Preparation and properties of a novel form-stable phase change material based on a gelator

Abstract

A series of gelators (Gm, m is the length of the alkyl tails, m = 2, 4, 6, 8, 10, 12, 14, 16 and 18) containing 4,4′-diaminodiphenylmethane moieties were synthesized. The chemical structures of Gm were confirmed by ¹H NMR and MS. The form-stable phase change materials (FSPCMs) were prepared by introducing Gm into paraffin. The minimum gelation concentration (MGC) and gel-to-sol transition temperature (T_GS) properties were tested by the “tube-testing method”. It found that Gm (m = 2, 4, 6) was insoluble in paraffin, while the MGC and T_GS of Gm (m = 8, 10, 12, 14, 16, 18) increased with the increase of alkyl chain. The structure and morphology of the PCMs were systematically investigated by FT-IR, POM, 1D WXAD and SEM. Experimental results revealed that paraffin was restricted because the gelators could self-assemble into three-dimensional netted structures, leading to form the shape-stable PCMs without leakage even above their melting point. The thermal properties were studied by DSC. The research showed that the G18/paraffin FSPCMs exhibited excellent thermal stability and high heat storage density. The shape stability of G18/paraffin was investigated by rheological measurements, indicating that solid ↔ hard gel ↔ soft gel ↔ liquid was observed with the increase of temperature. This work is useful in the comprehensive academic research and industrial application of PCMs.