CP2 is a high-Tg polyimide that was developed in 1980's from the NASA-Langley Research Center �Colorless Polyimides� R&D program toward space applications, where high optical transparency in 300-600nm region was an important requirement. Recently, we have shown that CP2 is promising as a high-temperature shape memory (SM) polymer, and when incorporated with a tris(azobenzene-amine) crosslinker, a CP2 cantilever, upon exposure to a polarized blue light at room temperature, can be rendered photomechanically active as well. However, it was puzzling that when an �uncrosslinked� CP2 film was immersed in a heat-bath at temperatures above its Tg (~199 oC), it could be easily stretched, bend or twisted, and the temporary shape could be fixed by cooling under a constant stress. When returned to the heat-bath without being under stress, the CP2 film would fully recover its original shape. This SM effect could be repeated (>10 times) and was observed also in CP2-polymers crosslinked with a tris(phenylamine) compound. Interestingly, such SM effect was not observed in other similarly prepared (without crosslinker added) polyimide films (e.g. CP1 and Ultem). Thus, in this work, we have attempted to delineate the source and mechanism of crosslinking, and correlate the crosslinking chemistry and the SM effect apparently unique to CP2.

Chemical origin of shape-memory effect in CP2 polyimide

246th National Meeting (2013)

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