NOVEL THERMOPLASTIC ELASTOMER RESULTING FROM PHYSICAL GELATION OF TELECHELICALLY LABELED POLYDIMETHYLSILOXANE

摘要

Polydimethylsiloxane (PDMS) that has been labeled on both chain ends with a pyrene-based dye yields a novel thermoplastic elastomer. This behavior is due to thermoreversible physical gelation in the bulk state associated with nanocrystal formation of the pyrene dyes that are strongly insoluble in the PDMS. The gelation temperature, which is equal to the nanocrystal melting temperature, can be tuned by varying the PDMS molecular weight. At the nanocrystal melting temperature, a greater than three order of magnitude change in the value of tan δ is observed from oscillatory shear flow measurements. Significant hysteresis is observed upon heating and cooling due to the time needed to achieve equilibrium nanocrystal formation.