Synthesis and characterization of waterborne UV-curable polyurethane nanocomposites based on the macromonomer surface modification of colloidal silica

•A poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) was used to functionalize the aqueous colloidal silica.•The polyurethane nanocomposites were prepared by phase-inversion emulsification method.•The PEGMA modified silica was well dispersed and integrated in the polyurethane films.•The PEGMA modified silica significantly enhanced storage modulus, tensile strength of polyurethane films.

Water-soluble poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) was used to modify aqueous colloidal silica (R301). The PEGMA surface-modified silica (R301-PEGMA) was incorporated into a waterborne UV-curable polyurethane dispersion (WUPU) by phase-inversion emulsification. The R301-PEGMA nanocomposite dispersion exhibited larger particles and lower viscosity than the WUPU/R301 dispersion. The TEM, SEM, and AFM results indicated that the R301-PEGMA was well dispersed and integrated into the WUPU film and its surface. The DMA analysis demonstrated that barely noticeable relaxation tan δ peaks were apparent for 10 wt% R301-PEGMA content, suggesting strong covalent bonding interactions between the WUPU chain and the R301-PEGMA. The R301-PEGMA functions effectively as a multifunctional cross-linker as well as a reinforcing filler and significantly enhances the storage modulus relative to that of the unmodified R301 nanocomposite film. The resulting high-transparency nanocomposite films are promising for a number of applications, including high-performance water-based UV-curable coatings.