Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New reaction products have been generated on polyethylene and polystyrene surfaces using a novel two-step process. The first stage involves exposure to a downstream nitrogen plasma, and the second to either ozone or a corona discharge. It is observed that each of the two-step reactions yields very different reaction products, with an apparent increase in the formation of C—O functional groups in the former case and the formation of surface — NO2 groups in the latter case.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0887-624X
    Keywords: tetrafluorobenzene derivatives ; fluorinated polymers ; condensation polymers ; polyesters ; polycarbonates ; polyurethanes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel diol monomer, α,α,α′,α′-tetramethyl-1,4-tetrafluorobenzenedimethanol, has been synthesized by a convenient route which involves the addition of acetone to 1,4-dilithiotetrafluorobenzene and can be purified by washing with hexanes. It does not directly undergo condensation polymerizations with diacid chlorides. Its disodium salt, prepared by its reaction with sodium hydride, similarly fails to undergo such polymerizations readily. However, the dilithium salt, prepared in situ by the reaction of the title diol with 2 equiv of n-butyllithium in tetrahydrofuran, is suitable for the preparation of various classes of condensation polymers. Four polyesters and one polycarbonate derived from the reactions of the dilithium salt of the diol with adipoly dichloride, sebacoyl dichloride, isophthaloyl dichloride, terephthaloyl dichloride, and phosgene and two polyurethanes derived from its reactions with tolylene-2,4-diisocyanate and methylene-di-1,4-phenyl diisocyanate were prepared. Each was fully characterized by GPC, NMR, IR, and UV-visible spectroscopies, and the results of these studies are reported herein. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 0887-624X
    Keywords: plasma ; x-ray photoelectron spectroscopy surface modification ; O3P ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas phase downstream products of an air glow discharge have been measured, using absorption and emission spectroscopies, as a function of plasma power, air flow rate, and distance from the plasma. In addition, the reaction of these products with a linear low density polyethylene (LLDPE) polymer surface has been followed using x-ray photoelectron spectroscopy (XPS). At higher air flow rates (〉300 sccm), the primary reactive species is confirmed to be O(3P) atomic oxygen. Some O(3P) is generated in the plasma itself, but more appears to be formed in the downstream region, because of dissociation of molecules in their excited states. At low flow rates, the concentration of O(3P) is strongly depleted at the sample position, but other atomic oxygen states become more prominent. O(5S) and O(3S) are two states which are identified. XPS studies of the polyethylene surface reacted at high flow rates shows oxygen functionalities that are likely the result of an initiation by hydrogen abstraction. At low flow rates, the products suggest initiation by oxygen insertion. Thus, changes in flow rate can result in major changes to the polymer surface chemistry. © 1996 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1042-7147
    Keywords: Liquid crystaline copolymers ; itaconate mesogen ; transition temperatures ; reactivity ratios ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A mesogenic monomer di-[6-(4-methoxy-4′-biphenyloxy) hexyl]-2-methylene butane-1,4-dioate, has been copolymerized with non-mesogen monomers, one racemic and one optically pure, with a view to examining the potential for using these to induce chiral liquid crystal line phases in the copolymer. This proved to be ineffective, with the copolymer exhibiting only smectic A or smectic B phases. Transition temperature-copolymer composition diagrams have been constructed for both copolymer series and their features have been contrasted. Monomer reactivity ratios have been derived for both copolymer systems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0887-624X
    Keywords: comb-branch liquid crystal ; chiral nematic polymer ; liquid crystal copolymers ; selective reflection colors ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new series of copolymers with optically-active liquid crystalline side chain units has been synthesized from the comonomers (S)-2-[2-(4′-cyano-4-biphenylyloxy-1-methylethoxy]ethyl methacrylate (1) and di[6-(4-methoxy-4′-oxybiphenyl)hexyl]-2-methylene butane-1,4-dioate (4). Chiral nematic phases were exhibited by two members of the series, rich in monomer 1, while a smectic phase was exhibited in copolymers rich in 4. While it was thought possible that ordered chiral liquid crystalline phases may be induced by copolymerizing chiral mesogenic monomers with mesogenic derivatives of itaconic acid where the high side chain density encourages greater ordering in the system, no evidence of smectic C* phases could be found in the present systems. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0887-624X
