Simulation of the effect of different parameters on the swelling characteristics of a pH-sensitive hydrogel

Hydrogels are 3-D network polymeric materials that exhibit a large volume phase-transition due to a of change in their environment so that the response causes the hydrogel to swell or shrink. Since hydrogels have been found to be useful for chemical sensing and delivery, there is a growing interest in their use for medicine. This ,requires a thorough understanding of the hydrogels characteristic response to pH. The hydrogel response can be explained by various physical equations which are often challenging to solve. We discuss the simulation of such phase-transitions in steady-state conditions emphasizing the response to solvent pH and other environmental stimuli. We demonstrate a method for simulating pH response of hydrogels and describe numerical model and its implementation in detail. Though a few models have been developed for simulation of these hydrogel characteristics, these have been based on custom programs implemented in individual laboratories and often not generally accessible. Hence, our modeling effort is implemented using the generic finite element software COMSOL and the method can be used with any software having similar capabilities. The effect of buffer solution concentration, fixed charge density, the solution pH on the swelling characteristics are studied. Results are compared with published experimental data.

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