Synthesis and characterization of poly(methyl methacrylate)-boehmite nanocomposites by direct microemulsion polymerization combined with the in-situ sol-gel method

Polymethyl methacrylate - boehmite nanocomposites (PMMA-x-BNCs; where x = 10.0 and 20.0 wt % of PMMA nanoparticles in the latexes) were synthesized by a procedure in two steps. Firstly, polymethyl methacrylate nanoparticles (PMMA-NPs) were prepared either without or with the addition of divinyl benzene as cross-linking agent by semicontinue-direct microemulsion polymerization. Secondly, PMMA-NPs were added to aluminum sec-butoxide solution to obtain PMMA-x-BNCs, by the in-situ sol-gel preparation method. The PMMA-x-BNCs samples were annealed at 300 °C for 4 h and characterized by X-ray diffraction (XRD), electron transmission microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), N2 physisorption, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopies. The PMMA-x-BNCs nanocomposites, mainly those containing cross-linked PMMA-NPs showed enhanced absorption of UV and visible light. The band gap energy (Eg) of PMMA-x-BNCs decreased to a level comparable to that of a semiconductor material. The carbon residues and the remaining carbonyl group of PMMA after the annealing process promoted the improvement of the specific surface area, the decrease in the Eg and the inhibition of the recombination rate of electron-hole pairs. [Display omitted] •PMMA-AlOOH nanocomposites where prepared by microemulsion combined with in-situ sol-gel.•Divinylbenzene was added to PMMA nanoparticles as a cross-linking agent.•PMMA-boehmite nanocomposites showed enhanced absorption of UV and visible light.•Cross-linked PMMA-boehmite nanocomposites promoted the decrease in the band gap energy.•Cross-linked PMMA-AlOOH nanocomposites decreased the recombination rate of (e−, h+) pairs.