Transparent flexible waterborne acrylic nanocomposite coatings for UV-resistant outdoor wood protection

A new class of transparent, flexible, and UV-resistant waterborne acrylic nanocomposite coatings was developed via an in situ emulsion polymerization strategy for exterior wood protection. The base copolymer, poly(2-ethylhexyl acrylate–co–methyl methacrylate), was reinforced with cellulose nanocrystal (CNC) and rutile TiO₂ nanoparticles. The in situ incorporation of the nanofillers within the aqueous polymerization medium enabled homogeneous nanoscale dispersion and enhanced interfacial bonding between the inorganic and organic phases. As a result, the optimized hybrid formulation containing 0.1 wt% CNC and 0.1 wt% TiO₂ (PA2) exhibited a sixfold increase in storage modulus, a + 13.6 °C shift in glass transition temperature, and preserved 73 % optical transmittance at 550 nm. The coatings showed superior UV-shielding efficiency, excellent thermal–mechanical stability, and good film-forming ability with low viscosity. FTIR and FESEM analyses confirmed the uniform distribution and effective integration of nanofillers in the polymer matrix. These findings demonstrate that synergistic CNC/TiO₂ reinforcement via in situ polymerization can yield sustainable and high-performance transparent coatings for wood and related substrates. • Transparent and flexible waterborne acrylic nanocomposite coatings were developed as protective finishes for exterior wood. • Using an in situ emulsion polymerization route promoted uniform nanoparticle distribution and reduced the risk of agglomeration at low filler loadings.