As part of our continuing effort to establish the structure-morphology-property relationship for high Tg azopolymides, a new diamine (azoBPAA) containing two azobenzenes was synthesized via a four-step route. It was polymerized with five commercial dianhydrides: pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), oxy-4,4'-di(phthalic anhydride) (ODPA), and 1,1,1,3,3,3-hexafluoro-2,2-bis(4-phthalic anhydrido)-propane (6FDA) to afford a series of amorphous, heat-resistant (Tg ranging from 276-307 �C) linear homopolyimides containing two azobenzenes/repeat unit. In addition to homopolyimides, four copolyimides were also prepared from 6FDA, azoBPAA and 1,3-bis(3-aminophenoxy)benzene (APB). These polymers displayed high thermo-oxidative and thermal stabilities with 5wt% weight-loss temperatures between 451-498 �C in air and 420-456 �C in nitrogen, respectively. The photo-directed bending of cantilevers composed of these materials was examined upon exposure to linearly polarized 445nm light. The photomechanical response of homopolyimides increased from 13� for azoBPAA-PMDA to 84� for azoBPAA-OPDA in parallel with the increasing flexibility of dianhydrides. As expected, the bending angles increased with the contents of azoBPAA for 6FDA-based copolyimides albeit bidirectional bending was observed below 45mol% of AzoBPAA content, and only unidirectional bending was observed thereafter. WAXD results indicated that all the polyimides were amorphous except PMDA and BPDA-based homopolyimides, which contain various degrees of crystallinity.

Photomechanical responses of high Tg, main-chain-azobenzene-containing polyimides

246th National Meeting (2013)

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