Heterogeneity analysis of polymeric carboxylic acid functionality by selective derivatization followed by size exclusion chromatography.

Waterborne polymers are increasingly applied in our society, replacing traditional solvent-borne coatings and thus reducing environmental impact of coatings. The majority of waterborne dispersions are stabilized by the incorporation of neutralizable carboxylic acid functionality. The characterization of synthetic waterborne polymer systems can be performed by a wide variety of chromatographic and spectroscopic techniques. However, none of these approaches is able to determine the acid functionality distribution over the molecular-weight distribution directly. In this research, an innovative approach is developed which enables this analysis. The approach is based on the specific and complete derivatization of carboxylic acid functionality with phenacylbromide. Size exclusion chromatography (SEC) analysis of the derivatized polymers is performed followed by ultraviolet- (UV) and refractive index (RI) detection, enabling the quantitative determination of the acid content per molecular weight fraction. The applicability of the developed protocol is shown for various polymer systems.