Oriented crystallization and contractility in the absence of tension

Axially oriented crystalline polymers of either synthetic or natural origin contract upon melting. Examples are shown in Figs. 8.10 and 8.11 for fibrous natural rubber (16) and for a collagen fiber immersed in water.(42) Here the change in length 

There is a fundamental distinction between Li for networks formed from highly oriented chains as compared with those formed from random ones. In the latter case the network is necessarily isotropic. Hence Li may be identified with the length of the specimen and is independent of the number of chains v which comprise the network. If, however, the chains are sufficiently axially oriented prior to cross-linking, the situation is quite different. As has been indicated previously, L is expected to increase as The predicted increase in isotropic length is substantiated by 

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