Polyamicacids using BTDA (3,3',4,4'-benzophenone tetracarboxylic dianhydride) with 2,4-TDA (2,4'-toluene diamine) and 4,4'-MDA (4,4'-methylene dianiline) were synthesized by condensation polymerization. Blend solutions of poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole](PBI) and the above synthesized polyamicacids were prepared by using a cosolvent, DMAc and cast film or precipitated into powder, then cured at higher temperatures than the estimated T_g's. Miscibility and the specific interactions responsible for miscibility were investigated using DSC and FT-IR. Phase diagram was obtained by DSC and thermal stability of the blends was also stooled using TGA. Both the blend systems, PBI/BTDA+2,4'-TDA(blend Ⅰ ) and PBI/BTDA+4,4'-MDA(blend Ⅱ) are miscible ; evidences for miscibility were optically clear films and single composition dependent T_g's intermediate between those of the homopolymers. LCST type phase behavior was obtained by DSC annealing study and thermal stability was enhanced in these blend systems. From FT-IR studies, carbonyl stretching band of PIs and N-H stretching band of PBI shifted to lower frequencies about 7∼10cm^-1 and 50∼55cm^-1, respectively. Thus hydrogen bonding between carbonyl arised from 5-membered ring solely and N-H is responsible to bring a miscible system.

BTDA(3,3',4,4',-benzophenone tetracarboxylic anhydride)와 두 종류의 diamine인 2,4-TDA(2,4'-toluene diamine)과 4,4'-MDA(4,4' -methylene dianiline)를 용매 DMAc(di-methyl-acetamide)속에서 반응시켜 폴리아믹산(PAA)을 합성하였으며, 이들 두 종류의 PAA를 고내열성, 무정형 고분자인 poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole : PBI]와 각각 용액 블렌딩하여 PBI/PAA 분말 및 필름으로 제조한 후 각각 블렌드의 T_g보다 높은 온도에서 수분을 빼면서 경화시킨 PBI/PI 시료를 DSC (differential scanning calorimeter) 와 FT-IR (fourier transform-Infrared spectroscopy)를 사용하여 상용성과 상변이 현상 그리고 TGA로 열안정성을 조사하였다. 두 블렌드 시스템, PBI/BTDA+2,4'-TDA(blend I )와 PBI/BTDA+4,4'-MDA(blend Ⅱ)는 광학적으로 투명한 필름과, 전 블렌드조성에서 하나의 유리전이온도를 나타냄으로써 상응성을 가지고 있으며 어닐링 온도를 변화시키면서 측정한 T_g로부터의 상평형 그림은 전형적인 LCST 형의 상분리 현상을 보였다. 또한 FT-IR로 폴리이미드의 C=0와 PBI의 N-H그룹의 band가 낮은 주파수쪽으로 이동하는 현상으로루터 폴리이미드와 폴리벤지미다졸사이의 수소결합이 상용성을 가져다 주는 요인으로 사려된다.

Keywords: polybenzimidazole; aromatic polyimide; polymer blend; miscibility; hydrogen bonding