Moon-Soo Bang

Synthesis and Properties of Polybenzoxazole Precursors having Oligo(oxy ethylene) pendant

Abstract Poly(o-hydroxyamides)(PHAs) copolymers having oligo(oxy ethylene) pendant in the main chain were synthesized by solution polycondensation reaction at low temperature. Copolymer precursors were studied by fourier transform infrared(FT-IR), differential scanning calorimeter(DSC), thermogravimetric analyzer(TGA), universal testing machine(UTM) and limited oxygen index(LOI). The inherent viscosities of the PHAs measured at 35℃ in DMAc or DMAc/LiCl solution were in the range of 0.74∼1.42 dL/g. Solubility of the precursors with higher oligo(oxy ethylene) unit was increased, but the PBOs were nearly insoluble in a variety of solvents. The degradation temperature of the copolymer precursors was recorded in the ranges of 408∼664℃ in nitrogen and char yields showed 13∼59% values at 900℃. The mechanical properties and flame retardancy of copolymer precursors decreased with higher oligo(oxy ethylene) unit. Key Words : Polybenzoxazoles, Poly(o-hydroxyamide)s, Thermal cyclization reaction *

Synthesis and Properties of Liquid Crystalline Copolymers with Ether-ether-ester Linkage in Main Chain

Abstract Copoly(ether-ether-ester)s having flexible side chain were synthesized by polycondensation. Intrinsic viscosities of polymers were between 0.42 and 0.78dl/g in tetrachloroethane. The polymer structures were investigated by 1 H-NMR and FT-IR, and thermal and liquid crystalline properties of polymers were measured by DSC, TGA, POM and XRD. As results of investigations, synthetic copolymers exhibited lower melting temperature than homopolymers. When the biphenylene units contents in copolymer were more than 60 mol %, nematic mesophase was observed, and the mesophase of synthetic polymers was dependent upon biphenylene content. Key Words : Liquid Crystal, Mesophase, Aromatic Copolymer, Biphenylene, Ether-Ether-Ester 본 논문은 공주대학교 자체학술연구비로 수행되었음. * 교신저자 : 방문수 (msbang@kongju.ac.kr)접수일 10년 03월 02일 수정일 10년 04월 02일 게재확정일 10년 04월 09일 1. 서론 열적으로나 화학적으로 안정한 고분자재료의 개발을 위하여 수많은 연구결과들이 보고되고 있다. 특히 주사슬이 전방향족구조로 되어있는 고분자들은 기계적, 열적성질이 우수한 반면에 가공성에 많은 문제점을 가지고 있다. 이를 해결하기 위한 방법으로 전방향족고분자의 구조를 변형하여 용융가공이 가능하며, 우수한 가공특성을 갖도록 열방성액정중합체(Thermotropic Liquid Crystalline Polymer (TLCP))를 합성하는 것이다[1-3]. 지금까지 수많은 액정중합체들이 합성되었고, 액정형성에 관한 이론들이 정립되어 액정중합체 합성에 활용되어 오고 있다. 중합체가 액정상을 형성하기 위해서는 분자 중에 메소겐을 포함하여야 하며, TLCP의 경우 고분자사슬의 축비가 3이상이면 액정상을 형성할 수 있음이 알려져 있다[4-6]. 따라서, 사슬 중 짧은 강직구조를 갖는 비액정중합체에 프탈산, 비페놀. 하이드록시 벤조산과 같은 방향족화합물을 일정비율 첨가하여 메소겐이 형성되도록 공중합체를 설계한다면 비액정중합체에 액정성을 부여할 수 있으며, 그 결과, 중합체의 가공성을 개선할 수 있고 물성도 향상시킬 수 있을 것이다[7]. 본 연구자[8]에 의하여 연구된, 길이가 다른 알콕시 곁사슬을 갖으며, 전방향족 구조를 갖는 아래 구조의 두 중합체 시리즈 중에서 주사슬에 페닐렌기가 ether-ether-ester 기로

Effect of Aromatic Ring Content on the Properties of Liquid Crystalline Copolyesters

The liquid crystalline copolymers were synthesized through direct polycondensation using 4-[4-(4-hydroxyphenoxy)butoxy]benzoic acid (HBBA) and p-hydroxy benzoic acid (HBA) as monomers. The structure and properties for synthesized copolymers were investigated by H-NMR, FT-IR, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA) and polarizing optical microscope (POM). As result of investigations, inherent viscosities (ηinh) of polymers were measured as 0.77~1.60 dL/g in phenol/p-chlorophenol /1,1,2,2-tetrachloroethane (25/40/35=w/w/w). Except for P-80, the ranges of the transition and mesophase temperature of copolymers were increased with increasing the amount of HBA. These properties of polymers were presumably due to increasing of the irregularity and rigidity of polymer chains.

Study on the Isothermal Crystallization Behaviors of PEN/TLCP Blends

Abstract: The isothermal crystallization behaviors of blends of poly(ethylene naphthalate) (PEN) and a thermotropic liquidcrystalline polymer (TLCP) were investigated by differential scanning calorimetry (DSC) as functions of crystallization tem-perature and blend composition. Avrami analyses were applied to obtain information on the crystal growth geometry andthe factors controlling the rate of crystallization. The crystallization kinetics of the PEN/TLCP blends followed the Avramiequation up to a high degree of crystallization, regardless of crystallization temperature. The calculated Avrami exponentsfor PEN/TLCP revealed three-dimensional growth of the crystalline region in each blend. The crystallization rate of eachblend increased as the crystallization temperature decreased, and decreased as the TLCP content increased. The crystalli-zation of PEN in the blend was affected by the addition of TLCP, which acts as a nucleating agent.Keywords: Avrami equation, isothermal crystallization kinetics, nucleating agent, PEN/TLCP blend

Synthesis and Properties of Semi-flexible Liquid Crystalline Polyesters with Rigid Lateral Group

Jong-Ryul Park, Eung-Jae Lee, Doo-Soo Yoon, Moon-Soo Bang and Jae-Kon Choi Division of Advanced Materials Science and Engineering, Kongju National University, Cheonan 330-717, Korea Dept. of Bioenvironmental & Chemical Engineering, Chosun College University of Science & Technology, Gwangju 501-744, Korea Dept. of Biochemical & Polymer Engineering, Chosun University, Gwangju 501-759, Korea (Received November 6, 2013, Revised November 13, 2013, Accepted November 18, 2013)