Synthesis and characterization of a new high temperature shape memory polyimide

High temperature shape memory polymers (SMPs) have wide potential applications in various fields, and glass transition temperature (T_g) is a crucial factors in determining their potential applications. Here we report a kind of new shape memory polyimide with a high glass transition temperature (T_g) of 316 ºC. The polyimide possesses thermal stable but flexible linkages within the backbone, and the number average molecular weight is 61.5 kg mol^-1. The tensile storage modulus of the polyimide decreases slowly with the increase of temperature at glass state, and a sharp glass-rubber transition is observed with a plateau at rubbery state. The storage modulus at 50 ºC, 260 ºC and 340 ºC are 2.3 GPa, 1.3 GPa and 10.1 MPa, respectively. The polymer possesses high thermal stability with the decomposition temperature of 519 ºC, and the pyrolysis left 56 % carbonaceous char from the aromatic group at 700 ºC. The sample shows nice shape memory properties with a strain recovery rate of 96.1 % and a strain fixing rate of 97.2 %. The mechanism of high temperature shape memory effect of polyimide is proposed, which will stimulate further research on high temperature SMPs.