Stimuli-responsive lyogels are smart materials that undergo significant changes in response to external triggers, showing promise in applications like drug delivery and actuation. Poly-N-isopropylacrylamide (pNIPAM), known for its thermo-responsiveness, also swells in polar solvents due to hydrogen bonding, while nonpolar solvents cause shrinkage. This study aims to model this behavior for future use in (bio-)chemical reactors, enhancing reactor systems with smart lyogel technology. Using thermodynamic modeling (gE model COSMO-RS), we observe the correlation between solvent-polymer interactions and swelling. pNIPAM derivatives show low infinite dilution activity coefficients (IDACs) in polar solvents with high swelling, while IDACs increase in nonpolar solvents. Hydrogen bonds significantly influence swelling, even in solvent mixtures with high nonpolar content, where polar solvent uptake leads to notable swelling. This behavior is evident in binary mixtures and during esterification reactions with varying alcohol and acid chain lengths.
Eckert, K. M., Müller, S., Luinstra, G. A., Smirnova, I. (2024). Exploring pNIPAM lyogels: Experimental study on swelling equilibria in various organic solvents and mixtures, supported by COSMO-RS analysis. Fluid Phase Equilibria 586, 114182.
