The Influence of Hydrogen Bonding on the Mesomorphic Properties of Side Chain Type Liquid Crystalline Polyurethanes with Rigid Moieties in the Polymer Backbone

Abstract

ABSTRACT:In order to clarify the effect of the specific interaction of hydrogen bonding between urethane bonds (H-bonding) on the mesomorphic properties for side chain type liquid crystalline polyurethanes with a rigid moiety in the polymer backbone (rigid SLCPUs), side chain type polyurethane derivatives where hydrogen in urethane bonds were replaced with methyl groups were prepared by two synthetic routes, namely polycondensation and polymeric reaction. Their thermal properties were investigated by polarizing optical microscopy and differential scanning calorimetry (DSC) measurements. The original rigid SLCPUs exhibited mesomorphic properties, however, no mesomorphic properties were demonstrated in the polyurethane derivatives, regardless of the flexible spacer length. Therefore we concluded that the lateral interaction originating from H-bonding played an important role in the exhibition of mesomorphic properties for the rigid SLCPUs.KEY WORDS Side Chain Type Liquid Crystalline Polymer / Polyurethane / Hydrogen Bonding / Thermal properties of side chain type liquid crystalline polymer (SLCP)s are greatly influenced by mesogenic groups, flexible spacer length introduced between the mesogenic group and polymer backbone, etc. We are interested in the specific interaction which could be organized between the amide group such as polyurethane and/or polyamide derivatives in the polymer backbone. We have already found that mesomorphic properties were exhibited for polyurethanes with a mesogenic group in the side chain. Furthermore, the relationship between the hydrogen bonding (H-bonding) formed by NH group and C = 0 group of the urethane bonds in the polymer backbones and mesomorphic properties for side chain type liquid crystalline polyurethane (SLCPU)s was investigated by thermally controlled FT-IR.

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