Group contribution method for the swelling behavior of thermo‐responsive hydrogels

Abstract

A group contribution method is introduced to describe the swelling behavior of thermo‐sensitive hydrogel systems. The accuracy of group contribution calculations is strongly dependent on the choice of thermodynamic model. Therefore, we revise the modified double lattice (MDL) model and develop a new expression for the interaction energy parameter using the association theory of Sanchez to take into account complex polymer/solvent mixing. The net Helmholtz energy for a hydrogel is established by combining the revised MDL model and modified Flory–Rehner elastic model. Group parameters are generated by fitting to experimental swelling data from both homopolymer and copolymer gel systems. The effect of salt on the volume phase transition is modeled by introducing an additional salt‐specific parameter to investigate various stimuli‐response swelling behavior. Calculated swelling equilibria using the new group contribution method shows excellent agreement with experimental data and various stimuli‐response volume phase transitions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 455–463

Equilibrium swelling of thermo-responsive copolymer microgels

“…An advantage of this approach is that the Hildebrand solubility parameter of comonomers can be evaluated straightforwardly by means of the group contribution method, 73 whereas the accuracy of this method for calculation of the FH parameter (by using the UNIQUAC equation or its modications 74,75 ) is rather modest. [76][77][78] Possible reasons for such an inaccuracy are discussed in ref. 79.…”

Swelling of Thermo-Responsive Gels in Aqueous Solutions of Salts: A Predictive Model

“…Symbols: experimental data on PNIPAAm gel [41] The material parameters for these gels were found by fitting the equilibrium swelling diagrams in pure water (Figure 1C,D) and are reported in Table S1. For each additive in aqueous solutions, the best-fit value of K was determined separately from the condition of minimum for functional (36). These values are collected in Tables S4 and S5.…”

“…Several models have recently been proposed to describe the complexation mechanism in ionic TR gels [31][32][33][34]. However, the effect of salts on the critical temperature of non-ionic TR gels and solutions of TR polymer chains was analyzed in only a few studies [35][36][37].…”

The effect of saccharides on equilibrium swelling of thermo-responsive gels

“…S-2B † shows that eqn (14) describes correctly an increase in c with temperature below the critical temperature T c . An advantage of the governing eqn (10), (14) and (16) compared with previous models for swelling of TR gels (see, for example, 55,56 where similar observations are approximated) is that it correctly describes equilibrium swelling diagrams by means of a rather limited set of adjustable parameters.…”