Synergistic Interaction of Sulfonyl-Containing Sulfanilamide/Sulfamide To Enhance the Dielectric and Mechanical Properties of Polyurethane Materials

High-performance dielectric materials have gained widespread attention, due to their great potential for various applications, such as flexible electronics and capacitive sensors. In this study, sulfamide (SA) and sulfanilamide (SAN), containing sulfonyl groups, were introduced into polyurethane (PU) as chain extenders. The polyurethane with the best performance was end-capped with 3-methylsulfonyl-1-propanol (3-MSP) to investigate the effects of the SAN/SA molar ratio and the capping agent on the microstructure, dielectric properties, and mechanical performance of the PU. The experimental results indicated that, at a frequency of 102 Hz, the polyurethane material with an SAN/SA molar ratio of 2:1 (sample PU-N2S1) exhibited the highest dielectric constant (15.65), representing a 144% increase, compared to sample PU-N0S0. Meanwhile, sample PU-N2S1 showed the highest degree of microphase separation. At a frequency of 1.26 × 105 Hz, its dielectric loss was 0.055. Notably, 3-MSP had a relatively large dipole moment (μ = 6.93 D). However, its incorporation into polyurethane significantly reduced the dielectric constant. The results demonstrated that the dielectric constant and dielectric loss of polyurethane were not only dependent on its dipole moment but were also closely related to its microstructure, including microphase separation and intermolecular interaction.