Exploring the Physicochemical and Rheometric Properties of Acrylic Acid - co - 2-Acrylamido-2-methylpropane Sulfonic Acid Copolymers Synthesized in Supercritical Carbon Dioxide

RAMSES SEGUNDO MELEÁN BRITO; FACUNDO MATTEA; JUAN MANUEL PADRÓ; MIRIAM STRUMIA; SÉVERINE CAMY; MATHIAS DESTARAC; JUAN MANUEL MILANESIO

Los Cocos

Conferencia; VI Iberoamerican Conference on Supercritical Fluids (PROSCIBA 2023); 2023

IPQA y Universidad Nacional de Córdoba

Acrylic acid (AAc) and 2-acrylamide-2-methylpropane sulfonic acid (AMPS) are commonly polymerized using solution or precipitation techniques employing either water or organic solvents. Among these techniques, solution polymerization is the most prevalent because of its economic and technical viability. Depending on the solvent (water or organic) an appropriate thermal initiator should be used, such as azo compounds, peroxides, and persulfates. For solution polymerization peroxides and persulfates are the most common initiators and after the reaction concludes, a precipitation followed by a drying process are mandatory due to the solubility of the polymer in water. On the other hand, the most common thermal initiators for precipitation polymerization are azo compounds. At the beginning of the reaction a homogeneous mixture of solvent, monomers and initiator is prepared. As long as the reaction proceeds, the polymer precipitates, resulting in a solid or liquid polymer-rich phase. An energy-intensive drying process is necessary at the end of the reaction. Alternatively, compressed solvents, such as carbon dioxide, can be employed as solvents for precipitation polymerization. Owing to its adjustable density and solvent power, carbon dioxide can solubilize acrylic acids and other vinylic monomers. One key advantage of using carbon dioxide is its ability to produce high-purity products by a simple depressurization of the system, without any further precipitation nor drying process. Additionally, carbon dioxide can be recycled by recompression and reduces the reliance on toxic organic solvents that are detrimental to the environment and human health.As demonstrated by Robert´s group in the early 2000s, scCO2 acts as an inert solvent not showing radical transfer to the solvent , making it a suitable choice for the radical precipitation polymerization of AAc. The same observation was confirmed by Ollagnier et al. in 2016. Their findings demonstrated that scCO2 allows the synthesis of polymers with high average molecular weights.This study focuses on the copolymerization of AAc with AMPS in scCO2. This study evaluated the influence of AMPS content in the initial reaction mixture, ranging from 10% to 50% AMPS, and investigated its incorporation into the polymer chain using FTIR and 1H-NMR techniques. Subsequently, the viscosity of the resulting polymeric solutions in water was examined using rheology measurements, studying the impact of pH and salinity. The experimental data reveal biphasic behavior as the 2-acrylamide-2-methylpropane sulfonic acid content increases during polymerization, leading to a reduction in the viscosity of the resulting copolymer in the aqueous solution. However, there are indications that an increase of up to 30% in the AMPS content results in high viscosities under specific pH and salinity conditions