Microphase-separated structure of 1,3-cyclohexadiene/butadiene triblock copolymers and its effect on mechanical and thermal properties

We report the effect of microphase-separated structure on the mechanical an d thermal properties of several poly(1,3-cyclohexadiene-block-butadiene-blo ck-1,3-cyclohexadiene) triblock copolymers (PCHD-block-PBd-block-PCHD) and of their hydrogenated derivatives: poly(cyclohexene-block-ethylene/butylene -block-cyclohexene) triblock copolymers (PCHE-block-PEB-block-PCHE). Both m echanical strength and heat-resistant temperature (ex. Vicat Softening Temp erature: VSPT) tended to increase with an increase in the 1,3-cyclohexadien e (CHD)/butadiene ratio. On the other hand, heat resistance of the hydrogen ated block copolymer was found to be higher than that of the unhydrogenated block copolymer. However, the mechanical strength was lower than those of the unhydrogenated block copolymer with the same ratio of CHD to butadiene. To clarify the relationship between the higher order structures of those b lock copolymers and their properties, we observed the microphase-separated structure by transmission electron microscope (TEM). Hydrogenated block cop olymers were found to have more finely dispersed microphase-separated struc tures than those of the unhydrogenated block copolymers with the same CHD/B d ratios through the use of TEM and the small-angle X-ray scattering (SAXS) technique. Those results indicated that the segregation strength between t he PCHE block sequence and the FEB block sequence increased, depending on h ydrogenation of the unhydrogenated precursor. (C) 2000 John Wiley & Sons, I nc.