Swelling behaviors, tensile properties and thermodynamic interactions in APS/HEMA copolymeric hydrogels

Abstract

A series of hydrogels was synthesized from hydrophobic allyl phenyl sulfone (APS) and hydrophilic 2-hydroxyethyl methacrylate (HEMA) by bulk free radical copolymerization. The effects of APS content and temperature were studied on network parameters such as effective crosslink density (v_e), molar mass between crosslinks (M_c) and polymer-water interaction parameter (χ) of hydrogels. The increase in APS content was shown to enhance hydrophobic bonding within hydrogel, leading to the decrease in equilibrium water content (EWC) and the increase in volume fraction of polymer in hydrogel (φ₂), tensile strength and Young s modulus. At the same time, the increases in v_e and χ and the decrease in M_c were also observed. When the temperature is increased from 273 to 343 K, the hydrogel A/H3 undergoes decreasing in EWC and increasing in φ₂ and χ values. The thermodynamic analysis indicated that the swelling process is an exothermic process.