DETERMINATION OF CRESOL NOVOLAK COPOLYMER COMPOSITION AND BRANCH DENSITY USING C-13 NMR-SPECTROSCOPY

Carbon-13 NMR spectroscopy is used to determine hitherto unmeasurable novolak copolymer compositions and the m-cresol novolak polymer branch density for soluble samples. The estimate of variance in cresol novolak copolymer compositions determined this way is ca.1% of the value. For copolymers containing phenol, the estimate of variance is ca. 10% of the value. Analysis of the competition for formaldehyde between sites on the same phenolic monomer and between different phenolic monomers yields the relative reactivities of the sites and the monomers. The reactivities of o-cresol, m-cresol, and p-cresol relative to phenol are 2.36 +/- 0.05, 6.03 +/- 1.78, and 0.47 +/- 0.01, respectively.