Liquid crystalline polymers containing sodium sulfonate groups pendant to the polymer backbone were synthesized by an interfacial condensation reaction of brilliant yellow, a sulfonate-containing monomer, with 4,4'-dihydroxy-a,a'-dimethyl benzalazine and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. Polymers containing up to ca. 4mol% brilliant yellow were characterized by elemental analysis and ultraviolet spectroscopy. The polymers were thermally stable to about 300℃, and they exhibited a broad nematic mesophase region of 70-100℃. The solution viscosity behavior in chloroform suggested that intramolecular associations of the sulfonate groups occurred at low polymer concentrations and internolecular associations predominated at higher concentrations.

Liquid crystalline ionomers containing sulfonate groups on the terminal unit of the chain were synthesized by an interfacial condensation reaction of 4,4'-dihydroxy-a,a'-dimethyl benzalazine, the monofunctional dye fast yellow (FY), and a 50/50 mixture of sebacoyl and dodecanedioyl dichlorides. The weight-average molecular weights were estimated from inherent viscosity measurements to be between 6000-11,000 and the sodium sulfonate concentrations ranged from 0-18.4meq/100g polymer. Elemental analyses, however, indicated much higher molecular weights, which suggested that there was a distribution of chains with one, two, or no FY endgroups. The polymers were semicrystalline and melted at ca. 140℃ to form nematic mesophases that were stable over a temperature range of ca. 80℃. They were thermally stable to about 350℃. The ionomeric nature of the polymers was confirmed by the presence of intermolecular associations in nonpolar solvents, as demonstrated by dilute solution viscosity measurements.

The synthesis of new chiral smectic A (SA) side-chain liquid crystalline polysiloxanes (LCPs) and ionomers (LCIs) containing 4-allyloxy-benzoyl-4-(S-2-ethylhexanoyl) p-benzenediol bisate (ABB) as mesogenic units and 4-[[4-(2-propenyloxy)phenyl]azo]benzenesulfonic acid (AABS) as nonmesogenic units is presented. The chemical structures of the monomers and polymers are confirmed by FTIR spectroscopy or 1H-NMR. Differential scanning calorimetry (DSC), optical polarizing microscopy, and X-ray diffraction measurements reveal that all the polymers PI-PIV and ionomers PV-PVI exhibit SA texture. The results seem to demonstrate that the tendency toward the SA-phase region increases with increasing sulfonic acid concentration, and the thermal stability of the SA phase is determined by the flexibility of the polymer backbones and the interactions of sulfonic acid groups.

A new series of network liquid crystal polymers were synthesized by graft copolymerization of the difunctional mesogenic monomer 4-allyloxy-benzoyloxy-4'-allyloxybiphenyl (M) upon polymethylhydrosiloxane (PMHS). MonomerMacted not only as a mesogenic unit but also as a crosslinker for the network polymers. The chemical structures of the polymers were confirmed by IR spectroscopy. DSC, TGA, and X-ray scattering were used to measure their thermal properties and mesogenic properties. The glass transition temperature (Tg) of these network liquid crystal polymers was increased when the monomer was increased, and Td (temperature of 5%weight loss) at first went up and reached a maximumat P1, then went down. The slightly crosslinked polymers (P0, P1) show rubber-like elasticity, so it was called liquid-crystal elastomer. Network polymers will lose elasticity property with a highly crosslinked degree, and turn into thermosetting polymers (P4, P5). All polymers exhibited a smectic texture by X-ray scattering.

The synthesis of the two monomers M1 and M2 and a series of new side-chain cholesteric liquid crystalline elastomers P2-P8 is presented. The chemical structures of the monomers and elastomers obtained were confirmed by FTIR or 1H NMR spectroscopy. The cross-link density of the elastomers was determined by swelling experiments. The mesomorphic properties were investigated by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), polarizing optical microscopy (POM), and X-ray diffraction (XRD) measurements. Monomer M1 showed a cholesteric phase, and M2 revealed smectic and nematic phases. The effect of the cross-link density on the phase behavior of P2-P8 is discussed. Elastomers P2-P6 containing less than 12mol % of the cross-linking units displayed elasticity, reversible liquid crystalline phase transition, wide mesophase temperature ranges, and high thermal stability. Elastomer P7 displayed stress-induced birefringence, and P8 showed only elasticity with no other texture. Experimental results demonstrated that the glass transition temperatures increased, and the isotropization temperatures and the mesophase temperature ranges of P2-P6 decreased with increasing cross-link density.