Synthesis and characterization of poly(ethylene glycol) (PEG) based hyperbranched polyurethanes as thermal energy storage materials

Abstract

In the present work, hyperbranched polyurethanes were prepared by using oligomeric A2+B3 approach. The synthesis of hyperbranched polymers was carried out by reaction of trimethylolpropane (TMP) with poly(ethylene glycol) (PEG) terminated isophorone diisocyanate (IPDI). The prepared hyperbranched polymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (1H NMR). The crystallization properties studied with X-ray diffraction (XRD) and polarized optical microscopy (POM) indicated that hyperbranched polymers had crystalline structure and degree of crystallization reduces with introduction of hard segment. The maximum latent heat of fusion was found to be 145Jg−1 at 55°C. Field emission scanning electron microscopy (FESEM) showed presence of homogeneous structure and thermogravimetric analysis (TGA) results indicated that the materials have good thermal stability. Thermal reliability tests from 20 thermal cycles demonstrate that enthalpy of hyperbranched polyurethanes improves with thermal cycling without any chemical degradation. These materials can be successfully used as polymeric phase change materials for thermal energy storage applications.