Determination of the Flory-Huggins interaction parameter of styrene and 4-vinylpyridine using copolymer blends of poly(styrene-co-4-vinylpyridine) and polystyrene

On the basis of the experimentally determined phase behavior in blends of polystyrene and random copolymers of styrene and 4-vinylpyridine, i.e., P(S-x-co-4VP(1-x))/PS, the Flory-Huggins interaction parameter is demonstrated to satisfy 0.30 < chi(S,4VP) less than or equal to 0.35. This value is substantially smaller than reported before. To corroborate our results, a similar study was performed using 2-vinylpyridine leading to 0.09 < chi(S,2VP) less than or equal to 0.11, in excellent agreement with the well-established value of chi(S,2VP) = 0.1.