Ramses S. Meleán Brito

The development of associative polymers remains a critical challenge for enhanced oil recovery, where macromolecular stability must be maintained under thermal and saline stresses. In this study, a multiscale analysis of the structure–property relationship is conducted for poly(acrylamide-co-acrylic acid) (HPAM) copolymers modified with three hyperbranched architectures: Behera’s Amine (dendron), Boltorn H30 (hyperbranched aliphatic polyester), and Tannic Acid (polyphenolic pseudo-dendrite). Rheological evaluations reveal that while all associative copolymers outperform HPAM, their performance is governed by a complex interplay of bond energy and conformational exposure rather than molar mass alone. Tannic Acid-HPAM exhibit the greater viscosifying performance across varying pH, salinity, and temperature, because of its high-energy π–π stacking and phenolic hydrogen bonding. While Boltorn H30 showed superior thermal resistance due to its sterically confined hyperbranched architecture; Behera’s Amine analogues exhibited the lowest thermal resistance due to the dissociation of low-energy tert-butyl clusters. Molecular dynamics simulations provide a foundation for these findings, identifying solvent-accessible surface area as a primary predictor of network efficiency. Results demonstrate that Tannic Acid systems adopt conformations maximizing the exposure of interaction sites, facilitating transient intermolecular networks. This study establishes a guide for designing associative architecture, highlighting the synergy between bond energy hierarchy and conformational availability as essential for the next-generation EOR polymers.

The synthesis of poly(acrylic acid-co-acrylamide) was investigated to enhance its rheological properties. Syntheses were conducted in both aqueous and supercritical fluid media, with and without the incorporation of a novel star-shaped macromonomer. The macromonomer, 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-dRI techniques. Rheological assessments revealed that copolymers containing the star-shaped monomer exhibited significantly higher viscosities than those lacking the hyperbranched component, a result attributed to the inter- and intrachain interactions facilitated by the PEGMA⁵⁰⁰ arms. Additionally, purification studies demonstrated that dialysis was necessary to remove short-chain polymers, particularly for samples synthesized in supercritical media, to achieve optimal rheological performance. Polymers synthesized in a supercritical CO₂–ethyl acetate mixture exhibited higher viscosities compared to their water-synthesized counterparts. The integration of the novel star-shaped macromonomer into HPAM-like polymers offers substantial potential for enhanced oil recovery applications.

Acrylamide polymers are typically used in industrial and healthcare sectors as thickening agents; however, their thickening capabilities rely mainly in their molecular mass. A versatile and simple strategy to improve their performance is the copolymerization with specific monomers or their chemical modification with structures like dendritic or hyperbranched molecules. This study introduces a novel acrylamide‐acrylic acid polymer grafted with minor proportions (≤4.0 wt%) of Boltorn H30, a hyperbranched polyester monomer. The incorporation of Boltorn H30 aims to exploit the hyperbranched architecture's impact on the viscosity and rheological behavior of polymer solutions. Polymers with 0.4 and 4.0 polyester wt% characterized by several analytical techniques displayed improved viscosity in aqueous solution compared against the parent poly(acrylamide‐co‐acrylic acid). Results revealed that while the molecular mass distribution changed between 20% and 94%, the thickening capabilities significantly improved with increments of 2.7 and 3.8 times compared to that of the original polymers. These findings demonstrate that even with a minimal incorporation of hyperbranched polyesters, the abundance of hydroxyl groups fosters extensive hydrogen bonding, resulting in enhanced viscosity properties of the polymer.