Preparation of Porous Structure from ABA-type Triblock Copolymers Derived from 6FDA-TeMPD Polyimide Macroinitiators

A fluorine-containing polyimide macroinitiator was synthesized from 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,3,5,6-tetramethyl-1,4-phenytene diamine (TeMPD). An ABA-type triblock copolymer having both thermally stable polyimide blocks and thermally labile poly (methyl methacrylate) blocks was prepared from the 6FDA-TeMPD macroinitiator by atom transfer radical polymerization. The thermal properties of the macroinitiator and the triblock copolymer were examined by several types of analyses, including thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The macroinitiator showed high glass transition temperature (T(g): 391 degrees C) and high thermal decomposition temperature (more than 500 degrees C in nitrogen). On the other hand, the triblock copolymer film showed phase separation morphology supported by DMA data. The nanoporous structure with pore sizes in the range of 50-100 nm could be prepared by heating the triblock copolymer film to induce the thermal degradation of the PMMA block at 300 degrees C for 12 hours. A low dielectric constant of 2.36 was obtained for the nanoporous film.