N,N'-[2,2′-bis(trifluoromethyl)-4,4′-biphenylene]bis(4-aminobenzamide) (TFAB) was synthesized from 4-nitrobenzoyl chloride and 2,2′-bis(trifluoromethyl)benzidine (TFB). The obtained TFAB, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and 4,4′-biphthalic anhydride (BPA) were used to synthesize polyimide copolymers (Co-PIs) containing amide groups. Flexible and tough Co-PI films were prepared from poly(amic acid) (PAA) through solution-casting using chemical and thermal imidization methods. The thermomechanical properties and optical transparency of the Co-PI films with various BPA monomer contents were investigated. The coefficients of thermal expansions (CTEs) of the Co-PI films were improved linearly with increasing BPA content. However, their optical transparency was found to worsen with increasing BPA content.

4-nitrobenzoyl chloride와 2,2'-bis(trifluoromethyl)benzidine(TFB)를 이용하여 N,N'-[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]bis(4-aminobenzamide)(TFAB)의 아민 단량체를 합성하였다. 합성된 TFAB와 무수물 단량체인 4,4'-(hexafluoro-isopropylidene) diphthalic anhydride(6FDA) 및 4,4'-biphthalic anhydride(BPA)를 다양한 몰 비로 반응하여 폴리아믹산(polyamic acid, PAA)을 합성한 후 화학적-열적 이미드화 반응을 거쳐 아미드 그룹을 가지는 폴리이미드 공중합체(Co-PI)를 합성하였다. 용액 캐스팅으로 합성된 Co-PI 필름은 유연하고 질긴 성질을 보였다. 합성된 Co-PI는 BPA의 함량 변화에 따라 열적-기계적 성질 및 광학 투명도 등을 조사하였다. Co-PI 필름의 열 팽창 계수(coefficient of thermal expansion, CTE) 값은 BPA의 몰 비가 증가할수록 감소하였지만, 광학 투명성에서는 반대의 결과를 보여주었다.

Keywords: copoly(amide imide); colorless and transparent polyimide; thermo-mechanical properties; optical transparency