Grafting of shape memory polyurethane with poly(ethyleneimine) and the effect on electrolytic attraction in aqueous solution and shape recovery properties

Shape memory polyurethane (SMPU) grafted using polyethyleneimine (PEI) was tested for its electrolytic attraction in aqueous solution and shape memory effect. The PEI was connected through a second 4,4'-diphenylmethane diisocyanate anchored to the carbamate moiety of SMPU. Two series of SMPU that differed in soft segment polytetramethylene glycol and PEI content were prepared to compare their tensile and shape memory properties. Shape recovery was high as 99% and reduced only to 97% after four test cycles. The PEI group attached to the SMPU chain, if converted to the imminium salt form, was designed to work as an electrolyte during water electrolysis and was to be attracted toward the cathode to show SMPU movement in aqueous solution. The electrolytic attraction of SMPU in aqueous solution was demonstrated in an experiment in which a specimen moved to the cathode only when voltage above a minimum was applied. The mechanism and application of this finding are discussed.