Abstract
The determination of the branch density was performed using 13C-NMR spectroscopy for high-ortho and random novolacs prepared by the conventional zinc acetate-catalyzed and oxalic acid-catalyzed polycondensation, respectively. The phenoxy carbon chemical shifts were assigned using several kinds of novolacs having different molecular weights and ortho ratios of methylene linkage. In dioxane, the phenoxy carbon chemical shifts of the branched, linear, and terminal phenolic units were 149.2-151.4 ppm, 151.4-153.8 ppm, and 153.8-156.7 ppm, respectively. The molar percentages of the branched, linear, and terminal phenolic units in novolacs were dependent on the molecular weights of the novolacs. However, there was no difference in the branch density between high-ortho and random novolacs.
