Swelling–deswelling behavior of poly(acrylamide‐co‐maleic acid) hydrogels

Abstract

ABSTRACT:In this study the poly(acrylamide-co-maleic acid) hydrogels containing small amounts of maleic acid have been synthesized, and the effect of pH, ionic strength, and nature of counterions on the equilibrium water uptake has been investigated. The incorporation of small amount of maleic acid results in the transition of swelling mechanism from Fickian to non-Fickian. The equilibrium mass swelling has been found to increase with pH of the swelling medium while increase in ionic strength causes a decrease in the swelling. The amount of maleic acid present in the hydrogel affects the swelling behavior in rather an unusual way. With lower acid contents, the equilibrium mass swelling increases while higher concentrations of maleic acid cause a decrease in the degree of swelling. The hydrogels have been found to undergo a number of swelling-deswelling cycles when pH of the swelling medium changes from 8.0 to 2.0. Hydrogels require more time to deswell compared to the time required for swelling, which has been explained on the basis of the fact that gels follow different mechanisms for the two processes. Various swelling parameters such as equilibrium mass swelling, diffusion coefficient, intrinsic diffusion coefficient, swelling exponent, etc., have been evaluated.

Multiphysics Modeling of Electrochemomechanically Smart Microgels Responsive to Coupled pH/Electric Stimuli

“…4:0 are totally ionized, which may be the reason for the small increase of K a in the range of pH ¼ 5.0 to 9.0. The predictions by the present simulations are consistent with the experimental phenomena, [53] in which it is reported that the local pH gradient attributed to water electrolysis may be an additional factor to influence the bending deformation. [54] Figure 15 is plotted for the coupled effect of the initially fixed charge density c s f and electric voltage V e as well as solution pH on variation of the average curvature K a with pH ¼ 4.0 and V e ¼ 0:4 V. It is shown by the Figure that the average curvature K a increases with the initially fixed charge density c s f .…”

Colon‐specific oral delivery of vitamin B2 from poly(acrylamide‐co‐maleic acid) hydrogels: An in vitro study

“…In our previous communication, 3 we described a detailed study of the swelling behavior of poly-(acrylamide-co-maleic acid) hydrogels. However, in a preliminary study for the present work, a number of hydrogels with different amounts of the monomers AAm and MA and the crosslinker MB were synthesized and their equilibrium swelling was determined in the swelling media of pH 2.0 and 7.4 so as to obtain the maximum difference between the percent mass equilibrium swelling at pH 2.0 and 7.4.…”

“…3 However, in brief, 4.50 g of the monomer AAm and 0.10 g of MA were dissolved in water to give a clear solution. To this, 0.15 g of the crosslinker MB and 0.10 g of the initiator KPS were added and the resulting solution, after being made up to 30 mL, was poured into PVC straws, each of 5.30-mm diameter, and kept in an electric oven (Tempstar, India) for a period of 4 h at 60°C.…”

Gelatin Hydrogel Prepared by Photo‐initiated Polymerization and Loaded with TGF‐β1 for Cartilage Tissue Engineering

“…[33] The swelling ratio decreased along with polymer concentration as shown in Figure 3a. This is understandable since the crosslinking density per volume is improved, which enables the hydrogel less swelling.…”