NMR INVESTIGATIONS ON A LIQUID-CRYSTALLINE SIDE-CHAIN SILOXANE POLYMER WITH A WIDE BIPHASIC REGION

A polysiloxane bearing two different kinds of side chains has been stu died by nuclear magnetic resonance and relaxation investigations. Both side chains contain the same mesogenic core but differ in their conne ction to the main chain: one of them is bound directly to the backbone , the other is linked to it via a -(CH2)(3)- spacer. In this sample, t he isotropic and mesomorphic phases coexist over a relatively wide ran ge of temperatures. We have tried to explain this phenomenon by microp hase separation. For the s(A)-s(B) transition a similar biphasic behav iour could not be observed with our methods. The order parameter has b een estimated selectively for carbons in different parts of the side c hain (spacer, wing group, mesogenic core). The behaviour of the order parameter in the mesomorphic regions of the biphase was observed, and a possible explanation is given.