Silicon-Based Polyurea Composite Coatings with a Hydrogen Bond-Enhanced Network for Improved Mechanical Strength, Transparency, and Solvent Resistance

Abstract

Polyurea materials have attracted considerable attention in fields such as protective coatings and elastomers due to their unique microphase-separated structure and dynamic hydrogen-bonding network. However, achieving high mechanical strength, excellent optical transparency, and environmental resistance simultaneously remains a major challenge for their practical applications. Herein, we report a preparation design strategy based on hydrogen bond-enhanced networks. Through introducing amino-functionalized silica (NH2–SiO2) into a polyurea system constructed from a trifunctional isocyanurate cross-linker, an alicyclic diamine, and a polysiloxane soft segment, and via the formation of high-density C═O···H–N hydrogen bonds between the free amino groups on the NH2–SiO2 surface and the urea carbonyl groups, the filler has been uniformly dispersed in the polymer matrix on the nanoscale, and filler–matrix interfacial defects are effectively eliminated. The as-prepared PU@SiNPs-3 composite coating exhibits outstanding comprehensive performance, with a fracture stress of 14.65 MPa and a toughness of 16.56 MJ/m3, which are 2.1-fold and 3.0-fold higher than those of pristine polyurea, respectively. Meanwhile, it achieves a visible-light transmittance as high as 99.4% at 550 nm, demonstrating excellent optical transparency. Furthermore, the composite coating shows an adhesion strength of 23.4 MPa to glass substrates, excellent flexibility (withstanding a bending radius of 1 mm), and good impact resistance, realizing the synergistic combination of strengthening, toughening, and high transparency. In addition, the dense physical cross-linking network endows the coating with good water and solvent resistance (water absorption less than 3.2% after 168 h, residual mass greater than 96% in various organic solvents). This work, through the precise construction of a noncovalent hydrogen-bond network, effectively addresses the challenges of nanofiller dispersion and interfacial compatibility, providing a facile and versatile design concept for developing advanced polyurea protective coatings.