Smart materials, such as thin-film piezoelectric polymers, are interesting for potential applications on Gossamer spacecraft. This investigation aims to predict the performance and long-term stability of the piezoelectric properties of poly(vinylidene fluoride) (PVDF) and its copolymers under conditions simulating the low-Earth-orbit environment. To examine the effects of temperature on the piezoelectric properties of PVDF, poly(vinylidenefluoride-co-trifluoroethylene), and poly(vinylidenefluoride-co-hexafluoropropylene), the d(33) piezoelectric coefficients were measured up to 160 ° C, and the electric displacement/electric field (D-E) hysteresis loops were measured from -80 to +110 ° C. The room-temperature d(33) coefficient of PVDF homopolymer films, annealed at 50, 80, and 125 ° C, dropped rapidly within a few days of thermal exposure and then remained unchanged. In contrast, the TrFE copolymer exhibited greater thermal stability than the homopolymer, with d(33) remaining almost unchanged up to 125 ° C. The HFP copolymer exhibited poor retention of d(33) at temperatures above 80 ° C. In situ D-E loop measurements from -80 to +110 ° C showed that the remanent polarization of the TrFE copolymer was more stable than that of the PVDF homopolymer. D-E hysteresis loop and d(33) results were also compared with the deflection of the PVDF homopolymer and TrFE copolymer bimorphs tested over a wide temperature range. © 2005 Wiley Periodicals, Inc.