Molecular thermodynamic analysis for reentrant and reentrant-convex type swelling behaviors of thermo-sensitive hydrogels in mixed solvents

Enhanced solvation effect of re-collapsing behavior for cross-linked PMMA particle gel in aqueous alcohol solutions

“…Detailed derivation is given in previous works of our group [24,25]. To determine the swelling equilibrium of the gel system, the following condition is used.…”

“…In lattice model, the molecular size parameter of the smallest molecule is defined as a unity. In this system, we set r 3 ¼ 1 for water and those for other molecules (r i ) are determined as below [24,53]. The values are listed in Table 1.…”

“…This might be attributed to the fact that MDL takes account of the effect of specific interactions such as hydrogen bonding by introducing secondary lattice term. In addition, in our previous work [24,25,27], MDL was successfully employed to calculate cononsolvency phase behavior and reentrant swelling behavior by directly applying interaction parameters from binary system. Therefore, in the further phase diagrams, MDL was used as a thermodynamic model for LLE.…”

“…Maurer et al [22,23] employed the excess Gibbs energy model based on the UNIQUAC equation with a free volume contribution to describe their reentrant swelling data. Recently, Oh and Bae [24] and Kim and Bae [25] developed a new method of calculating the reentrant type of swelling behavior for PNIPA cross-linked gels. In this work, they obtained intermolecular interaction parameters from linear PNIPA binary solution and directly applied them to the cross-linked gel system.…”

“…This approach minimizes fitting parameters so that various swelling properties can be predicted. However, the model correction to consider the composition dependence of interaction parameter was not consistently applied to the crosslinked and uncrosslinked polymer system [24], and the influence of structural and chemical nature of solvent on the swelling behavior was not investigated [25]. Moreover, experimental and theoretical approaches [26e28] using the complete ternary diagram are very scarce, and there have been no studies about the swelling behavior of a cross-linked gel in cosolvent system.…”