Synthesis and properties of in situ prepared polyurethane/PEG-MXene nanocomposites

Abstract

The efficiency of flexible electronic devices based on MXene/polymer composites can be enhanced by careful design of MXenes and polymers and tailored polymer composition for enhanced electrical conductivity, thermal, and mechanical properties. This study describes the production and analysis of novel 2-[methoxy(polyethyleneoxy)6-9propyl]trimethoxysilane (PEG)-silane functionalized MXene and novel polyurethane (PU) nanocomposites with a range of soft segment contents from 30 to 60 wt%. The functionalization of titanium carbide MXene with (PEG) to produce a material with a layered structure was confirmed by Fourier-transform infrared (FTIR) analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), while transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis showed increased MXene nanosheet interlayer spacing after functionalization. After functionalization, the measured mean MXene nanosheet interlayer spacing was 1.57 μm. A series of polyurethane nanocomposites with the addition of 1 wt% PEG-MXene was synthesized in situ using a two-step polyaddition polymerization method. The prepared nanocomposites with intercalated structure had better thermal properties (T_g from 48 to 62 °C and degradation temperature from 278 to 297 °C), mechanical properties (Young's modulus from 8 to 84 MPa and tensile strength from 2 to 11 MPa), and suitable surface characteristics (low roughness coefficient, from 11 to 87 nm and similar to high water contact angle, from 73 to 109°) as compared to pure PU. The addition of PEG-MXene enhanced microphase separation (degree of phase separation from 16.9 to 50.1 %) and strengthened hydrogen bonding (hydrogen bonding index from 38.4 to 66.1 %) in the urethane structure. TEM revealed a 17 nm spacing between PEG-MXene and the PU matrix, and XPS verified the presence of PEG-MXene in PU. Among the novel materials, the nanocomposite with 50 wt% of soft segment content had the most desirable properties with regards to use in flexible electronic devices, i.e., this material had the best thermal, mechanical, and surface characteristics, including the lowest surface roughness (11 nm) and distinct microphase separation.