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.