Abstract In this work, we presented the synthesis and characterization of poly-melamine-formaldehyde-silica (PMF‑Si) composite from poly-melamine-formaldehyde (PMF) and previously purified commercial sodium silicate used as a precursor of silica nanoparticles (Si‑NPs). The materials were characterized by several physicochemical techniques such as XRD, FTIR, SEM, TEM, AFM, TGA, and DTG analysis to access their properties. We also studied hydrogel dehydration, rehydration, the potential of zero charge (PZC), and the adsorption capacity of the dye methylene blue (MB) in the hydrogel. From XRD analysis, PMF and PMF‑Si materials presented amorphous profiles. AFM, SEM, and TEM images revealed a fibrous PMF structure and homogeneous dispersion of Si-NPs through the PMF-Si composite. The Si‑NPs exhibited an average diameter between 10 to 15 nm. The first PMF-Si hydration reached 93% after synthesis, and complete rehydration is possible up to 70% of dehydration. PMF-Si has the PZC at pH = 1.22 and, at superior values of pH, the composite exhibits superior adsorption rates of MB. The adsorption tests performed to remove MB dye using PMF-Si hydrogel showed a qmax of 140 mg/g, which is superior to other materials routinely used for MB dye removal.

In this report, we studied the thickness effect on the optical and morphological properties of self-assembled (SA) poly(p-phenylenevinylene) (PPV) films, wich were processed with 5 and 75 layers from a PPV precursor polymer and dodecylbenzenesulfonate, and then, thermally converted at 230 °C. The increase of the film thickness yielded more intense peaks in the vibrational spectral range. The electron-phonon coupling was quantified by the Huang - Rhys factor, that shows the effects on the polymer chain mobility in the interface substrate/polymer. A strong emission anisotropy r=0.57 was observed for the film with 5 layers of thickness decreasing to 0.34 for the film with 75 layers. Finally, the surface topology of the films was measured using Atomic Force Microscopy.