A Copolymer of Monomethoxy Poly(ethylene glycol)‐Polycaprolactone as Form‐Stable Phase Change Materials for Thermal Energy Storage

Abstract In this work, a series of monomethoxy poly(ethylene glycol)‐polycaprolactone (mPEG‐PCL) copolymers with different mass percentages of mPEG was chemically synthesized as form‐stable phase change materials (FSPCMs) for thermal energy storage (TES) application for the first time. Their chemical structures, surface morphology, and thermal properties were studied in terms of nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). 1 H NMR, gel permeation chromatography (GPC), and FTIR results confirmed the successful ring‐opening polymerization of ϵ‐caprolactone with mPEG macromonomer, and the respective average molecular weight of the copolymers was obtained in the range of 9704–17346 g mol −1 . DSC analysis results revealed that the copolymers have a phase change temperature and latent heat in the range of 52.8–57.9 °C and 88.8–114.4 J g −1 respectively and TGA analysis showed that they are thermally stable up to 150 °C. Leakage test results showed that the copolymers (mPEG) x ‐(PCL) y displayed excellent form stability with minimal leakage while thermal cycling revealed good thermal reliability. In addition, the copolymers successfully demonstrated their ability to store and release heat for a prolonged period, making them suitable for TES applications like heating water storage tanks.