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  • Articles  (9)
  • Articles: DFG German National Licenses  (9)
  • Polymer and Materials Science  (7)
  • BIM-23027  (2)
  • 1995-1999  (5)
  • 1990-1994  (4)
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  • Articles  (9)
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  • Articles: DFG German National Licenses  (9)
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  • 1
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: The transesterification reaction in the molten state of ester groups of ethylene vinyl acetate (EVA) copolymers and ethylene acrylic ester (EMA) copolymers has been used to crosslink the chains of this polymeric system. The relative EVA copolymers (or EMA copolymers) concentration dependence of the network formation by co-crosslinking of EVA/EMA miscible blends has been assessed. EVA/EMA networks were characterized by swelling experiments, rheological measurements, and determination of the extent of the reaction through a chromatographic technique. All results can be compared in a master curve. The influence of the polydispersity and the microstructure of EVA and EMA samples was put in evidence. On the other hand, a scaling law (v2∼Mc-3/5) was observed in agreement with predictions of the Flory-Rhener expression. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0887-6266
    Keywords: polyethylene ; poly(butylene terephthalate) ; blend ; rheology ; Palierne's model ; morphology ; differential scanning calorimetry ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystallization at high supercooling of polybutylene terephthalate (PBT) droplets dispersed in a molten polyethylene (PE) matrix was investigated through rheological and DSC experiments. The Palierne's emulsion model was used as a theoretical framework for studying the viscoelastic behavior of the blends in different ranges of temperature: on the one hand, when the two polymers are molten (T 〉 225°C) and on the other hand, when PBT droplets are at high supercooling in the molten PE matrix (130°C 〈 T 〈 205°C). From rheological experimental evidences it was shown that molten and solidified droplets coexist at high supercooling. The Palierne's model was then successfully adapted to take into account the three phases (molten PE, molten PBT droplets, and solidified PBT droplets). The evolution of the behavior with the temperature is consistent with the growing amount of crystallized droplets. Moreover, a calculation taking into account the droplets size distribution and the number of nuclei is introduced to explain the crystallization behavior of three different blend ratios.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2573-2585, 1998
    Additional Material: 9 Ill.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New methacrylic copolymers with prospective second-order nonlinear optical effects are synthesized by radical copolymerization of methyl methacrylate with conjugated zwitterionic methacrylate monomers (2,6-di-tert-butyl-4-[1-(ω-methacryloyloxyalkyl)-4-pyridino]phenolates,1a and 1b). These monomers are obtained via a multi-step reaction. First, 4-(3,5-di-tert-butyl-4-hydroxyphenyl)pyridine (2) is electrosynthesized by an SRN1 reaction in liquid ammonia. Then, this pyridine derivative is N-alkylated by an ω-bromoalkyl methacrylate (5a or 5b) which, in its turn, is obtained by esterification of an ω-bromoalcohol and methacryloyl chloride.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 1432-1912
    Keywords: Somatostatin ; BIM-23027 ; Rat colonic mucosa ; sst2 receptors ; SRIF-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously shown that the somatostatin (SRIF) sst2 receptor-selective peptide, BIM-23027, is a potent antisecretory agent in rat isolated distal colonic mucosa (RDCM) and in radioligand binding studies in RDCM membranes, it only maximally inhibited approximately 40% of [125I]-Tyr11-SRIF-14 binding (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg's Arch Pharmacol 352:402–411). The aim of this study was to characterise the BIM-23027-sensitive and -insensitive SRIF binding sites in more detail and to compare their properties with those of the recombinant sst2 receptor stably expressed in mouse fibroblast (Ltk−) cells. SRIF-14, SRIF-28, CGP-23996 and D Trp8-SRIF-14 abolished [125I]-Tyr11-SRIF-14 binding (pIC50 values, 8.7–9.7) but the competition curves had Hill slopes which were less than unity. Octreotide and L-362,855 inhibited binding over a wide concentration range (0.1 nM-1 μM) and inhibition of binding was incomplete at the highest concentration studied. BIM-23056 (PIC50 〈6.5) was a weak inhibitor of [125]-Tyr11-SRIF-14 binding. GTPγS decreased [125I]-Tyr11-SRIF-14 binding by 40%. Further binding experiments with [125I]-Tyr11-SRIF-14 were carried out in RDCM in the continuous presence of BIM-23027 (1 μM). Under these conditions, seglitide