Polyimide molecular composites containing a stiff‐chain polymer derived from 1,5‐diaminonaphathalene and pyromellitic dianhydride

Abstract

AbstractPolyimide molecular composite (MC) films were prepared by embedding a stiff‐chain polyimide (PIS) in the ductile matrix of a flexible‐chain polyimide (PIF) by blending their respective poly(amic acid) precursor solutions, followed by casting, drying, and thermal imidization upto 300°C. The PIS was prepared from pyromellitic dianhydride (PMDA) and 1,5‐diaminonaphathalene (DAN), whereas the PIF was prepared from the same dianhydride and 4,4′‐oxydianiline (ODA). Transparent, tough, and creasable MC films were obtained with 2.5–40 wt% of PIS content. The disruption of crystalline order of PIS in the MC films evidenced its fine dispersion in the matrix. Visco‐elastic measurements showed a single and enhanced value of the glass transition temperature for MC films indicating miscibility of this polyimide pair. Furthermore, the variation of charge transfer (CT) fluorescence intensity with the PIS content in the blends verified complete miscibility upto 30 wt% of PIS loading. These MCs showed a notable enhancement in the mechanical properties. Among all, the blend containing 30 wt% of stiff‐chain molecules gave the best combination of properties when compared with the matrix polyimide: a 50% higher value of tensile modulus, a 17°C rise in the glass transition temperature, and better thermal stability. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers