Surface grafting POSS to improve the hydrophobicity and fire safety of polyrotaxane based smart phase change materials

Abstract

Polyethylene Glycol (PEG)-based flexible phase change materials have broad and practical application value in thermal management of flexible electronic devices. Considering the typical application cases and safety of phase change materials (PCMs), in this work, we grafted molecular nanoparticles, POSS, with both hydrophobic and flame retardant functions to the surface of PLR sheets through amidation reaction. The successful grafting of POSS has been fully verified by Fourier-transform infrared spectroscopy, energy dispersive spectroscopy and surface contact angle. The formation of the cross-linked structure and the introduction of POSS make the phase change latent heat of the phase change material slightly decrease from 102.4 J g⁻¹ to 94.4 J g⁻¹, but there is still a high retention rate. It is worth pointing out that the PCMs have excellent shape stability and leakage resistance, cycle stability, and shape memory performance (R_f-99%, R_r-99%). The introduce of cross-linked structure and POSS significantly enhanced the Young’s modulus and tensile strength of the PCM. The surface POSS functionalization endowed the PCM with significantly enhanced hydrophobicity. Specifically, the contact angle of the material was significantly increased from 71° for PLR to 123° for POSS-PLR, and it also had enhanced fire safety with pHRR reduction by 18.4% and THR reduction by 19.1%.