Evaluating Polymerization Methods and Deprotection Strategies for Making Water Soluble Poly(acrylic acid) with Hydrolyzable Breaking Points

Abstract

Poly(acrylic acid) (PAA) is a hydrophilic polymer widely utilized in various everyday applications, but it may persist in the environment due to its stable carbon-carbon (C-C) backbone. This work presents a detailed comparative study of introducing hydrolyzable ester breaking points into the PAA backbone using different radical copolymerization methods (bulk versus solvent and batch versus semi-batch) with varied feed ratios of tert-butyl acrylate (tBA) and 2-methylene-1,3-dioxepane (MDO) followed by the investigation of the removal of t-Bu group for getting free acid functionality in copolymers under different conditions. A detailed comparison of polymerization approaches (bulk versus solution, batch versus semi-batch) revealed that solution polymerization at 100 °C with tert-butyl peroxide provided high ring-opening efficiency (71%) and uniform molecular weight distribution. The study optimized deprotection processes for tBA to acrylic acid, achieving complete hydrolysis under mild conditions using 5 equivalents of trifluoroacetic acid in dichloromethane. The resultant polymers displayed pH and temperature dependent solubility and significant degradation under alkaline conditions, with the formation of oligomers (400–700 Da for 35% MDO content) suitable for microbial assimilation. These findings highlight a scalable pathway for creating environmentally degradable PAA alternatives with tailored properties for functional applications.