Abstract:

A serials of hydroxypropyl cellulose esters graft copolymers with different phase change temperature was prepared. In these materials, semi-flexible hydroxypropyl celluloses serve as skeleton, and flexible alkanoic acid molecules serve as functional branch chains. The structures of the copolymers were characterized using FT-IR and NMR techniques. Their phase change properties and crystallization behavior were analyzed by DSC, TGA and X-ray scattering techniques. The results show that the temperatures at which the products absorb or release heat(melting or crystallization of the side chains) increase with the increase of side chain length. The phase change temperature of the materials can be adjusted by varying the length of the side chain. The fusion enthalpy reaches 60 J/g in case palmitic acid, stearic acid and eicosanoic acid are used. Furthermore, it is found that when mixed long-chain alkanoic acids are used as the reactant, the phase change temperatures of the products can be easily adjusted by changing the ratio of components in the mixture. This result are also proven by X-ray scattering results, the d-Spacing of hydroxypropyl cellulose mixed esters falls in between two single hydroxypropyl cellulose esters indicating that an effective grafting of both kinds of alkanoic acids on to the same hydroxypropyl cellulose chains. The results provide a facile method in preparing phase change temperature tunable polymer based solid-state phase change materials within certain temperature range.

Key words: hydroxypropyl cellulose, alkanoic acid, phase change material