화학공학소재연구정보센터
홈 로그인 로그아웃 연락처 사이트맵
Polymer(Korea), Vol.32, No.3, 230-238, May, 2008
Export Citation
셀로비오스 옥타(콜레스테릴옥시카보닐)알카노에이트의 열 및 광학 특성
Thermal and Optical Properties of Cellobiose Octa(cholesteryloxycarbonyl)alkanoates
정승용, 마영대†
  • 단국대학교 고분자공학과
Seung Yong Jeong, and Yung Dae Ma†
  • Department of Polymer Science and Engineering, Dankook University, San 126, Jukjean-dong, Suji-gu, Yongin-si, Gyeongi-do 448-701, Korea
E-mail:
초록
셀로비오스 옥타(콜레스테릴옥시카보닐)알카노에이트(CCBn, n=2∼8,10, 스페이서중의 메틸렌 단위들의 수)의 열 및 광학 특성을 검토하였다. 모든 시료들은 좌측방향의 나선구조를 지닌 단방성 콜레스테릭 상들을 형성하였다. n=2 혹은 10인 CCBn은 3≤n≤8인 CCBn과 달리 콜레스테릭 상의 전 온도구간에서 반사색깔을 나타내지 않았다. 이러한 사실은 콜레스테릴 그룹에 의한 나선의 비틀림력은 콜레스테릴 그룹과 셀로비오스 사슬을 연결하는 스페이서의 길이에 민감하게 의존함을 시사한다. 액체 상에서 콜레스테릭 상으로의 전이온도(Tic)와 유리전이온도는 n이 증가함에 따라 낮아지며 홀수-짝수 효과를 나타내지 않았다. Tic에서의 전이엔트로피는 n이 2에서 6까지 증가하나 n=7에서 급격히 감소한 후 재차 n이 8에서 10으로 증가함에 따라 증가하였다. n=7에서 급격한 변화는 곁사슬 그룹들의 배열의 차이에 의해 초래되는 것으로 생각된다. CCBn에서 관찰되는 액정 상의 열적 안정성과 질서도 그리고 광학피치의 온도의존성은 셀룰로오스 트리(콜레스테릴옥시카보닐)알카노에이트들 그리고 글루코오스 펜타(콜레스테릴옥시카보닐)알카노에이트들에 대해 보고된 결과들과 현저히 달랐다. 이들의 결과를 중합도, 글루코오스 몰 단위당의 메조겐 단위들의 수 그리고 분자들의 입체형태의 차이들의 견지에서 검토하였다.
The thermal and optical properties of cellobiose octa(cholestryloxycarbonyl)alkanoates (CCBn, n=2∼8,10, the number of methylene units in the spacer) were investigated. All the samples formed monotropic cholesteric phases with left-handed helical structures. CCBn with n=2 or 10, in contrast with CCBn with 3≤n≤8, did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer connecting the cholesteryl group to the cellobiose chain. The isotropic-cholestropic transition (Tic) and glass transition temperatures decreased with increasing n and showed no odd-even effect. The transition entropy at Tic increased with increasing n from 2 up 6, but at n=7 it drops significantly and then increased again with increasing n from 8 to 10. The sharp change at n=7 may be attributed to a difference in arrangement of the side groups. The thermal stability and degree of order in the mesophase and the temperature dependence of the optical pitch observed for CCBn were significantly different from those reported for the cellulose tri(cholesteryloxycarbonyl)alkanoates and glucose penta(cholesteryloxycarbonyl)alkanoates. The results were discussed in terms of the differences in the degree of polymerization, the number of the mesogenic units per mole-glucose unit, and the conformation of the molecules.
Keywords:cellobiose;cholesterol;spacer length;cholesteric phase;optical pitch
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