Abstract

A nematic side-chain liquid-crystalline polymer (SCLCP) was synthesized by grafting a liquid-crystalline monomer, 6-[(4-cyano-4‘-biphenyl)oxy]hexanoic acid (5CN-COOH), onto a nearly monodisperse hydroxylated polyisoprene. The linear dynamic viscoelasticity, steady shear flow, transient and intermittent shear flows, and stress relaxation of the SCLCP in the nematic state were investigated. For comparison, the rheological behavior of a main-chain liquid-crystalline polymer (MCLCP) was also investigated. Similarities and dissimilarities in the rheological behavior between the SCLCP and MCLCP are presented. Some of the important similarities observed are as follows. Upon start-up of shear flow, both SCLCP and MCLCP exhibited a very large overshoot peak of first normal stress difference (N1+ ) and shear stress (σ+ ). The values of first normal stress difference in steady shear flow were positive in both SCLCP and MCLCP over the entire range of shear rates tested. Some of the important dissimilarities observed ...

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