared from dicarboxylic acids 1 and 3 with terephthalic dihydrazide (5), isophthalic dihydrazide (6), and p-aminobenzhydrazide (7) by the phosphorylation reaction by means of diphenyl phosphite (DPP) and pyridine in N-methyl-2-pyrrolidone (NMP)/LiCl, or prepared from the diacyl chlorides of 1 and 3 with the hydrazide monomers 5-7 by the low-temperature solution polycondensation in NMP/LiCl. Less favorable results were obtained when using triphenyl phosphite (TPP) instead of DPP in the direct polycondensation reactions. Except for those derived from terephthalic dihydrazide, the resulting polyhydrazides and poly(amide-hydrazide)s could be cast into colorless, flexible, and tough films with good tensile strengths. All the hydrazide polymers and copolymers are amorphous in nature and are readily soluble in various polar solvents such as NMP and dimethyl sulfoxide (DMSO). Their Tgs were recorded in the range of 162-198°C and could be thermally cyclodehydrated into the corresponding polyoxadiazoles and poly(amide-oxadiazole)s approximately in the region of 300-380°C, as evidenced by the DSC thermograms. The oxadiazole polymers and copolymers showed a dramatically decreased solubility and higher Tg when compared to their respective hydrazide prepolymers. They exhibited Tgs of 190-216°C and were stable up to 450°C in air or nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1847-1854, 1998
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  • 38
    ISSN: 0887-624X
    Keywords: helical conformation ; stereospecific polymerization ; isotactic ; polyacetaldehyde ; polytrifluoroacetaldehyde (polyfluoral), polytrichloro-acetaldehyde (polychloral) ; polytribromoacetaldehyde (polybromal) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Minimum potential energy helical conformations for a family of four isotactic polyacetaldehydes have been determined. Our results indicate that all of the polymers form irrational helices. Comparisons have been made with the reported structures for two of these stereoregular polymers based on earlier X-ray diffraction data. c-Axis values associated with the pitch of the helix for polyacetaldehyde and for polytrichloroacetaldehyde (polychloral) were experimentally measured to be 0.48 and 0.51 nm, respectively. Our calculated conformations afforded values for a helix pitch of 0.47 and 0.52 nm, respectively, which derive from a 3.9/1 helix for polyacetaldehyde and a 3.7/1 helix for polychloral. The structure for polytribromoacetaldehyde (polybromal) was predicted to be similar to that for polychloral. For polytrifluoroacetaldehyde (polyfluoral) and polyacetaldehyde, a number of helical conformations with similar energies were found. All of these conformations could be related to the polychloral helical structure. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1855-1860, 1998
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  • 39
    ISSN: 0887-624X
    Keywords: blend film ; poly (L-lactic acid) ; cellulose ; enzymatic degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Blend films of poly(L-lactic acid) (PLLA) and cellulose with various composition was prepared by casting from trifluoroacetic acid solution. One hydroxyl group per each glucose unit was esterified by trifluoroacetic acid. The trifluoroacetyl group was hydrolyzed completely during the degradation. Weight losses for 90/10 and 75/25 PLLA/cellulose blends by proteinaze K were greatly increased compared with pure PLLA sample due to the large depression of the crystallinity of PLLA component, while cellulase was effective only for the degradation of pure cellulose film. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1861-1864, 1998
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  • 40
    ISSN: 0887-624X
    Keywords: anionic polymerization ; poly(2-hydroxyethyl methacrylate) ; amphiphilic block copolymer ; poly(methyl methacrylate)-b-poly(2-hydroxyethyl methacrylate) ; poly(styrene)-b-poly(2-hydroxyethyl methacrylate) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vinyl of the ester group of 2-vinyloxyethyl methacrylate was first selectively reacted with acetic acid to obtain 2-[1-(acetoxy)ethoxy]ethyl methacrylate (2). This protected monomer was subjected to anionic polymerization in tetrahydrofuran at -60°C in the presence of LiCl, using 1,1-diphenylhexyllithium as initiator. The molecular weight of the polymer could thus be controlled and a narrow molecular weight distribution obtained. The protecting group, 1-(acetoxy)ethyl, could be easily eliminated (by quenching the polymerization reaction with methanol and water) to generate poly(2-hydroxyethyl methacrylate) (poly(HEMA)). Block copolymers were also prepared by the sequential anionic polymerization of MMA and 2 or styrene and 2. They possess narrow molecular weight distributions, and controlled molecular weights and compositions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1865-1872, 1998
