Dissolution of phenolic polymers in aqueous base: the influence of polymer structure

摘要

The differences in the dissolution behavior of novolac and poly(4-hydroxystyrene) (PHS) can be explained in terms of differences in the pK$-a$/ of the two polymers. The proximity of the hydroxyl groups in ortho-ortho bonded novolac causes a large change in the pK$-a$/ of the polymer as a function of the degree of ionization. The increased distance between phenolic sites in PHS attenuates this effect. Novolac and PHS samples have been titrated from basic to acidic conditions to determine the `apparent pK$- a$/' of each polymer as a function of degree of ionization, $alpha@. The turbidimetric endpoints show that novolac precipitates earlier in the titration than PHS. This differences provides an explanation for the `ortho-ortho effect' and the different inhibition efficiencies of these polymers.