Block copolymer of trans-polyisoprene and urethane segment:: Shape memory effects

Shape memory behaviors of trans-polyisoprene (TPI) segmented urethane copolymers were studied. Film specimens for cyclic loading tests were prepared from the polymer solution by casting, and tested at the loading temperature of 65 degrees C. Results show that the recovery rates of the films depend on their TPI segment contents, while the fixity rate, vas measured to be close to 100% for each sample. The film containing 70% TPI segments was found to show a recovery rate of 85%. Two separated phases were clearly observed in the morphology of the films. The urethane segments were organized into spherical domains acting as physical cross-links during the shape memory process. The continuous phase formed by the crystalline TPI segments serves as the reversible phase responsible for fixation of the temporary shape. The tensile and dynamic thermal properties of those films were also studied. (c) 2006 Wiley Periodicals, tnc.