had no effect on [125I]-Tyr11-SRIF-14 binding at concentrations up to 10 μM, whilst SRIF-14 and SRIF-28 abolished specific [125I]-Tyr11-SRIF-14 binding in a manner which was consistent with the ligand binding to two sites. SRIF-14 and SRIF-28 displayed high affinity (pIC50 values of 9.8 and 9.3 respectively) for approximately 70% of these binding sites and low affinity (pIC50 values of 7.8 and 7.3) for the remaining sites. Octreotide, L-362,855 and BIM-23056 were weak inhibitors of [125I]-Tyr11-SRIF-14 binding (PIC50 〈6.5). [125I]-BIM-23027 labelled a single population of SRIF binding sites in RDCM membranes and mouse fibroblast (Ltk−) cells stably expressing the human recombinant sst2 receptor. There was a significant correlation between the affinitestimates of a range of SRIF analogues at inhibiting [125I]-BIM-23027 binding in RDCM membranes and binding to the recombinant sst2 receptor in Ltk− cells, suggesting that the sites labelled by [125I]-BIM-23027 in RDCM are similar to the sst2 receptor. GTPγS (100 μM) decreased [125I]-BIM-23027 binding in RDCM by 60%. The results from these studies demonstrate that [125I]-Tyr11-SRIF-14 labels a heterogeneous population of high affinity SRIF binding sites in RDCM membranes. The majority of these sites are insensitive to GTPγS and display negligible affinity for the cyclic hexapeptides, BIM-23027 and seglitide. The remaining high affinity binding sites can be selectively labelled with [125I]-BIM-23027, are sensitive to GTPγS and show similar characteristics to the recombinant sst2 receptor which appears to mediate the antisecretory effects of SRIF in the mucosa (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg's Arch Pharmacol 352:402–411).
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  • 5
    ISSN: 1432-1912
    Keywords: Key words Somatostatin ; BIM-23027 ; Rat colonic mucosa ; sst2 receptors ; SRIF-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously shown that the somatostatin (SRIF) sst2 receptor-selective peptide, BIM-23027, is a potent antisecretory agent in rat isolated distal colonic mucosa (RDCM) and in radioligand binding studies in RDCM membranes, it only maximally inhibited approximately 40% of [125I]-Tyr11-SRIF-14 binding (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg‘s Arch Pharmacol 352:402–411). The aim of this study was to characterise the BIM-23027-sensitive and -insensitive SRIF binding sites in more detail and to compare their properties with those of the recombinant sst2 receptor stably expressed in mouse fibroblast (Ltk–) cells. SRIF-14, SRIF-28, CGP-23996 and D Trp8-SRIF-14 abolished [125I]-Tyr11-SRIF-14 binding (pIC50 values, 8.7–9.7) but the competition curves had Hill slopes which were less than unity. Octreotide and L-362,855 inhibited binding over a wide concentration range (0.1 nM-1 μM) and inhibition of binding was incomplete at the highest concentration studied. BIM-23056 (pIC50 〈6.5) was a weak inhibitor of [125]-Tyr11-SRIF-14 binding. GTPγS decreased [125I]-Tyr11-SRIF-14 binding by 40%. Further binding experiments with [125I]-Tyr11-SRIF-14 were carried out in RDCM in the continuous presence of BIM-23027 (1 μM). Under these conditions, seglitide had no effect on [125I]-Tyr11-SRIF-14 binding at concentrations up to 10 μM, whilst SRIF-14 and SRIF-28 abolished specific [125I]-Tyr11-SRIF-14 binding in a manner which was consistent with the ligand binding to two sites. SRIF-14 and SRIF-28 displayed high affinity (pIC50 values of 9.8 and 9.3 respectively) for approximately 70% of these binding sites and low affinity (pIC50 values of 7.8 and 7.3) for the remaining sites. Octreotide, L-362,855 and BIM-23056 were weak inhibitors of [125I]-Tyr11-SRIF-14 binding (pIC50 〈6.5). [125I]-BIM-23027 labelled a single population of SRIF binding sites in RDCM membranes and mouse fibroblast (Ltk–) cells stably expressing the human recombinant sst2 receptor. There was a significant correlation between the affinity estimates of a range of SRIF analogues at inhibiting [125I]-BIM-23027 binding in RDCM membranes and binding to the recombinant sst2 receptor in Ltk– cells, suggesting that the sites labelled by [125I]-BIM-23027 in RDCM are similar to the sst2 receptor. GTPγS (100 μM) decreased [125I]-BIM-23027 binding in RDCM by 60%. The results from these studies demonstrate that [125I]-Tyr11-SRIF-14 labels a heterogeneous population of high affinity SRIF binding sites in RDCM membranes. The majority of these sites are insensitive to GTPγS and display negligible affinity for the cyclic hexapeptides, BIM-23027 and seglitide. The remaining high affinity binding sites can be selectively labelled with [125I]-BIM-23027, are sensitive to GTPγS and show similar characteristics to the recombinant sst2 receptor which appears to mediate the antisecretory effects of SRIF in the mucosa (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg‘s Arch Pharmacol 352:402–411).
