Propriétés diélectriques de polysiloxanes cristaux liquides à groupements mésogènes diphényles et espaceurs de type thioéther. Dielectric properties of liquid crystalline polysiloxanes with mesogenic diphenyl groups and thioether spacers

Abstract

SUMMARY: A series of nine liquid crystalline polysiloxanes was studied by means of dielectric spectroscopy. These polymers contain thioether spacers with different length, a diphenyl unit as mesogenic group and end-groups with cyano, nitro or one or two chiral centers. Another liquid crystalline polymer, without sulfur atom in the spacer, was studied in the same conditions. The dynamics of these polymers shows four molecular relaxation (a, ) processes, and a collective (Goldstone mode) relaxation process for chiral polymers. The a relaxation temperature decreases with increasing spacer length due to the sulfur atom. On the other hand, the thioether spacer prevents cristallinity.

Dielectric investigation of interphase formation in composite materials. II. Relaxation process

“…In this way, we show the possibility of using the relaxation process to study molecular motions in, for instance, liquidcrystal polymers (LCPs). 1,2 For side-chain LCPs, the relaxation process in the rubbery state is attributed to the rotational motion of side-chain groups around the main chain. Relaxation behavior has provided some authors a means to study conformational mobility in LCPs.…”