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  • 41
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: polycarbonate ; poly(methyl methacrylate) ; blends ; exchange reactions ; mass spectrometry ; thermal degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical reactions occurring in the thermal treatment of bisphenol-A polycarbonate (PC) and poly(methyl methacrylate) (PMMA) blends have been investigated by nuclear magnetic resonance (NMR), mass spectrometry (MS), size exclusion chromatography (SEC), and thermogravimetry (TG). Our results suggest that in the melt-mixing of PC/PMMA blends, at 230°C, no exchange reactions occur and that only the depolymerization reaction of PMMA has been observed. In the presence of an ester-exchange catalyst (SnOBu2), an exchange reaction was found to occur at 230°C, but no trace of PC/PMMA graft copolymer has been observed. Instead, an exchange reaction between the monomer methyl methacrylate (MMA), generated in the unzipping of PMMA chains, and the carbonate groups of PC has been suggested. This is due to the diffusion of MMA at the interface or even into the PC domains, where it can react with PC producing low molar mass PC oligomers bearing methacrylate and methyl carbonate chain ends and leaving the undecomposed PMMA chains unaffected. The TG curves of PC/PMMA blends prepared by mechanical mixing and by casting from THF show two separated degradation steps corresponding to that of homopolymers. This behavior is different from that of a transparent film of PC/PMMA blend, obtained by solvent casting from DCB/CHCl3, which shows a single degradation step indicating that the degradation rate of PC is increased by the presence of PMMA in the blend. The thermal degradation products obtained by DPMS of this blend consist of methyl methacrylate (MMA), cyclic carbonates arising from the degradation of PMMA and PC, respectively, and a series of open chain bisphenol-A carbonate oligomers with methacrylate and methyl carbonate terminal groups. The presence of the latter compounds suggests a thermally activated exchange reaction occurring above 300°C between MMA and PC. The presence of bisphenol-A carbonate oligomers bearing methyl ether end groups, generated by a thermally activated decarboxylation of the methyl carbonate end groups of PC, has also been observed among the pyrolysis products. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1873-1884, 1998
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  • 42
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: phthalonitrile monomer ; thermoset ; curing agent ; processability ; thermal stability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phthalonitrile monomers can be polymerized thermally in the presence of small amounts of curing agents into thermosetting polymers. The thermosets exhibit outstanding thermo-oxidative stability, display good mechanical properties, and offer promise as matrices for composite applications. The phthalonitrile cure reaction is typically accomplished with an aromatic diamine, 1,3-bis(3-aminophenoxy)benzene (m-APB), added in the range of 1.5-2% by weight of the monomer in the melt phase. This article addresses the cure reaction with a sulfone-containing diamine, bis[4-(4-aminophenoxy)phenyl] sulfone (p-BAPS), which shows lower volatility as determined from thermogravimetric studies (TGA) compared to m-APB at the processing temperatures typically employed for phthalonitrile cures. Rheometric studies conducted to monitor the viscosity increase during a cure reaction suggest that the cure reaction with m-APB is faster compared to the reaction with p-BAPS. Even though differences are seen in the initial cure rates, the final cured products are similar in terms of the glass transition temperatures and thermal and oxidative stabilities. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1885-1890, 1998
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  • 43
    ISSN: 0887-624X
