A nonpolar group disulfide bonds driven polyurethane with enhanced dielectric properties

With the growing demand for miniaturized and flexible electronic devices, exploring polymer-based materials with high dielectric properties will play a crucial role in high-energy–density capacitors. In this study, a polyurethane material (PU-S_x) with excellent tensile and dielectric properties was prepared by introducing the aromatic disulfide 2,2'-Diaminodiphenyl disulphide (DTDA). The effect of DTDA content on the dielectric and mechanical properties of PU-S_x was investigated. In the frequency range of 10² Hz to 10⁶ Hz, PU-S_x exhibits a high dielectric constant (> 8.29) and low dielectric loss (< 0.014). With the increase in DTDA content, PU-S_x did not form a conductive network, resulting in a conductivity of only 5.35 × 10^–10 S·m at a frequency of 10^–1 Hz. The presence of two benzene rings and disulfide bonds (S–S) in DTDA significantly enhanced the tensile strength and elongation at break of PU-S_x. The results indicate that, although the disulfide bonds in DTDA are inherently nonpolar, their strong interaction with the hard segments enhances the aggregation tendency of these hard segments, thereby promoting microphase separation to some extent, which leads to an increase in the dielectric constant.