Solution Properties of Low Molecular Weight Fractions of Poly(2-vinylpyridine)

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The relationships between the weight-average molecular weight Mw and the intrinsic viscosity [η] of poly(2-vinylpyridine) [P2VP] in benzene and methyl alcohol at 25 °C, were investigated by the use of fractions with molecular weights ranging from 2.1×103 to 2.3×104. The exponent ν in the Mark-Houwink-Sakurada equation, [η]=K0Mwν, was 0.5 in both solvents when Mw was lower than about 104. A constant K0 was approximately in accord with Flory’s Kθ value for ordinary high-molecular-weight P2VP, obtained earlier in respective solvents. By measuring [η] for these low-molecular-weight fractions in several solvents at different temperatures, the temperature coefficients of an unperturbed dimension, dln20⁄dT, of this polymer were estimated and averaged to be −2.3×10−3 K−1. These are quite different from the positive values calculated from the Kθ’s by Dondos et al. which were estimated using the extrapolation method for non-θ-solvents. Our results were further corroborated after adding a Kθ value which was directly determined at another θ-state; i.e. in toluene at 63.7 °C, to that in benzene at 16.2 °C published earlier, which was found from phase-separation experiments in this work.