Multishape Memory Effect of Norbornene-Based Copolymers with Cholic Acid Pendant Groups

Multishape memory copolymers were prepared through copolymerization of two norbornene derivatives: one based on cholic acid and the other on triethylene glycol monomethyl ether. The glass transition temperature (T-g) of the copolymers can be tuned over a temperature range from -58 to 176 degrees C. Most of these copolymers displayed a very broad T-g over a 20 degrees C range which can allow a multishape memory effect. The shape memory properties of the copolymer incorporating an equal molar amount of both monomers have been studied in detail. The multishape memory effect was investigated by dynamic mechanical analysis using a thermomechanical programming process, in which multiple steps created two, three, and four temporary shapes. The polymer displayed good shape fixing and recovery in different thermal processing stages over the broad glass transition range. This series of copolymers with broad and tunable T-g's may be useful as functional materials with multishape memory effect.