A series of semi-interpenetrating polymer networks (IPN) of poly(2-hydroxyethyl methacrylate) (poly (HEMA)) and crosslinked polyethylene glycol (PEG) were prepared by simultaneous IPN polymerisation technique. Tetraethyl orthosilicate (TEOS) was used for crosslinking. The prepared semi-IPNs were characterized by Fourier transform infrared spectroscopy (FTIR), C-13-nuclear magnetic resonance (C-13-NMR), X-ray diffraction (XRD), polarized optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), swelling studies and contact angle measurements. The river like pattern of fractured cross section of the SEM micrograph of IPNs indicated no phase separation and also siloxane moiety placement on matrix-air interface. The semi-IPN samples are found to possess crystalline spherulites and the crystallinity reduces as the percentage of poly(HEMA) increases as demonstrated by XRD and POM. Maximum melting enthalpy obtained from DSC thermogram was around 145 J/g. The contact angle studies show that the relative hydrophobicity of the semi-IPNs increases with increase in content of HEMA in the semi-IPNs. These materials show satisfactory latent heat storage capacity and good thermal reliability for application as phase change material (PCM). (C) 2016 Elsevier B.V. All rights reserved.