Synthesis and properties of polyimides derived from isomeric biphenyltetracarboxylic dianhydrides (original) (raw)

2,2 H ,3,3 H -Biphenyltetracarboxylic dianhydride (i-BPDA) was suggested as a monomer for the synthesis of soluble polyimides with high thermal stability, and an efficient method of its preparation has been developed. Polyimides derived from i-BPDA and aromatic diamines (i.e. 4,4 H -oxydianiline, 2,2 H -bis(trifluoromethyl)benzidine and 9,9 H -fluorenylidene-4,4 H -dianiline) showed high glass transition T g Ͼ 330ЊC and degradation T d5 Ͼ 550ЊC temperatures, and were soluble in organic solvents (i.e. NMP, DMF, g-butyrolacton, CHCl 3 ), although their mechanical properties were inferior to those of polyimides composed of semirigid 3,3 H ,4,4 H -biphenyltetracarboxylic dianhydride (s-BPDA). Random copolymers, derived from i-BPDA and s-BPDA, retained superior mechanical properties of s-BPDA-based polyimides and showed improved solubilities, depending on the i-BPDA content. A regular increase of glass transition temperatures and a decrease of inherent viscosities of copolymers with increasing content of i-BPDA was observed, whereas the dielectric constants and degradation temperatures were found to be independent of the ratios of dianhydride units. ᭧