SYNTHESIS OF SIDE-CHAIN LIQUID-CRYSTAL POLYMERS BY LIVING RING-OPENING METATHESIS POLYMERIZATION .5. INFLUENCE OF A MESOGENIC GROUP AND AN INTERCONNECTING GROUP ON THE THERMOTROPIC BEHAVIOR OF THE RESULTING POLYMERS

Norbornene derivatives containing ((4'-cyano-4-biphenyl)yl)oxy mesogens linked to the norbornene through methylene groups (n = 3-7, 9-12) and an ester were polymerized by Mo(CHR)(NAr)-(O-t-Bu)2 (Ar = 2,6-C6H3-i-Pr2, R = t-Bu) in a living manner. Polymers in which n = 3 were amorphous, whereas all other polymers (n = 4-7,9-12) displayed enantiotropic nematic mesophases that were independent of the molecular weight. Polymers having 9-12 methylene spacers did not undergo side chain crystallization and did not show an odd-even effect, in contrast to analogous polymers containing ((4'-methoxy-4-biphenyl)yl)oxy mesogens, which exhibited side chain crystallization when n > 8 and an odd-even effect when n < 7. The lower tendency to form a more ordered phase and the absence of an odd-even effect are attributed todipole-dipole repulsions between ((4'-cyano-4-biphenyl)yl)oxymesogens. Polymers containing ((4'-methoxy-4-biphenyl)yl)oxy mesogens attached through ether linkages gave highly crystalline SCLPCs, even with relatively few methylene units in the spacer (n = 4-6).