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 2019-2027 
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: Continuous chemical modification of poly(vinyl chloride) (PVC) with sodium benzene thiolate (NaBT) in a counter-rotating twin screw extruder has been studied. The course of the reaction is analyzed, taking into account the physical changes of the polymer along the length of the screw. From the results, it is concluded that the modification reaction is associated with the fusion-gelation process. The reaction kinetics are determined as a function of the mean residence time with the aid of a UV tracer. Temperature profile, flow rate, and premixing are some of the processing parameters influencing the reaction, kinetics. The continuous modified polymer is analyzed in terms of thermal behavior, molecular weight, and stereochemical structure, and the results are compared with those obtained by a discontinuous melt process (Haake-Rheocord). It is confirmed that the same stereoselective substitution mechanism occurs as that in discontinuous melt with no side reactions.
    Additional Material: 9 Ill.
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  • 7
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: The development of the morphology of a reactive blend along a twin-screw extruder has been experimentally studied. A transesterification reaction activated by a catalyst allowed a cross-linking of the dispersed phase during the flow in the extruder. In comparison with the nonreactive system (without catalysts), the resulting morphologies were characterized by larger dimensions. Influence of screw speed and feed rate were similar for both systems, whereas the changes along the screws were more pronounced for the reactive blend. It appeared that the local morphology was strongly dependent on the extent of the reaction. At low extent, the equilibrium between breakup and coalescence was shifted toward coalescence, whereas at high extent, the classical mechanisms were largely modified and replaced by a “coagulation” mechanism. It was shown that, for the fully cross-linked dispersed phase, the final morphology remained remarkably stable during successive extrusion steps. For such products, the observation of a low-frequency plateau of the elastic modulus suggested the formation of a copolymer at the interface with the matrix. © 1994 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 58 (1995), S. 1393-1399 
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: Thermorheological properties of an incompatible polymer blend of polypropylene inclusions dispersed in a ethylene copolymer matrix were discussed from the emulsion model developed by Palierne. Due to the different rheological behaviors with temperature of the two phases, such a system proved to be a judicious blend in order to consider the special cases of the model applications: (1) the two phases are viscoelastic liquids, (2) the dispersed phase is a solid elastic assimilated to rigid spheres in comparison with viscoelastic liquid behavior of the matrix, and (3) the two phases are elastic solids. At low frequencies, the rheological behavior of the blend was not correctly predicted by the model. So interactions other than hydrodynamics can exist in the intrafacial region, and physical entanglements between the chains of the two constituents leading to topological interactions may be assumed at the interphase. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 9
    ISSN: 0021-8995
    Keywords: 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 , Physics
    Notes: A poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) (80/20 w/w) polymer blend was studied by mechanical spectroscopy. Two relaxations can be distinguished: in the glassy state, a very large secondary relaxation in the range of 100 K to 325 K which results from the combination of secondary relaxations of PVC and PMMA; and only one main relaxation at 364 K associated to the glass rubber transition. The relaxation spectrum in the range of the β relaxation has been described by a relaxation time distribution function based upon a Gaussian function and a series-parallel model. The α relaxation was studied by means of a theoretical approach for the nonelastic deformation of polymers. We found that the miscibility of this blend appears to be a function of the observation scale: the PVC/PMMA blend is heterogeneous at the scale of molecular movements involved for the β relaxation process but homogeneous at the scale of the chain segments responsible for the α relaxation dynamics. © 1996 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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