Performance of silane-coupling agent-treated hydroxyapatite/diethylene glycol-based pH-sensitive biocomposite hydrogels

Abstract

Hydrogels are three-dimensional polymeric networks with segments of hydrophilic groups. Stimuli-responsive hydrogels have played attractive role toward much research due to slight modification of environment by abrupt changes in swelling behavior. In this study, a series of pH-sensitive biocomposite hydrogels were acquired through solvent-free green approach by utilization of diethylene glycol (DEG), citric acid (CA), acrylic acid (AA) and hydroxyapatite (HA). Incorporation of hydroxyapatite (HA) prepared from waste eggshells with ACD resulted in the biocomposite hydrogel (ACD–HA). The synthesized biocomposite hydrogel was examined by various characterization techniques, viz., spectral (FTIR), powder X-ray diffraction (XRD) technique, thermal (TGA and DTG), morphological (SEM) and swelling equilibrium studies. In addition, HA was surface treated with two different silane-based coupling agents, namely 3-aminopropyltrimethoxysilane (AMS) and vinyltriethoxysilane (VES) on the performance properties of biocomposite hydrogels. The results of the studies revealed that VES-treated ACD–HA had superior properties than AMS-treated ACD–HA and untreated ACD–HA on overall properties of biocomposite hydrogels. Hence, the decreasing order of swelling equilibrium behavior in various pH, viz., 4.0, 6.0, 7.4, 8.0, 10.0, has been listed as ACD–HA–VES > ACD–HA–AMS > ACD–HA > ACD. The observations indicated that hydrogels’ adaptability with pH-tuned properties may have greater potential in eco-friendly approaches such as metal ion removal, dye removal and agrochemical release.