The Flory constants for poly‐4‐vinylpyridine in ethanol

Vinylpyridine was polymerized in suspension, using azobis-iso-butyronitrile as initiator. The polymer was fractionated by partial precipitation from methanol solutions by addition of toluene to cloud point in chilled solution and then raising the temperature. Viscosities of four fractions were determined at 25, 50, and 70° in absolute ethanol. Rayleigh ratios and scattering asymmetry were determined for eight fractions; from the corresponding Zimm plots, molecular weights, coil diameters, and virial coefficients were determined. Addition of ammonia was found necessary at low concentrations to suppress ionization due to traces of acid impurities. Addition of water (a nonsolvent) lowers the second virial coefficient. Molecular weights were determined for two fractions by osmotic pressure. In absolute ethanol, the results are summarized by the equation [η] = 2.5 × 10−4M0.68; experimental range 0.102 ⩽ 106M ⩽ 1.85. The second virial coefficient from light scattering was 4.2 ± 0.3 × 10−4, independent of molecular weight; the osmotic values agreed within experimental error. The Flory constant was found to be 2.1 ± 0.3 × 1021. Extrapolation for the θ-point leads to the rough estimate θ ≈ −50°C. Evidence is presented which shows that polyvinylpyridine degrades slowly in solution.