Synthesis and thermodynamic properties of poly(cyclohexylethylene-b- dimethylsiloxane-b-cyclohexylethylene)

Poly(styrene-b-dimethylsiloxane-b-styrene) (PS-PDMS-PS) triblock copolymers were prepared by anionic polymerization and subsequently hydrogenated using a platinum/rhenium catalyst supported on ultrawide pore silica (Pt/Re - SiO ₂), yielding PCHE-PDMS-PCHE, where PCHE refers to poly(cyclohexylethylene). The hydrogenation reaction resulted in polymer with negligible chain degradation as confirmed by ¹H NMR and size exclusion chromatography (SEC). Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) experiments revealed a lamellar morphology for all specimens. Thermodynamic properties were inferred from the order-disorder transition temperatures as determined by SAXS and dynamical mechanical spectroscopy (DMS). The resulting segment-segment interaction parameter, _x(T), is assessed in the context of current published approaches to treating the thermodynamics of nonpolar polyolefins, particularly block copolymers.