Polyisobutylene model elastomers prepared using demonstrably complete end-linking reactions |
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Authors: | P -H Sung S -J Pan J E Mark V S C Chang J E Lackey J P Kennedy |
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Affiliation: | (1) Department of Chemistry and the Polymer Research Center, The University of Cincinnati, 45221 Cincinnati, OH, USA;(2) Institute of Polymer Science, University of Akron, 44325 Akron, OH, USA |
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Abstract: | Summary Linear polyisobutylene (PIB) molecules with either hydroxyl or isopropenyl groups at the chain ends were prepared using cationic polymerizations with bifunctional initiator-chain transfer agents. Extensive spectroscopic analyses confirmed the essentially perfect difunctionality of the two types of polymers. The former polymers were end-linked using an aromatic triisocyanate, and the latter by means of a tetrafunctional silane. The resulting trifunctional and tetrafunctional model PIB networks were found to have absolutely negligible sol fractions, which demonstrates that the end-linking reactions used to prepare them were essentially complete. The networks were studied with regard to their equilibrium stress-strain isotherms in uniaxial extension at 25 °C. The results thus obtained are in satisfactory agreement with theory and yield no evidence whatever for significant elastic contributions from inter-chain entanglements. |
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