Studies of Poly-2-vinylpyridine. I. Suspension Polymerization and Molecular Weight Distribution

Abstract 2-Vinylpyridine has been polymerized by the suspension method. A stable suspension has been obtained using a mixture of sodium butylnaphthalene sulfonate and gelatine as a stabilizer in the concentration ranges of 0.025–0.75 per cent (for the former) and 0.75–1.0 per cent (for the latter) in water. The molecular weight of polymers thus obtained from this stable suspension system could be controlled by varying the concentration of azo-bis-isobutyronitrile and the temperature. The Mw/Mn ratios of the polymers obtained by the above method are relatively large; from 3.5 to 5. Precipitation fractionation has been carried out for a polymer obtained using ethyl methyl ketone as a solvent and ligroin as a precipitant at a constant temperature. Three kinds of molecular weight distribution curves have been obtained by applying the data of fractionation to (1) Tung’s method, (2) exponential-type and (3) logarithmic normal-type molecular weight distribution functions. By comparing the average molecular weights, Mw and Mn calculated from each curve with the experimental values, it was found that the molecular weight distribution of the fraction can be well represented by the function 2 or 3.