    Keywords: polyisobutylene ; poly(dimethylsiloxane) ; hydrosilation ; bicomponent networks ; molecular weight between crosslinks ; network functionality ; sol fraction ; extractables ; model networks ; end-linking ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel polyisobutylene (PIB)/poly(dimethylsiloxane) (PDMS) bicomponent networks is described. The synthesis strategy (see Figure 1) was to prepare well-defined and -characterized allyl-tritelechelic polyisobutylenes [φ(PIB - C - C=C)3] and SiH-ditelechelic poly(dimethylsiloxanes) (HSi-PDMS-SiH) and then crosslink these moieties by hydrosilation. The φ(PIB - C - C=C)3 was prepared by living isobutylene polymerization followed by end-quenching with allyltrimethylsilane, whereas the HSi-PDMS-SiH was obtained by equilibrium polymerization of octamethylcyclotetrasiloxane and tetramethyldisiloxane. The detailed structures of the starting polymers were characterized by GPC and 1H-NMR spectroscopy. A series of PIB/PDMS bicomponent networks of varying compositions and average molecular weights between crosslinks (Mc) of ∼ 20,000 g/mol were assembled. Optimum crosslinking conditions were defined in terms of H2PtCl6 catalyst concentration, nature of solvent, time, temperature, and stoichiometry of ∼ CH2CH=CH2/∼SiH groups, allowing for the convenient synthesis of well-defined model bicomponent networks. Swelling studies and elemental analysis confirm the correctness of the synthetic strategy. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1891-1899, 1998
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  • 44
    ISSN: 0887-624X
    Keywords: polyisobutylene ; poly(dimethylsiloxane) ; bicomponent networks ; network structure ; molecular weight between crosslinks ; network properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first part of this series concerned the synthesis of novel polyisobutylene (PIB)/poly(dimethylsiloxane) (PDMS) bicomponent networks; the present paper concerns the structure and property characterization of a series of bicomponent networks of varying compositions (PIB wt %/PDMS wt % = 92/8, 70/30, 50/50, 35/65) having average molecular weights between crosslinks (Mc) of ˜ 20,000 g/mol. According to network structure analysis by uniaxial equilibrium stress-strain measurements, the experimental Mc's are in excellent agreement with theoretical values. Hydrosilation end-linking efficiency was quantitated by the amount of sol and functional group analysis by 1H-NMR spectroscopy. NMR evidence indicates double-bond isomerization during hydrosilation. Network compositions by elemental analysis together with the low sol fractions indicate efficient crosslinking. These data suggest highly efficient network formation and well-defined bicomponent network structures. While PIB and PDMS showed Tg's at -72 and -124°C, respectively, the bicomponent network did not exhibit clearly discernible phase transitions. The heat stability of bicomponent networks increased slightly with increasing PDMS content showing initial (10%) degradation temperatures at ˜ 380°C in nitrogen and ˜ 320°C in air. Tensile strengths and elongations were dependent on composition and varied in the 0.6-3.8 MPa and 600-1100% ranges, respectively. The swelling behavior was not much affected by composition. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1901-1910, 1998
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  • 45
    ISSN: 0887-624X
    Keywords: living polymerization ; radical polymerization ; oxoaminium salt ; nitroxide ; chlorine-attached polystyrene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An oxoaminium chloride that is prepared by reacting 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) with chlorine in carbon tetrachloride initiates radical polymerization of styrene at 120°C. In the early stages of polymerization, a monomeric adduct, 2,2,6,6-tetramethyl-1-(2-chloro-1-phenylethoxy)piperidine, is formed. Thereafter, styrene polymerization exhibiting the characteristics of living polymerization proceeds. High molecular weight polymers with relatively narrow molecular weight distributions are obtained by this polymerization. 1H-NMR spectra of the polymers reveal that a chlorine atom and a TEMPO group are present at the α- and ω-termini, respectively. The monomeric adduct was prepared by heating the oxoaminium chloride and styrene in carbon tetrachloride at 65-70°C, and was characterized by 1H- and 13C-NMR spectroscopy. It was found to be suitable as an initiator for nitroxide-mediated radical polymerization of styrene to make polymers with chlorine on the chain end. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2555-2561, 1998
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  • 46
    Electronic Resource
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: thioxanthone derivatives ; water-compatible photoinitiator ; absorption spectrum ; fluorescence ; photopolymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six amine-linked thioxanthones, i.e., 2-(2-hydroxy-3-[bis(2-hydroxyethyl)amino]propoxy)thioxanthone (HAPTX) and its 4-methyl, 1,3-dimethyl, 1,4-dimethyl, 3,4-dimethyl, and 1,3,4-trimethyl substituted derivatives, were synthesized as water-compatible photoinitiators and identified with FTIR, MS, NMR, and elementary analysis. The absorption and fluorescence properties were studied. Their photoinitiating polymerization efficiencies were tested with a recording dilatometer utilizing acrylamide as monomer in aqueous solution. The results show that the six amine-linked thioxanthones can independently initiate acrylamide polymerization efficiently without additional external amines as co-initiators. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2563-2570, 1998
