High thermal conductivity and excellent flexibility of crystalline polyesters with flexible segments in main chains

Abstract

Thermal conductivity (TC) of polymers can be enhanced by incorporating rigid conjugated structures, which will result in sacrifice of other characteristics such as flexibility. To deal with such problem, a series of polyesters (PEmC) with long methylene units in main chains were synthesized by polycondensation and transesterification. A sharp increment of 219.7% in TC was observed and the maximum TC reached to 0.227 Wm−1 K−1, which is twice that of traditional thermoplastic. It is intriguing that thermal diffusivity for above samples changed few while specific heat capacity of PEmC increased from 0.620 J g−1 K−1 to 1.470 J g−1 K−1 on elongating the length of flexible methylene segments in main chains. Thus TC in this system was mainly enhanced by enhancing specific heat capacity. Due to flexible segments in main chains, Young modulus of PEmC (around 0.2 GPa) is one order of magnitude lower than that of conventional thermoplastic. Moreover, PEmC exhibited good performance both in maintaining flexibility below glass-transition temperature and preserving modulus above glass-transition temperature, which might be remarkable in potential application for flexible electronics.