The hydrogen bond formation between novolac type phenolic resin (phenolic) and polyhydroxyl ether of bisphenol A (Phenoxy resin) were verified by infra-red (i.r.), gel permeation chromatography (g.p.c.) and nuclear magnetic resonance (n.m.r.). The i.r. spectrum of the 'free' hydroxyl group of the blend shows a maximum absorption area with 25 wt% phenoxy which coincides with the lowest point of the glass transition temperature (T-g) is observed. In the phenolic-rich region, almost all the hydroxyls of the phenoxy interact with the phenolic resin. The carbonyl group of benzoylated phenoxy (Bz-phenoxy) confirms further the association of hydrogen bonding with hydroxyls of phenolic resin. It was found that phenolic resin interpenetrates with the phenoxy and Bz-phenoxy and causes significant decreasing of T-g. (C) 1997 Elsevier Science Ltd.