High phase change enthalpy, controllable temperature, and stable shape can expand the application of phase change materials (PCMs) in energy storage. In this study, a series of novel form-stable PCMs with high phase change enthalpy (169-195 J/g) and controllable temperature (45.3-61.4 degrees C) were prepared. The PCMs exhibited a semi-interpenetrating polymer network (semi-IPN) structure resulting from the combination of polyethylene glycol (PEG) and a three-dimensional (3-D) network gel. The gel itself featured an inherent phase change characteristic and a 3-D network structure. Thus, it improved the phase transition enthalpy of the materials and facilitated the formation of a semi-IPN that endowed the materials with excellent form-stable properties. In addition, the latent heat of the composites (169-195 J/g) is much higher than most of the previously reported composites using PEG as phase change component (68-132 J/g). (c) 2017 American Institute of Chemical Engineers AIChE J, 64: 688-696, 2018