The nonlinear strain measure of a polyisobutylene (PIB) melt as determined by analysis of uniaxial, planar, ellipsoidal, and equibiaxial extensions is compared to the predictions of the molecular model of Doi and Edwards. It is found that the universal strain function of the Doi-Edwards model is unable to predict the nonlinear behavior of this polymer melt in general extensional flow. The qualitative agreement between predictions and experimental data for the strain dependence of shear stress and first normal stress difference in shear flow that was considered as powerful evidence for the correctness of the Doi-Edwards model seems to be accidental. The exaggerated strain dependence of the model suggests a need to reconsider the assumptions concerning the chain retraction process.Presented at the Golden Jubilee Conference of the British Society of Rheology and Third European Rheology Conference, Edinburgh, 3–7 September, 1990.Dedicated to Professor F.R. Schwarzl on the occasion of his 65th birthday 相似文献
Summary: A new, simple, and effective synthetic method for the preparation of glucose‐terminated polyisobutylenes starting from the corresponding hydroxyl‐terminated polymers is reported. Detailed NMR and matrix‐assisted laser desorption/ionization mass spectrometric (MALDI‐TOF MS) investigations showed the exclusive presence of bis(glucopyranosyl) polyisobutylene. Dynamic light scattering (DLS) investigations of this polymer in solution in both tetrahydrofuran and water showed that microphase separation takes place by the formation of micelles and/or vesicles.
Representative structure of the glucose‐terminated polyisobutylenes synthesized here. 相似文献
Isomerization of the adduct resulting from the protonation of 5-methylene-2-norbornene by trifluoroacetic acid was studied by UC-NMR spectroscopy. Relative rate constants were determined under various experimental conditions. The influence of temperature, solvent, and relative reactant concentrations was examined. 相似文献
Polyisobutylene (PIB) benzyl amine was synthesized by reacting benzyl azide with the dichloroboron head group of PIB obtained by polymerization of isobutylene (IB) via haloboration-initia-tion with boron trichloride. The facile, one-pot reaction at room temperature resulted in quantitative conversion of the PIB dichloroboron head groups into benzyl amine functionality, determined by 1H NMR spectroscopy and titration with per-chloric acid. The hydrogenation of the secondary amine was attempted with various hydrogenation catalysts, of which only palladium yielded primary amine functional PIB. Pt and PtO hydrogenated the benzene ring resulting in PIB cyclohexyl methylene amine. With Pd only about 80% of the chain ends carried the primary amine functional group, apparently due to a side reaction. The side reaction was studied by 1H NMR spectroscopy using PIB benzyl amine prepared from deuterated IB. Although direct evidence was not obtained, the 1H NMR spectrum of the debenzylated product indicates that elimination of the amine group from the α carbon and elimination of a methyl group from the β carbon take place simultaneously, presumably due to the crowded nature of the neopentyl-type structure. The primary amine functional PIB was converted into PIB acetyl amide and imide via acylation with acetyl chloride. The products were analyzed by IR, 1H NMR, and 13C NMR spectroscopy. 相似文献