Phase transition behaviors and physical properties of thermotropic poly(ester-imide)s with various molecular structures = 다양한 분자 구조의 열방성 에스테르이미드 중합체들의 상전이 거동과 물리적 성질에 관한 연구

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Various thermotropic liquid crystalline poly(ester-imide)s were synthesized from asymmetric N-(ω-carboxyalkylene) trimellitic imide and hydroquinone diacetate or methylhydroquinone diacetate. Their phase transition behaviors were investigated with the particular emphasis on the monotropic liquid crystalline behaviors. Poly(ester-imide)s with or without methylene side pendant group were synthesized from N-(ω-carboxyalkylene) trimellitic imide containing 4 and 6 methylene units. The polymers without methylene side group showed typical enantiotropic mesophase transition behaviors, which show melting transition and mesophase to isotropic phase transition during heating. But those without side group exhibit no crystallization during conventional cooling process - so called ````amorphous type mesophase transition,```` Their crystallization was extremely slow that approximately 32 hrs of annealing was necessary to complete in the fastest cases. The mesophases of all polymers are verified as nematic phase from the distinct peak shapes of elastic moduli and viscosities during temperature scan. Time-temperature superposition was tested for a amorphous thermotropic liquid crystalline polymer. The superposition holds for both isotropic and nematic phases but failed in biphase. A poly(ester-imide) containing 10 methylene units and methyl side pendant group was synthesized. On DSC cooling scans a exothermic process, which showed little dependence on the scan rate than other exotherms, was found. The morphology evolution showed the clear difference at the boundary of the exotherm. When cooled below the exothermic transition, tread-like morphology appeared on polarized light microscopy. Whereas, spherulic texture was observed above the transition. The monotropic mesophase transition was confirmed by the rheological temperature sweep measurements. The elastic moduli and complex viscosity exhibited unique hysteresis shape in cooling and subsequent heating scan. The mesophase w...
Chung, In-Jae정인재
한국과학기술원 : 화학공학과,
Issue Date
157716/325007 / 000965064

학위논문(박사) - 한국과학기술원 : 화학공학과, 2000.2, [ xiii, [145] p. ]


Phase transition; Poly(ester-imide); Liquid crystalline polymer; Rheological properties; 유변학적 성질; 상전이; 에스테르이미드 중합체; 액정고분자

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