Crystalline Homopolyimides and Copolyimides Derived from 3,3′,4,4′-Biphenyltetracarboxylic Dianhydride/1,3-Bis(4-aminophenoxy)benzene/1,12-Dodecanediamine. 1. Materials, Preparation, and Characterization

Crystalline homopolyimides are shown to occur by DSC from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and either 1,3-bis(4-aminophenoxy)benzene (134APB) or 1,12-dodecanediamine (C12). Additionally, copolyimides synthesized from these monomers are crystalline in all compositions studied. Each composition was found to have a singular glass transition temperature, which is rectilinearly dependent on the percent of 134APB/C12. A similar relationship is found for the crystallization temperature but not for the apparent melting temperature. Upon heating, a triple-melting behavior was observed when materials were crystallized at large degrees of supercooling. Otherwise, a conventional double-melting behavior was seen. The equilibrium melting temperature (Tm°) was estimated using the Hoffman-Weeks method. Results indicate that compositions with 134APB composition >40% are dominated by the 134APB/BPDA polyimide phase, and below it by the C12/BPDA polyimide phase. The value of T_m° for the 134APB/BPDA polyimide is about 410 °C and for the C12/BPDA polyimide is about 243 °C.