Polymer/SiO2 hybrid nanocomposites prepared through the photoinitiator-free UV curing and sol–gel processes

Abstract The polymer/SiO2 nanocomposites were prepared through a dual-curing process involving the UV irradiation in the absence of photoinitiator and the subsequent sol–gel process. The polyester containing β-diketone (PEDK) was firstly synthesized via Michael addition reaction of acetylacetone with 1,6-hexanediol diacrylate, and endcapped with 2-hydroxyethyl acrylate. The PEDK further reacted with isophorone diisocyanate and 3-triethoxysilylpropylamine, giving the polyurethane containing β-diketones (PUDK). The PUDK was then mixed with previously prepared Si-sol, following by UV irradiation and subsequent hydrolysis to obtain the polymer/SiO2 nanocomposites. The molecular structures were confirmed by 1H NMR and FT-IR spectroscopy. The photo-DSC study showed that the photopolymerization reaction was very efficient by the measurements of maximum rate and final unsaturation conversion. The PUDK reacted as a macromolecular photoinitiator under the UV irradiation and a coupling agent in the hydrolysis process. The cured film showed the good transparency even at 60 wt% silicon precursor loading. The SEM analysis indicated the uniformly dispersion of SiO2 in the hybrid film, presenting the evidence of strong connection between the inorganic particles and polymer network. The DMA and TGA results pointed out the enhanced mechanical and thermal properties.