Synthesis, swelling behavior, and network parameters of novel chemically crosslinked poly (acrylamide-co-methacrylate-co-acrylic acid) hydrogels

Abstract

The purpose of this study was to prepare a series of pH-sensitive hydrogels from acrylamide, methacrylate, and acrylic acid using different crosslinking agents. Hydrogels were prepared by free-radical copolymerization in alcoholic solution in the presence of a redox initiator, benzoyl peroxide, and crosslinkers, ethylene glycol dimethacrylate (EGDMA), and diethylene glycol dimethacrylate (DEGDMA). The effect of pH and the nature of the crosslinker on the swelling behavior of the copolymeric gels were investigated. Equilibrium swelling studies, in the pH range of 1–8, were performed to determine the average molecular weight between the crosslinks (Mc), the crosslink density (q), and the crosslink efficiency (f) using the Flory–Rehner equation. The average molecular weight between the crosslinks (Mc), 117–2394 for EGDMA and 81-14339 for DEHDMA, found to be increased with pH of the medium, whereas the crosslinking density (q) and crosslink efficiency (f) were decreased for EGDMA and DEGDMA as the pH of the medium was increased (q = 0.03–0.68 for EGDMA and 0.01–0.98 for DEGDMA, whereas f = 51–1056 for EGDMA and 9.9–1760 for DEGDMA). The diffusional exponent (n) values of the synthesized hydrogels were, in general, found to be non-Fickian (0.5 < n < 1). It was concluded that these copolymers demonstrated a sharp change in their media absorbancy and the network parameters with the change in the media pH. This behavior of the hydrogels suggest their strong candidature for being used as oral drug delivery systems targeting the colon part of gastrointestinal tract.