SiO2/PEG Sol–Gel Hybrid Systems: Study of Morphological Features

In this work, atomic force microscopy (AFM) was used to evaluate the surface roughness of the inorganic–organic SiO2/polyethylene glycol (PEG) hybrid systems, appropriately synthesized via the sol–gel route for applications in the biomedical field, and their nanoscale surface morphology as a function of the different PEG amounts (6, 12, 24, 50 wt.% with respect to the silica content). The aim was to demonstrate the relationship between the surface roughness of the analyzed samples and their porosity. The surface roughness is enhanced with enhanced porosity which creates irregularities and variations on the surface topography and morphology of the rough nanostructured hybrids in which the organic and inorganic phases are bonded together at nanometer to sub-micrometer scales. The results revealed an increase in material porosity as a function of the PEG amount. The nanoscale roughness of the matrix SiO2 is relatively low, as confirmed by the roughness parameters Ra = 2.29 nm and Rq = 4.18 nm. Instead, for all SiO2/PEG hybrids, roughness values greater than those shown by the SiO2 matrix alone, which appear to gradually increase as the weight percentage of PEG increases, were detected. The findings showed that the amount of PEG in the analyzed systems increased the material porosity, underscoring the crucial role that PEG amount plays in compatibilizing the morphological characteristics of blends based on silica. This study opens the door to the realization that improving the sol–gel SiO2/PEG materials' porosity and roughness surfaces can have a variety of effects for various applications.