Preparation and Characterization of Narrow Compositional Distribution Polyampholytes as Potential Biomaterials: Copolymers of N-(3-Aminopropyl)methacrylamide Hydrochloride (APM) and Methacrylic Acid (MAA)

摘要

This article describes the preparation and solution properties of a series of polyampholytes composed of N-(3-aminopropyl)methacrylamide hydrochloride (APM) and methacrylic acid (MAA). In particular, conditions were found where the copolymers could be formed with little or no drift in composition over the course of polymerization to quite high conversions. The compositional drift, common to many copolymerizations, was limited by adjusting the reactivity of MAA through control of its degree of ionization (i.e., pH). As revealed by potentiometric measurements and changes in H-1 NMR spectra, the solution pH drifted over the course of some polymerizations. This was ascribed to changes in the pK(a) values of the ammonium and carboxylate groups upon incorporation in the copolymer. The pH drift led to a change in degree of MAA ionization, and hence the relative reactivities of APM and MAA, but this effect could be minimized by using a buffer. Precipitation, which occurred during some polymerizations, could be prevented, in some cases, by the addition of salt or an organic cosolvent. Even in cases where precipitation could not be prevented, it was found that the copolymer was still formed with minimal compositional drift. The solubility of the resulting polyampholytes in aqueous solution was found to depend on their composition, as well as pH, ionic strength and temperature. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 353-365