Abstract
The poly(vinyl alcohol) (VTFA-PVA) derived from vinyl trifluoracetate and the poly(vinyl alcohol) (VAc-PVA) derived from vinyl acetate, that differ in the stereoregularity, were blended and fractionated by the stress-induced crystallization. The mixture of PVA's which have nearly the same degree of polymerization but different tacticity, especially, the different syndiotacticity (B-1) was separated clearly by stirring. On the other hand, when the degree of polymerization of raw PVA that had higher syndiotacticity was lower than that of raw PVA that has the lower syndiotacticity (B-2), the mixture was not separated clearly. The relation between the percentages of syndiotactic diads of the fractions and the cumulative weight fraction (CWF) for B-1 was represented with two different curves for CWF of below and above 50%, whereas the percentages of syndiotactic diads of the fractions for B-2 decreased monotonously in the order of fractionation. The relation between the degree of polymerization and CWF for B-2 was similar to that obtained in the stirring fractionation of VTFA-PVA. Therefore, VAc-PVA was crystallized together with VTFA-PVA by shearing force from the initial stage of fractionation, though the contents of VTFA-PVA in crystals were greater than those of VAc-PVA.
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