Abstract
AbstractIntrinsic viscosity against temperature plots for two sequence block copolymers of isoprene and styrene in decalin and methyl cyclohexane confirm the general behaviour of these polymers in preferential solvents. The operative parameters are the mol. wt., composition and ⊖ temperature of the less soluble polymer in the particular solvent. The STOCKMAYER‐FIXMAN relation [η]M = Φ0(A + 0.51 BηM)is obeyed, for a particular composition, at all temperatures, but the unperturbed dimensions in the block appear to drop significantly at temperatures below the transition temperature. Since the constant Φ0 is influenced by the segmental distribution, the drop in unperturbed dimensions may be considered to reflect the conformation change from the phase‐mixed to phase‐separated form. The characteristic ratio, C∞ = 〈r2〉0/nl2, which is calcd. from K in the KUHN‐MARK‐HOUWINK Eq. determined directly from [η]0 (⊖ = 44°C in methyl ethyl ketone) is identical with that obtained by extrapolation using the STOCKMAYER‐FIXMAN relation at 46°C. Moreover, C∞ may be calcd. directly from C∞Block = xC∞PS + (1 − x) C∞PI after taking account of the isomeric composition of the polyisoprene.
Published Version
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