Fabrication and properties of poly(polyethylene glycol n-alkyl ether vinyl ether)s as polymeric phase change materials

Abstract

A series of poly(polyethylene glycol n-alkyl ether vinyl ether)s (PCmEnVEs) with various lengths of alkyl chains and polyethylene glycol spacers as side chain (m=16,18; n=1,2) were synthesized via two steps. First, monomers-ethylene glycol hexadecyl ether vinyl ether (C16E1VE), ethylene glycol octadecyl ether vinyl ether (C18E1VE), diethylene glycol hexadecyl ether vinyl ether (C16E2VE) and diethylene glycol octadecyl ether vinyl ether (C18E2VE) were synthesized by a modified Williamson etherification. Then, four new types of phase change materials were successfully fabricated by a living cationic polymerization. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) were employed to characterize their composition, thermal properties and crystallization behavior. The results show that, the side chains of PC16E1VE, PC18E1VE, PC16E2VE and PC18E2VE are in a hexagonal lattice, and the onset temperatures for melting of PC16E1VE, PC18E1VE, PC16E2VE and PC18E2VE are 39.8°C, 37.4°C, 51.0°C and 48.9°C, the onset temperatures for crystallization are 36.7°C, 35.2°C, 47.4°C and 46.3°C, respectively. The enthalpy changes of PC18E1VE, PC16E2VE and PC18E2VE are higher than 100J/g; on the contrary, it is 96J/g for PC16E1VE. The enthalpy decrease is no more than 11% after 10 heating and cooling cycles. The 5wt% mass loss temperatures of PC18E1VE, PC16E2VE and PC18E2VE are higher than 300°C; on the contrary, it’s 283°C for PC16E1VE. Using a weak polarity, flexible alkyl ether chain (-OCH2CH2O-) as a spacer to link the main chain and side chain is conducive to the crystallization of the alkyl side chain. These new phase change materials can be applied in heat storage, energy conservation, and environmental protection.