    Keywords: acrylic esters ; fluorinated acrylates ; polyacrylates ; fluorinated polyacrylates ; fluorinated polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five acrylic esters having different fluorine contents and distributions in their side-groups (i.e., CH2=CHC(O)OR, where R = —C(CH3)2C6F4H, —C(CH3)2C6F5, —C(CF3)2C6F5, —C(CF3)2C6H5, and —C(CH3)2C6H5) have been prepared from the reactions of the lithium salts of their corresponding alcohols with acryloyl chloride. These monomers are polymerized under identical conditions by the radical initiator AIBN and five polyacrylates were prepared having the structure of — [ —CH2CHC(O)OR—]n—. These addition polymers were compared and fully characterized by GPC, VPO, DSC, TGA, NMR, IR, and UV-visible spectroscopies, and they showed potential for practical applications. Significant differences in their thermal stabilities were found with respect to fluorine contents and distributions in these polyacrylates, and the highest stability arises from CF3 substitutions in the side-chains of the polymers. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction rates and products of remote oxygen plasma treatment, corona discharge, and ozone treatment of high and low density polyethylenes have been examined using x-ray photoelectron spectroscopy. The oxygen uptake by remote plasma treatment was faster than that of other surface treatments using excited oxygen species. A steady state concentration of 18 ± 1% oxygen can be attained within 1 s of exposure in the remote plasma.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0887-624X
    Keywords: condensation polymers ; Worganonickel-organosilicon copolymers ; organosilicon polymers ; siloxane polymers ; organometallic polymers ; organonickel complexes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of five novel organonickel-organosilicon alternating copolymers having the repeating unit —C6F4—Ni‘PBu3’2—C6F4—SiR2— [where SiR2 = —SiMe2—, —SiMe‘Hex’—, —SiPh2—, —SiMe2—O—SiMe2—, and —SiMe2—‘CH2’6—SiMe2—] are reported. The model compounds Ni‘PR3’2‘1,4-C6F4SiMe3’2‘PR3 = PMePh2 or PBu3’ were prepared via reactions of Ni‘PR3’2‘1,4-C6F4Li’2 with 2 equiv of SiMe3Cl, and were characterized by conventional analytical and spectroscopic measurements. The Polymers were prepared from the reactions of Ni‘PBu3’2‘1,4-C6F4Li’2 with 1 equivalent of SiMe2Cl2 ‘polymer 1, Mw = 15,800’, SiMe ‘Hex’ Cl2 ‘polymer 2, Mw = 7300’, SiPh2Cl2 ‘polymer 3, Mw = 8600’, O‘SiMe2Cl’2 ‘polymer 4, Mw = 13,900’ and ‘CH2’6‘SiMe2Cl’2 ‘polymer 5, Mw = 19,700’. The molecular weights for each polymer were fully determined by both GPC and VPO. The multinuclear ‘1H-, 19F-, and 31P [1H]’-NMR, FTIR, and UV-Visible spectroscopic data for each polymer unambiguously establishes its repeating unit structure. The observations indicate that introduction of the silyl or siloxane units into the organonickel backbones has remarkably decreased the chain rigidity of the organonickel-organosilicon polymers compared to their rigid rod organonickel analogues ‘i.e., —[—C6F4—Ni‘PR3’2—]n—’. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dilatometric and calorimetric studies have been made of the fusion process of linear polyethylene crystallized by stirring xylene solutions at elevated temperatures. It is shown that the melting point of the crystals increases rapidly from 139.5°C to 145°C in the crystallization temperature range of 100-103°C and levels off to 146 ± 0.5°C, provided that very slow heating rates are employed. Stirrer-crystallized samples treated with fuming nitric acid show higher crystalline contents. Comparison of their enthalpies of fusion and melting points indicate that higher molecular order along the fiber axis is associated with higher crystallization temperatures. This is in general agreement with corresponding results of other modes of crystallization. The attack of fuming nitric acid on stirrer crystals is characterized by weight-loss curves similar to those of dilutesolution crystals and bulk polyethylene. The linear molecular weight dependence on time of exposure to nitric acid suggests that the oxidation proceeds mainly from the chain ends at a constant rate for samples stirred in the lower crystallization range, but an increased rate is observed for a sample stirred from xylene at 105°C. It is suggested that the lamellar overgrowths, most evident at low crystallization temperatures, are epitaxially attached to the fiber axis, whereas the smaller crossbandings observed at higher crystallization temperatures are possibly made up of elements of chains that are only partly incorporated in the highly ordered fibrous core.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0887-6266
    Keywords: side-chain crystallization ; ethylene copolymers ; 13C NMR ; x-ray diffraction ; solid state NMR ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phase structure of random copolymers of ethylene and ethylene-d4 with 1-octadecene and other 1-alkenes has been investigated. CPMAS 13C NMR spectra show that a fraction of the central sections of C16H33 side chains in ethylene-d4 copolymers are in ordered environments at 298 K. They give rise to resonances from 32.9 ppm to 33.8 ppm, which show that they are in trans conformations; T1C values for this group of resonances range from 1 s to 7 s. The remaining side chains are in an amorphous environment, the internal methylenes having a chemical shift of 30.8 ppm and a T1C close to 0.4 s. A Raman band at 1062 cm-1 in the spectrum of an ethylene-d4-1-octadecene copolymer is consistent with partial crystallization of side chains. Some side-chain crystallization also occurs in a 1-tetradecene copolymer. X-ray diffraction studies suggest that smaller side chains do not crystallize to a significant extent at 298 K. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...