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  • 47
    Electronic Resource
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: ultrahigh molecular weight polyethylene (UHMWPE) ; radiation sterilization ; orthopedic prosthesis ; subsurface oxidation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Following gamma irradiation in air which causes bond scission and yields large concentrations of peroxy radicals, maximum oxidation and an increase in crystallinity occurs on the surface of ultrahigh molecular weight polyethylene. Here, bimolecular reactions of peroxy radicals generate carbonyls, mostly ketones. On the polymer surface, peroxy radicals continue to react over time periods of years to generate carbonyls and chain scission. Peroxy radicals in the interior of the polymer abstract hydrogens and form hydroperoxides, inducing chain reactions and a slow but continue increase of ketone. Within the polymer sample, to a decreasing depth with increasing dose, a reduced concentration of oxygen is available to react with radiolytic radicals, so that more efficient crosslinking and a low level of hydroperoxide chain reaction occur. After long periods of time a surface maximum in carbonyl concentration is produced. Heating polyethylene in high pressures of oxygen accelerates the oxidative process. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 329-339, 1998
    Additional Material: 11 Ill.
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  • 48
    ISSN: 0887-624X
    Keywords: Smith-Ewart theory ; numerical solution ; suspension polymerization ; SPG membrane emulsification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 49
    ISSN: 0887-624X
    Keywords: copolymerization ; divinyl monomers ; diethyl fumarate ; maleic anhydride ; divinylbenzene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The process of formation of reticular copolymer molecular structures produced in free radical copolymerization of divinyl monomers (divinyl ethers of diethylene glycol and hydroquinone, divinyl sulfide, p-divinylbenzene, etc.) with maleic and fumaric acid derivatives is studied. The basic factor that determines the features of molecular and network structures of copolymers is reactivity of the divinyl monomer in copolymerization with monovinyl monomer. The network of copolymers of maleic anhydride with the divinyl ether of hydroquinone is formed out of oligomer microgels. Divinyl sulfide in copolymerization with maleic acid is disposed to cyclocopolymerization; also crosslinking reactions occur. Formation of a network structure of copolymers of divinylbenzene with maleic and fumaric acid derivatives is shown to proceed via an alternating copolymerization mechanism. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 371-378, 1998
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  • 50
    ISSN: 0887-624X
    Keywords: selenium containing polymers ; poly(disulfide) polymers ; 1,2-ethanedithiol oxidation ; nuclear magnetic resonance ; Raman spectroscopy ; selenotrisulfide/disulfide chain and ring polymers ; mechanism of formation of selenotrisulfide polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 1,2 ethanedithiol (EDT) with selenous acid in water or alcohol leads to selenopolysulfide chains or cycles, (C2H4SSeSC2H4SS)n, with randomly distributed —SSeS— and —SS— moieties. The reaction in water produces incompletely reacted material, which on recrystallization, gives an oligomer corresponding to 5 EDT units (pentamer) as confirmed by molecular mass determination, Se analysis, 1H- and 77Se-NMR spectroscopy. In both the pentamer and cyclic forms the incidence of neighboring —SSeS— moieties is higher than that expected statistically. The mechanism for the reaction of thiols with selenous acid provides some rationalization for this observation in as much as neighboring —SSeS— groups, or groups that will lead rapidly to neighboring —SSeS— groups are formed in general before —SS— links can be formed. The Raman spectrum of these products show typical strong SS, SeS, and CS stretching bands at 510, 370, and 730 cm-1. The high frequency of νCS is attributed to a preferred gauche conformation at the CS bonds. For comparison, polydisulfides were also prepared from EDT and iodine in methanol. These products consist of at least seven cyclic polymers ranging from the four-membered 1,2-dithietane to higher members. Heating above 100°C in chloroform for several hours gives a solution containing the four lowest molecular mass rings, which on standing for 24 h, precipitate highly insoluble material, which is probably chain or large-ring polymer. Molecular mass determination in camphor indicates that, like yellow sulphur, chain polymers are formed at the melting point of camphor (170°C). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 379-390, 1998
