Six kinds of polyurethane homopolymers and random copolymers were prepared with varying combinations of diols and diisocyanates by solution polymerization. For diol components, bishydroxyhexoxybiphenyl (BHHBP) was used as aromatic diol and hexanediol as aliphatic diol. Toluene 2,4-diisocyanate(TDI) and o-tolidine diisocyanate(TODI) were used for aromatic diisocyanate components. The thermal properties and mesomorphic behaviour were studied by using differential scanning calorimeter and polarizing optical microscope. The polyurethane prepared from BHHBP and TDI gave multiple endotherms in DSC thermograms but, contrary to the reported liquid crystallinity of the polymer, any mesomorphic texture was not observed. The temperature and frequency sweep were made to obtain information on rheological properties of the polymer using rheometrics dynamic spectrometer. The observed rheological behaviour confirmed the absence of liquid crystallinity. The measured viscoelastic parameters such as storage modulus(G') and loss modulus(G") were interpreted in view of Han and Jhon's theory. The polyurethane synthesized from hexanediol and TODI formed liquid crystalline structure, which was manifested by stir-opalescence observed through polarizing optical microscope. The typical liquid crystalline behaviour was also observed in the subsequent viscoelastic measurement : yield behaviour, relatively long relaxation time and shear thinning at low frequency range. The other polyurethane copolymers did not show clear mesomorphism. The crystal melting temperatures of the polyurethane random copolymers exhibited a eutectic point which is in relatively good agreement with the theoretical prediction of Flory. It was found that the copolymerization with monomers markedly different in chemical structure not only disrupts the structural regularity of the crystal but hinders the mesophase formation."
여섯 종류의 폴리우레탄 단독중합체와 random 공중합체를 방향성 diisocyanates 와 diol 단량체를 이용하여 용액중합법으로 합성하였다. 방향성 diol 성분으로는 bishydroxyhexoxybiphenyl(BHHBP) 이 alphatic diol 로서 는 1,6 hexanediol 이 사용되었고 TDI 와 TODI 가 방향성 diisocyanate 모노머로 사용되었다. 열적특성과 액정거동은 DSC 와 편광현미경을 사용하여 분석하였다. BHHBP 와 TDI 로부터 합성한 폴리우레탄은 DSC 주사결과 여러개의 흡열곡선을 보였으나 편광현미경에서는 액정상이 관찰되지 않았다. 폴리우레탄의 유변학적 특성을 조사하기위해 RDS 를 이용하여 온도와 주파수 sweep을 했으며 측정된 저장탄성률과 손실탄성률값들을 Han과 Jhon의 이론을 적용하여 해석하였다. TODI와 hexanediol을 이용하여 합성한 폴리우레탄은 액정상을 형성하였으며 편광현미경에서도 독특한 액정 texture가 관찰되었다. 항복거동, 긴 완화시간, 저주파수영역에서의 shear thinning등의 전형적인 액정의 점탄성 거동이 RDS 측정결과 관찰되었다. 다른 폴리우레탄 공중합체는 뚜렸한 액정상을 보이지 않았으며 결정용융거동의 경우 공융점이 중간조성에서 확인 되었고 Flory 식의 예상조성과 잘 일치하였다. 매우 다른 화학구조를 지니는 모노머를 이용하여 폴리우레탄공중합체를 합성하면 단독중합체가 지니는 결정의 질서도의 파괴는물론 액정상의 형성을 방해하는 것으로 나타났다.