Abstract
Novolak-type phenolic resins were synthesized by two different methods using heteropoly acids. In the homogeneous reaction system, phenol quickly reacted with paraformaldehyde. But the molecular weight distributions of the obtained resins were as broad as that of the resin prepared by oxalic acid. In the phase-separating reaction, phenol was consumed quickly and almost quantitatively. Additionally, the molecular weight distributions were narrow. 13C NMR spectra showed that the resins prepared by phase-separating reaction had less o-o' linkage and branched phenol unit than the resin obtained by homogeneous reaction