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  • 51
    ISSN: 0887-624X
    Keywords: cardanol ; polyurethane ; thermoplastic polyurethane ; differential scanning calorimetry ; dynamic mechanical thermal analyzer ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel thermoplastic polyurethane was prepared from cardanol, a renewable resource and a waste of the cashew industry. Cardanol was recovered from cashew nut shell liquid (CNSL) by double vacuum distillation. It was characterized by CHN analysis and IR, 1H-NMR, and 13C-NMR spectroscopy techniques. Cardanol is a meta-substituted long chain phenol. The long aliphatic chain unit substituent was found to be a monoene. The monomer, 4-[(4-hydroxy-2-pentadecenylphenyl)diazenyl]phenol was prepared from cardanol. It was a dihydroxy compound as characterized by CHN analyzer, UV, and 1H-NMR spectroscopy. The polyurethane was synthesized from this dihydroxy compound by the treatment with 4,4′-diphenylmethane diisocyanate (MDI) in dimethylformamide (DMF) solvent at 80-90°C under nitrogen atmosphere. The polymer was characterized by 1H-NMR, FTIR, and UV spectroscopy. The elemental analysis was done for determining the percentage content of C, H, and N, and the intrinsic viscosity [η] of polymer showed 1.85 dL/gm. Thermogravimetric investigations (TGA) of the cardanol, the dihydroxy compound, and the polyurethane were performed to study their decomposition. The semicrystalline nature of the PU was confirmed by differential scanning calorimetry (DSC) and dynamic mechanical thermal analyzer (DMTA). The wide-angle X-ray diffraction (WAXS) study of PU shew a broad amorphous halo indicative of absence of crystallinity in the polymer, which has been explained as due to strong hydrogen bonding in the hard phase. PU may possibly be useful as a telecommunication and as a nonlinear optical material. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 391-400, 1998
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  • 52
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    Bognor Regis [u.a.] : Wiley-Blackwell
    ISSN: 0887-624X
    Keywords: novolac resin ; poly(ethylene oxide) ; interpolymer complexes ; crosslinkable ; polymer morphology ; thermal properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Crosslinkable interpolymer complexes of novolac resin and poly(ethylene oxide) (PEO) were prepared by mutual mixing ethanol solutions of novolac and PEO. Fourier transform infrared (FTIR) studies revealed that the driving force for the formation of novolac/PEO complex is hydrogen bonding interaction between the hydroxyl groups of novolac and the ether oxygens of PEO. The morphology and thermal properties of the complexes before and after curing were investigated by optical microscopy and differential scanning calorimetry (DSC). It was found that the uncured novolac/PEO complexes had a single composition-dependent glass transition temperature (Tg). The curing with 15 wt % hexamine (HMTA) (relative to novolac content) resulted in disappearing of Tg behaviour for both the neat novolac and the novolac-rich complexes, owing to less mobility of the novolac chain segments. The melting temperature (Tm) and crystallization rate of the HMTA-cured novolac/PEO complexes decreased with increasing novolac content, and no Tm was observed for the cured complexes with PEO content less than 50%. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 401-411, 1998
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  • 53
    ISSN: 0887-624X
    Keywords: polyamines ; 4,5-dicyanoimidazoles ; cyclic voltammetry ; quasi-reversible ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2-(1-methyl-4,5-dicyanoimidazolyl) group was attached to poly(diallylamine) and polyethylenimine, affording polymers containing an electron-withdrawing pendant group. The key to their preparation is high reactivity of 1-methyl-2-fluoro-4,5-dicyanoimidazole (1) toward nucleophilic aromatic substitution (NAS) reactions with aliphatic amines. Cyclic voltammograms of these polymers show reduction waves at -2.6 to -2.7 V vs. Ag/Ag+ but no reoxidation waves, unlike those of monomeric and oligomeric model compounds, which are quasi-reversible. The cyclic voltammetry studies of oligomeric model compounds with different alkyl spacers show that the degree of quasi-reversibility decreases as dicyanoimidazoles are crowded together in a molecule, suggesting that a certain degree of chemical reaction occurs between reduced dicyanoimidazole groups. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2619-2629, 1998
