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The objective of this study was to investigate the silica-silane bond formation present at the filler interface of dental composites. Diffuse reflectance infrared Fourier transform spectroscopy was used, and the spectra of pyrogenic silica (Cab-O-Sil) treated with different concentrations of gamma-methacryloxypropyltrimethoxysilane (MPS) were analyzed. The outcome of the study suggested that the gamma-methacryloxypropyltrimethoxysilane (MPS) molecules oriented parallel to the colloidal silica surface (Cab-O-Sil) and formed two types of bonds. One of these bonds was a siloxane bridge formed by a condensation reaction between the silanol groups of both the silica surface and the hydrolyzed silane. Water formed during this reaction and soon became recaptured by the silanol groups of the silica surface. These water molecules were not available for additional hydrolyzation reactions of the unhydrolyzed silane under the experimental conditions. The intensity of the isolated OH-groups decreased because of this reaction. Simultaneous with the condensation reaction, the carbonyl group of the MPS molecule formed hydrogen bonds. This hydrogen bond formation resulted in a peak shift of the carbonyl band from 1718-1720 cm-1 to 1700-1702 cm-1. This hydrogen bond formation also occurred with the isolated OH-groups. After consumption of the isolated OH-groups, no additional surface reaction occurred because no further OH-groups were available for additional condensation reactions or hydrogen bond formation. The findings suggest that the amount of silane needed for filler treatment depends on the number of isolated OH-groups available on the filler surface.

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Developing bionanocomposites from renewable biomass is a viable supplement for materials produced from mineral and fossil fuel resources. In this study, nanocomposites composed of carboxylated cellulose nanocrystals (CCNs) and silver nanoparticles (AgNPs) were prepared and used as bifunctional nanofillers to improve the mechanical and antimicrobial properties of waterborne polyurethane (WPU). Morphology, structure and performance of the CCNs/AgNPs nanocomposites and WPU-based films were investigated. WPU-based composite films were homogeneous and reinforced. The WPU/CCNs/AgNPs composite showed excellent antimicrobial properties in killing both Gram-negative E. coli and Gram-positive S. aureus. The CCNs/AgNPs nanocomposites could be applied as bifunctional nanofillers within WPU.

Synthesis of Ag nanopaticles was carried out with carboxylated cellulose nanocrystals as the scaffolds by reducing metallic cations using NaBH 4 . Ag particles with a size less than 10 nm were readily prepared and dispersed well. The carboxyl and hydroxyl groups of carboxylated cellulose nanocrystals supplied a coordination effect to adsorb metallic cations and Ag nanoparticles, which prevent the aggregation of nanoparticles. The carboxylated cellulose nanocrystals carrying Ag nanoparticles were used as labels for electrical detection of DNA hybridization.