Heterogeneous Catalytic Hydrogenation of Poly (styrene): Thermodynamics of Poly(vinylcyclohexane) Containing Diblock Copolymers

Heterogeneous catalytic hydrogenation of 1,4-poly(isoprene) (PI), atactic poly(styrene) (PS), and two poly(styrene)—poly(isoprene) (PS—PI) diblock copolymers was performed using two palladium supported catalysts. In each case fully saturated materials were obtained with no chain degradation. The dynamic and thermodynamic properties of these materials were investigated using differential scanning calorimetry and dynamic mechanical spectroscopy. Saturated poly(styrene), denoted poly (vinylcyclohexane) (PVCH), exhibited a glass transition temperature (T_g) that is 40 deg higher than that of poly(styrene). For diblock copolymers of PVCH and poly(ethylene—propylene) (PEP) this increase in T_g is accompanied by a slight increase in the order—disorder transition temperature, T_ODT, relative to that characterizing the PS—PI precursor. Estimates of the associated segment—segment interaction parameters based on group contribution methods anticipate a steep reduction in T_ODT with saturation, contrary to this result.