Film forming hybrid acrylic/ZnO latexes with excellent UV absorption capacity

Abstract

Acrylic/ZnO hybrid latexes were synthesized through a two-step emulsion polymerization process. First, a hybrid seed was synthesized by miniemulsion polymerization, which contained all the hydrophobically modified ZnO nanoparticles. Subsequently, this hybrid seed was employed in a seeded semibatch emulsion copolymerization yielding high solids content hybrid latexes (40 wt%). Cryo-transmission electron microscopy (cryo-TEM) demonstrated that the dispersion of the ZnO nanoparticles in the initial miniemulsion was not homogeneous, which led to a hybrid seed with two populations, polymer particles containing ZnO and pristine polymer particles. After the second step of polymerization barely the same morphology was obtained. Nevertheless, it was proved by electron tomography (3D-TEM) that the ZnO nanoparticles were encapsulated in the polymer particles. The hybrid films containing ZnO presented a superior UV absorption capacity than their counterpart hybrid acrylic/CeO2 prepared following the same strategy.