One-pot synthesis of photocrosslinked sol–gel hybrid composites containing silver nanoparticles in urethane-acrylic matrixes

The synthesis of new urethane dimethacrylate oligomers based on polytetrahydrofuran (PTHF)/poly(butylene adipate) (PBA): trimethyl-1,6-diisocyanatohexane (TMDI): 2-hydroxyethyl methacrylate (HEMA) (molar ratio 1:2:2) is presented. Organic–inorganic hybrid composites comprising urethane methacrylic macromers and 3-(trimethoxysilyl)propyl methacrylate (MPTS) taken in various gravimetric ratios were prepared by one-pot process through the UV-curing of photopolymerizable mixtures in the presence of 1 wt.% Irgacure 819 photoinitiator, followed by the sol–gel reactions (hydrolysis and condensation) at ambient temperature. Additionally, in some formulations prior obtained silver nanoparticles (AgNPs) were incorporated before photopolymerization. Infrared spectroscopy monitored the microstructural evolution of the silica phase as well as the progress of double bond conversion during photopolymerization, while photo-differential scanning calorimetry (photo-DSC) gave us information on polymerization rate and conversion. The photopolymerization results show that the photopolymerization rates of the hybrid formulations are in the range of 0.084–0.158 s−1, whereas the conversion degree after 5 min of UV irradiation is over 70%. The thermal stability, Young’s modulus and tensile strength of the hybrid films are enhanced with the increase in alkoxysilane content, indicating significant reinforcement of the matrix in the presence of SiOSi linkages. The existence and homogeneous dispersion of nanosilver into the polymer matrix has been supported by EDX and TEM analysis, the last allowing a visualization of the formation of silver nanoparticles with size between 2 and 13 nm (mean diameter 6.3 nm). The four diffraction peaks appeared in the wide angle X-ray scattering spectrum can be assigned to the face-centered cubic silver phase, indicating the formation of metallic silver. The water/ethanol resistance for the hybrid coatings is augmented by the increase of inorganic content.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► One-pot synthesis of photopolymerizable sol–gel/silver hybrid composites is described. ► Photopolymerization give double bond conversions above 70% after 5 min of irradiation. ► Formation of silver plasmon resonance at about 420 nm was evidenced. ► XRD, EDX and TEM analyses proved the homogeneous organic/inorganic distribution. ► The hybrid composites show improved mechanical properties and water/ethanol resistance.