On the Mechanism of Dissolution Inhibition in Phenolic Resins

Abstract

Until quite recently it was believed that dissolution inhibition in phenolic resins is based on a general hydrophobic effect of the inhibitor. Honda et al. [5] have now shown that the hydrophobicity of an additive is not sufficient and that the polar functional groups of the inhibitor play an important role in the inhibition effect. They found that additives with very similar skeletal structures, and therefore with similar hydrophobicity, but which differ in their polar functional groups, have very different inhibition efficiencies in a common novolak resin. In an earlier communication [4] it was suggested that inhibition in phenolic resins comes about by the blocking of some of the hydrophilic OH-groups. Such blocking action by the inhibitor presupposes interaction between the inhibitor and the phenols of the resin. Here we investigate this interaction by determining the associated equilibrium constants in dilute solution. From these data the fraction of phenol-bound inhibitors in the casting solutions of the films can be estimated. For the group of additives investigated by Honda et al. [5] the fraction of phenol-bound inhibitors correlates quite satisfactorily with the inhibition effect. © 1993, The Society of Photopolymer Science and Technology(SPST). All rights reserved.