Structural characteristics of phenol formaldehyde novolak resin depending on polycondensation type using molecular simulation

Phenol formaldehyde novolak resins have various structures depending on the polycondensation types. Their structures were characterized using molecular mechanics and molecular dynamics. Dimer, tetramer, hexamer, octamer, and decamer of the resins with the ortho-ortho, ortho-para, and para-para sequences were calculated. The ortho-ortho resins have the structural characteristics of intramolecular hydrogen bonds between hydroxyl groups of the adjacent phenolic units. For the ortho-para and para-para resins, the intramolecular hydrogen bonds are formed mainly between hydroxyl groups of the backbone phenolic units. The para-para resins also have intramolecular hydrogen bonds between hydroxyl groups of the branched phenolic units. A factor determining the structural characteristics of the resins was found to be the geometry of the basic unit (dimer). The order of the end-to-end distances between hydrogen atoms on the para-position of the basic units of the resins is ortho-ortho resin < ortho-para resin < para-para resin. The calculational results were found to be consistent with the gel permeation chromatography (GPC) analysis. Copyright (C) 2001 John Wiley & Sons, Ltd.