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  • 54
    ISSN: 0887-624X
    Keywords: microemulsion polymerization ; seeded polymerization ; butyl acrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The seeded microemulsion polymerization of butyl acrylate was studied with γ-rays. The hydrodynamic diameter and its distribution of polymer particles in the seeded microemulsion before and after polymerization were determined with photon correlation spectroscopy (PCS). Though there were micelles in the microemulsion, it was found that new particle formation could be ignored during polymerization. The polymerization kinetics of the seeded microemulsion was investigated. The polymerization rate increases with the dose rate and added monomer content and decreases with the seed fraction. It was completely different from that for seeded emulsion polymerization. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2631-2635, 1998
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  • 55
    ISSN: 0887-624X
    Keywords: benzocyclobutene ; cesium fluoride ; 4-hydroxybenzocyclobutene ; 4-trimethylsiloxybenzocyclobutene ; thermosets ; arylene ether monomers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of new bis-benzocyclobutene-endcapped arylene ether monomers was prepared and characterized. Whereas 2,6-bis(4-benzocyclobutenyloxy)benzonitrile (BCB-EBN) could be prepared in good yield using the standard procedure (K2CO3/NMP/toluene/Dean-Stark trap/120°C), other bis(benzocyclobutene) (BCB)-terminated monomers containing ether-benzophenone (BCB-EK), ether-phenylsulfone (BCB-ES), and ether-6F-benzoxazole (BCB-EBO) moieties were invariably contaminated by mono-endcapped products under similar reaction conditions. This can be attributed to a much greater activating effect of the nitrile group on the ortho-fluorides in the aromatic nucleophilic displacement reaction than the carbonyl, sulfonyl, and benzoxazolyl groups. However, the latter monomers could be synthesized (70-80%) from 4-trimethylsiloxybenzocyclobutene and respective aromatic fluorides in the presence of CsF at 140°C. Similar curing behaviors under N2 (DSC: extrapolated onset and peak temperatures at 227-230° and 260-262°C, respectively) characterized all four monomers. BCB-EK, BCB-ES, and BCB-EBN showed melting transitions at 108, 119, and 146°C, in that order. As BCB-EBO contained more rigid benzoxazole segments, it only exhibited a glass transition (Tg) at 85°C prior to curing exotherm, after it had been previously heated to 125°C. The following Tgs were observed for the cured materials: BCB-EK (201°C), BCB-EBN (224°C), BCB-ES (264°C), and BCB-EBO (282°C). The relative thermal stability according to TGA (He) results is: BCB-ES < BCB-EBN < BCB-EK < BCB-EBO. Finally, the results from thermal analysis, infrared spectroscopic, and variable temperature microscopic studies indicated that the nitrile group plays an important role in the cure chemistry, thermal, and microstructural properties of BCB-EBN. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2637-2651, 1998
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  • 56
    ISSN: 0887-624X
    Keywords: kinetics ; microwave cure ; thermal cure ; bisnadimide ; crosslinking ; mechanism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetic studies of the crosslinking reaction of a nadic end-capped imide model compound, N,N′-(oxydi-3,4′-phenylene) bis(5-norbornene-2,3-dicarboximide), a bisnadimide, in thermal and microwave processes were investigated. The conversion of the endo isomer to exo isomer proceeds at a much lower temperature than the crosslinking reaction. The crosslinking reaction was monitored by the combined decrease in the infrared absorptions of the endo and exo isomers at 840 and 780 cm-1, respectively. The decrease in the concentration of starting materials follows first-order kinetics in the thermal and microwave processes. At the same temperatures (230 or 280°C), the crosslinking reaction proceeds at about 10 times faster in the microwave process than in the thermal process. Solid-state 13C-NMR showed no significant loss in C=C double bond resonance in the cured products by comparison with the starting material. This study provides direct evidence that the microwave process may be an efficient method to cure nadic end-capped polyimides. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2653-2665, 1998
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  • 57
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    Bognor Regis [u.a.] : Wiley-Blackwell