SYNTHESIS OF FUNCTIONALIZED SIDE-CHAIN LIQUID-CRYSTAL POLYMERS - POLYPHENOLIC COMBS

This work studied the synthesis of self-ordering comb polymers contain ing functionalized side chains. The target polymers in the study had m ethacrylate backbones with hydroxy-functionalized side chains containi ng phenolic groups at their termini. The synthesis of the targeted pol ymers was accomplished in seven steps and involved identifying suitabl e protecting groups for the phenolic monomers before free-radical poly merization. The various protecting groups explored for this purpose we re dimethylthexylsilyl ether (OSIGMA), benzyl carbonate (OCOOBn), trim ethylsilyl ether (OTMS), triethylsilyl ether (OTES), diphenylmethylsil yl ether (ODPMS), and tetrahydropyranyl ether (OTHP) groups. Our studi es show that ODPMS and OTHP ether groups are best suited to synthesize the functionalized polymers. Deprotection of polymers protected with these groups after free-radical polymerization could be quantitatively accomplished under relatively mild conditions. One of the target poly mers and its corresponding functionalized monomer were found to melt i nto liquid crystalline fluids which exhibited isotropization transitio ns at higher temperatures. The synthesis of these polymers is signific ant in the context that mesomorphic behavior is not considered common in organic molecules with functions that can form intermolecular hydro gen bonds. Also these comb polymers may exhibit interesting behavior a t interfaces with solid surfaces given the presence of reactive or hyd rogen-bond-forming functions in their self-assembling side chains. One example would be their behavior as coupling agents at a composite mat erial interface.