DEUTERATION EFFECTS AND SOLUBILITY PARAMETER ORDERING IN BLENDS OF SATURATED-HYDROCARBON POLYMERS

This paper presents a continuation of earlier studies on the effects of deuterium substitution on blends of saturated hydrocarbon polymers. The components were model polyolefins, each available in fully hydrogenous (h) and partially deuterated (d) forms, made by saturating the double bonds of polydienes with H-2 and D2. Values of chi, the Flory-Huggins interaction parameter, were obtained by small-angle neutron scattering with blends of the h form for one component and the d form for the other. According to our earlier proposal, the change in interaction when the deuterium labeling of the pair is reversed, chi1h,2d - chi1d,2h, permits a numerical ordering of the component solubility parameters, delta1 and delta2: chi1h,2d > chi1d,2h implies delta1 > delta2. The qualitative consistency of orderings based on this principle, involving blends with common components in many cases, was examined. Although disagreements with group contribution estimates were observed, the internal consistency of the orderings was clearly established for many model random and alternating copolymers. Only in the case of model head-to-head polypropylene were there clear conflicts in ordering assignments, which we had tentatively attributed to specific mixing effects.