Applied Chemistry for Engineering (공업화학)

The Korean Society of Industrial and Engineering Chemistry (한국공업화학회)
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Synthesis and Properties of Di-azomesogenic Liquid Crystal Compounds with Terminal Substituents

말단에 치환기를 갖는 이-아조메소젠 액정화합물의 합성 및 성질

  • Park, Jong-Ryul (Division of Advanced Materials Science and Engineering, Kongju National University) ;
  • Gu, Su-Jin (Division of Advanced Materials Science and Engineering, Kongju National University) ;
  • Yoon, Doo-Soo (Dept. of Bioenvironmental & Chemical Engineering, Chosun College of Science & Technology) ;
  • Bang, Moon-Soo (Division of Advanced Materials Science and Engineering, Kongju National University) ;
  • Choi, Jae-Kon (Dept. of Biochemical & Polymer Engineering, Chosun University)
  • 박종률 (공주대학교 신소재공학부) ;
  • 구수진 (공주대학교 신소재공학부) ;
  • 윤두수 (조선이공대학교 생명환경화공과) ;
  • 방문수 (공주대학교 신소재공학부) ;
  • 최재곤 (조선대학교 생명화학고분자공학과)
  • Received : 2015.09.09
  • Accepted : 2015.11.02
  • Published : 2015.12.10
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Abstract

Two series of symmetric dimesogenic compounds containing a butylene or 1-methylbutylene spacer as a flexible group were synthesized. The mesogenic groups of synthesized compounds consist of an azobenzene group with a terminal substituent. Chemical structures as well as, thermal, mesomorphic, and photochemical properties of the synthesized compounds were investigated using FT-IR, $^1H-NMR$, differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and UV-visible spectrometry. P-H, P-F, and $P-OC_6H_{13}$ showed monotropic liquid crystal phases, whereas the others showed enantiotropic liquid crystal phases. Compounds with butylene group as a flexible spacer exhibited wider mesophase temperature ranges and higher thermal transition temperatures than compounds containing a 1-methylbutylene group. Compounds with a high absolute value of the Hammett substituent constant exhibited high thermal transition temperatures and improved stability in the liquid crystal phase. Furthermore, in the absence or presence of UV light illumination, terminal substituents of the azomesogenic group were important factors in deciding the maximum absorbance wavelength (${\lambda}_{max}$) and the rate of photoisomerization (K).

유연격자로써 부틸렌 또는 1-메틸부틸렌기를 갖는 두 시리즈의 대칭성 이메소젠 액정 화합물을 합성하였으며, 이 화합물들의 메소젠 그룹은 말단에 치환기를 포함하고 있는 아조벤젠기로 되어 있다. 합성된 화합물의 화학구조와 열적 성질, 액정성 및 광화학 성질은 FT-IR, $^1H-NMR$, 시차주사열량측정(DSC), 편광현미경(POM), 그리고 UV-visible 분광분석법에 의하여 조사되었다. 화합물 P-H, P-F, $P-OC_6H_{13}$는 단방성 액정성을, 나머지 화합물들은 양방성 액정성을 나타내었고, 유연격자로써 부틸렌기를 갖는 화합물이 1-메틸부틸렌기를 갖는 화합물들보다 넓은 액정상 온도구간과 높은 열전이온도를 나타내었으며, Hammett 치환기 상수의 절댓값이 큰 화합물이 높은 열전이 온도와 액정안정성을 나타내었다. 또한, UV 광 조사 시, 아조 메소젠 그룹의 말단 치환기가 최대흡수파장(${\lambda}_{max}$) 및 광이성화 속도(K)를 결정하는 중요한 요인임을 알 수 있다.

Keywords

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