SYNTHESIS AND CHARACTERIZATION OF SIDE-CHAIN LIQUID-CRYSTAL POLYURETHANES

A series of liquid crystal alpha-[bis( 2-hydroxyethyl) amino]-omega-(4 -nitroazobenzene-4'-oxy)alkanes (Cn-diol) with different alkyl chain l ength has been synthesized. All Cn-diols exhibit a smectic phase that has been identified by means of polarizing microscopy and differential scanning calorimetry. These compounds are suitable monomers for the s ynthesis of side-chain liquid crystalline polyurethanes and polyesters . They were polymerized with hexamethylene diisocyanate to correspondi ng SCLC polyurethanes in which the spacer length was varied from 2 to 12 methylene units. Polyurethanes (CnP) with spacer lengths n greater than or equal to 4 exhibited liquid crystalline behavior. Fourier tran sform infrared temperature studies of the CnP were done focusing on H- bonds between the N-H and C=O groups of the urethane backbone. (C) 199 7 John Wiley & Sons, Inc.