Abstract
Miscibility of polymer blends prepared from poly(2,2(m-phenylene)-5,5'-ben-zimidazole), PBI, and aromatic polyimides(Pls) were investigated as a function of structural variations of polyimide component utilizing DSC and FTIR spectroscopy. Film and powder blend samples were prepared from the solution of PBI and PIs in N,N-dimethylacetamide(DMAc) and/or 1-methyl-2-pyrrolidinone(NMP). The miscibility of the PBI/PI blends was found to improve with increasing polarity of the polyimide component. For example, 3,3'-diaminodiphenyl sulfone(3,3'-DDS)/3,3',4,4'-benzophenone tetracarboxylic dianhydride(BTDA), 3,3'-DDS/4,4'-ox-ydiphthalic anhydride(ODPA) and 4,4'-isopropy lidene dianiline(BIS-A)/ODPA polyimide systems were miscible with PBI. However, when the polar polyimide components(C=O, O and SO ) were replaced by non-polar components such as hexafluoropropylidene group((CF ) C) miscibility was significantly reduced. Thus, immiscibility was obtained for polyimides based upon 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl) ethylidene] his-1,3-isobenzofuranedione (6FDA) such as 4,4'-di-aminodiphenyl sulfone(4,4'-DDS)/6FDA,4,4'-oxydianiline(4,4'-ODA)/6FDA and BIS-A/6FDA polyimide systems. Non-hydrogen bonded solubility parameters for the PBI and Pls were estimated using group molar attraction constants(F) and group molar volume(V). The observed miscibility behavior was in good accord with the prediction of miscibility by the non-hydrogen bonded solubility parameter approach.
