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

This paper presents a continuation of earlier studies on the effects o f deuterium substitution on blends of saturated hydrocarbon polymers. The components were model polyolefins, each available in fully hydroge nous (h) and partially deuterated (d) forms, made by saturating the do uble bonds of polydienes with H-2 and D2. Values of chi, the Flory-Hug gins interaction parameter, were obtained by small-angle neutron scatt ering with blends of the h form for one component and the d form for t he 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 paramete rs, delta1 and delta2: chi1h,2d > chi1d,2h implies delta1 > delta2. Th e qualitative consistency of orderings based on this principle, involv ing blends with common components in many cases, was examined. Althoug h disagreements with group contribution estimates were observed, the i nternal consistency of the orderings was clearly established for many model random and alternating copolymers. Only in the case of model hea d-to-head polypropylene were there clear conflicts in ordering assignm ents, which we had tentatively attributed to specific mixing effects.