Phase boundaries and copolymerization of acrylic acid + butyl methacrylate in supercritical carbon dioxide under high-pressure single-fluid initiation

Associative polymers based on acrylic acid and n-butyl methacrylate were synthesized via precipitation polymerization in pressurized carbon dioxide. Physicochemical characterization confirmed BMA incorporation and good reaction yields (>67.1 mol%). Size exclusion chromatography showed bimodal polymer molar mass distribution with distinct average molar masses. Rheological properties of aqueous polymer solutions were assessed under varying pH, ionic strength, and salt concentrations and demonstrated increased viscosity with higher n-butyl methacrylate content, attributed to hydrophobic associations. The apparent viscosity of the synthesized polymers was strongly influenced by the ionic strength of the aqueous solutions. [Display omitted] •Polymers of acrylic acid and butyl methacrylate were obtained in supercritical CO2.•Phase equilibria for scCO2 + butyl methacrylate + acrylic acid were measured.•Mw of the polymers yield values up to 2 ×106 g mol−1.•SEC-MALS-dri revealed distinct polymer populations with increased BMA in the feed.•The viscosity of aqueous solutions of the polymers increased with increasing BMA.