A novel low colored and transparent shape memory copolyimide and its durability in space thermal cycling environments

Recently, shape memory polymers (SMPs) with high optical transmittance have been paid great attentions to endow the flexible optoelectronics with shape memory functions. Herein, a low colored and transparent shape memory copolyimide (SMcoPI) is obtained by suppressing the charge transfer complex interactions. The optical transmittance of the synthesized SMcoPI film could reach at ∼86% at the wavelength of 450 nm, far higher than the nearly zero optical transmittance of yellow and brown Kapton H. The better optical transparency could be attributed to the loose molecular chain arrangements induced by the meta-substituted groups and flexible ether linkages. The glass transition temperature (T_g) range of the synthesized SMcoPI films is from 179 °C to 220 °C, which is higher than that of reported optically transparent SMPs. The effective decomposition temperature at the weight loss of 5 wt% is 517 °C, showing excellent thermal stability. The SMcoPI also demonstrated good shape memory behaviors with high shape recovery ratio (R_r, >96%) and shape fixity ratio (R_f, >97%). In addition, the SMcoPI could maintain high optical transmittance, good thermostability and excellent shape memory behaviors after the ground-stimulated space thermal cycling test for 250 h. The synthesized SMcoPI has application potentials in high temperature areas or optoelectronic devices.