A Comparative Study of Two Synthesis Methods for Poly(Acrylic Acid-Co-Acrylamide) Incorporating a Hyperbranched Star-Shaped Monomer

The synthesis of poly(acrylic acid-co-acrylamide) was investigated to enhance itsrheological properties. Syntheses were conducted in both aqueous and supercritical fluidmedia, with and without the incorporation of a novel star-shaped macromonomer. Themacromonomer, synthesized from a Boltorn H30 core with PEGMA500 arms and modified to contain a single vinyl group, was copolymerized with acrylic acid and acrylamide. Comprehensive polymer characterization was performed using FTIR, NMR, and SEC-MALS-dRItechniques. Rheological assessments revealed that copolymers containing the star-shapedmonomer exhibited significantly higher viscosities than those lacking the hyperbranchedcomponent, a result attributed to the inter- and intrachain interactions facilitated by thePEGMA500 arms. Additionally, purification studies demonstrated that dialysis was neces-sary to remove short-chain polymers, particularly for samples synthesized in supercriticalmedia, to achieve optimal rheological performance. Polymers synthesized in a supercriticalCO2–ethyl acetate mixture exhibited higher viscosities compared to their water-synthesizedcounterparts. The integration of the novel star-shaped macromonomer into HPAM-likepolymers offers substantial potential for enhanced oil recovery applications.