A new series of thermotropic polyurethanes was synthesized by reacting para- and meta-type diisocyanate monomers of 2,6-tolylene diisocyanate (2,6-TDI), 2,5-tolylene diisocyanate (2,5-TDI), 2,4-tolylene diisocyanate (2,4-TDI), and 1,4-phenylene diisocyanate (1,4-PDI) with 4,4'-Bis(10-hydroxydecyloxy)biphenyl (BP10: HOC10H20OC6H4C6H4OC10H20OH) in DMF. The influence of substituents on the thermal behavior of the polyurethanes was compared to the parent diisocyanates. Characterizations of the monomers and polyurethanes were performed with infrared and (1)H NMR spectra. The phase transition behaviors of polyurethanes were investigated with DSC and polarized microscopy (POM). Our result showed that the monomers of 4,4'-Bis(10-hydroxydecoxy)biphenyl exhibited a smectic type mesophase. The polyurethane, 2,4-TDI/BP10 with a methyl substituent in the phenylene unit, was monotropically nematic. In contrast, 1,4-PDI/BP10 without a methyl substituent in the phenylene unit exhibited no explicit mesomorphic behavior, whichwas confirmed by the DSC and polarizing microscopy experiments.

액정성을 나타내는 단량체 4,4'-bis(10-hydroxydecyloxy)biphenyl (BP10: HOC10H20OC6H4C6H4OC10H20OH)을 합성하여 파라와 메타형의 diisocyanate 즉 2,6-tolyene diisocyanate (2,6-TDI), 2,5-tolylene diisocyanate (2,5-TDI), 2,4-tolylene diisocyanate (2.4-TDI), 1,4-phenylene diisocyanate (1,4-PDI)를 DMF 용매에 용해시켜 반응시킴으로써 새로운 형태의 폴리우레탄을 합성하였다. 생성된 폴리우레탄의 구조는 (1)H NMR과 IR 스펙트럼에 의해 확인하였고 열적성질은 DSC와 편광현미경으로 관찰하였다. 단량체 BP10은 스멕틱상을 형성하였으며 메틸 치환기를 가진 폴리우레탄 2,4-TDI/BP10에서는 냉각시 단방성 액정으로만 관찰되었다. 그러나 메틸 치환기를 가지고 있지 않는 폴리우레탄 1,4-PDI/BP10에서는 DSC 및 편광현미경 실험에서도 액정상을 전혀 관찰할 수 없었다.