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Synthesis and Characterization of Polymers with Azobenzene and Hexamethylene Groups in Main Chain

주사슬에 아조벤젠기와 헥사메틸렌기를 갖는 고분자의 합성 및 특성

  • Gu, Su-Jin (Division of Advanced Materials Science and Engineering, Kongju National University) ;
  • Lee, Eung-Jae (Department of Bioenvironmental & Chemical Engineering, Chosun College of Science & Technology) ;
  • Bang, Moon-Soo (Division of Advanced Materials Science and Engineering, Kongju National University)
  • 구수진 (공주대학교 신소재공학부) ;
  • 이응재 (조선이공대학교 생명환경화공과) ;
  • 방문수 (공주대학교 신소재공학부)
  • Received : 2019.01.21
  • Accepted : 2019.04.05
  • Published : 2019.04.30

Abstract

Polymers with various compositions of azobenzene and hexamethylene groups in the main chain were synthesized by a Schotten-Baumann reaction and their properties were investigated. The chemical structures and physical properties of the synthesized polymers were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and x-ray diffraction. The polymers showed an inherent viscosity of 1.28-1.36 dl/g and were relatively insoluble in most organic solvents. The melt transition temperature increased rapidly with increasing number of azobenzene groups in the polymer. When the azobenzene monomer content was more than 50 mol%, no melting transition occurred below the decomposition temperature. Among the polymers with a melt transition temperature, the MP-A3C7 and MP-A5C5 polymers were liquid crystalline materials and exhibited a nematic phase with weak liquid crystallinity over a wide liquid crystal temperature range. This difference in the properties of the synthesized polymers is likely due to the changes in intermolecular forces resulting from the linearity and polarity of the trans-form of azobenzene.

주 사슬에 다양한 조성의 아조벤젠기와 헥사메틸렌기를 갖는 고분자들을 쇼텐-바우만 반응을 이용하여 합성하고, 이들의 물성을 조사하였다. 합성된 고분자들의 화학 구조와 물리적 성질은 푸리에 적외선 분광법 (FT-IR), 핵자기공명 분광법($^1H-NMR$), 시차주사 열량 분석법(DSC), 열 중량 분석법(TGA), 편광 현미경법(POM), X-선 회절법(XRD)으로 조사되었다. 합성된 고분자들은 1.28에서 1.36 dL/g의 고유 점성도를 갖는 비교적 높은 분자량의 고분자들이 합성되었으며, 용해도 조사에 사용된 대부분의 용매에 잘 용해되지 않았다. 고분자 내의 아조벤젠기의 함량이 증가함에 따라 용융 전이온도($T_m$)가 급격히 높아졌으며, 아조벤젠 단위체의 함량이 50 mol% 이상인 경우 분해온도 이하에서 상 전이는 일어나지 않았다. 합성된 고분자들 중, MP-A3와 MP-A5는 넓은 액정 온도구간을 갖는 액정 고분자였으며, 약한 액정성을 갖는 네마틱 상을 나타냈다. 합성 고분자들의 이러한 성질의 차이는 trans 형태인 아조벤젠기의 선형성과 극성에서 비롯된 분자간력의 변화에 기인하는 것으로 판단된다.

Keywords

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Fig. 1. Synthesis routes of DHAB.

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Fig. 2. Scheme for polymerization.

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Fig. 3. 1H-NMR spectrum of DHAB. (CF3COOD-d)

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Fig. 4. FT-IR spectra of polymers. (KBr)

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Fig. 5. DSC thermograms of polymers.

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Fig. 6. TGA thermograms of polymers.

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Fig. 7. Cross-polarized optical micrographs of polymers(magnification of x50).

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Fig. 8. X-ray diffractograms of polymers.

Table 1. Composition of Monomers for Polymers

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Table 2. Inherent Viscosity and Solubility Tests of Polymers

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Table 3. DSC and TGA Data of Polymers

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