MODEL POLYURETHANE ELASTOMERS PREPARED FROM NONCRYSTALLIZABLE POLY(PROPYLENE OXIDE) CHAINS

In the reported experiments, elastomers of controlled molecular structure were prepared from hydroxyl-terminated atactic poly(propylene oxide) (PPO) chains having number-average molecular weights M//n in the range 800-4360 g mole** minus **1. The chains were end-linked into noncrystallizable trifunctional networks using a specially prepared aromatic triisocyanate. The networks thus obtained were studied with regard to their equilibrium swelling in benzene at 61 degree C. The values of the high deformation modulus are in good agreement with recent molecular theories as applied to the nonaffine deformation of a ″phantom″ network. The values of the low deformation modulus were considerably smaller than the values predicted for an affine deformation, however, suggesting that the junction points were not firmly embedded in the network structure. The swelling equilibrium results were in very good agreement with the new theory of network swelling developed by Flory.