Abstract Carbon nanostructures have been extensively studied due to combination of properties they present. With different geometries and reactivities, carbon nanotubes, graphene and fullerene were oxidized and modified with octadecylamine (ODA) in order to decrease van der Waals’s interaction and consequently improve the polymer-carbon nanostructures affinity for use in nanocomposites. Nanostructures were characterized as morphology, chemical structure, molecular conformation and thermal properties. All nanostructures showed results that confirm the modification with ODA, without geometry being altered. Modified nanostructures showed different percentages of ODA: graphene 86%, carbon nanotubes 83% and fullerene 63%. It was attributed to distinct reactivities, shapes and specific surface area available, due to different amounts of reactive terminals obtained before oxidation reactions. However, they showed a lower interfacial interaction, which is highly favorable for use in polymer nanocomposites.

Abstract The aim of the present work was the obtaining and characterization of dental hybrid composites using nanoparticles (clay or silica) and boron-aluminum-silicate microparticles. We evaluated the dispersion of the nanofillers when changing their loading among 2.5%, 5%, 10% and 25% wt. Were tested, in the above quantities, four different types of nanofillers, two nanosilicas and two nanoclays The remainder of the inorganic phase, up to a total loading of 75% wt, was given by the boron-aluminum-silicate microparticles. The systems were characterized by XRD, TGA, LF-NMR, and . FTIR was used to determine the degree of conversion. The XRD and LF-NMR showed that the composites with 2.5% of clays, contained an exfoliated profile, and the groups with higher amounts of clay showed intercalated areas or the agglomeration of these particles. Furthermore, the silicas were agglomerated in all groups. The thermal resistance of the material was not affected by the silicas, but improved when using 2.5% of nanoclays. On the other hand, the addition of these particles caused the reduction of the degree of conversion of the systems.

The aim of this study was to obtaining an adhesive made of dimethacrylate copolymer and clay particles in different concentrations. The samples were prepared by light curing and were evaluated by XRD, FTIR and TGA as well as by measuring flexural strength, elasticity modulus and tensile resistance. The XRD and the mechanical test results indicated that the system with 0.2% clay is exfoliated, while the highest concentrations showed the agglomeration of these clays. FTIR was used to determine the conversion, and showed that use of clays particles are unable to significantly alter the polymerization until 1.0%. However, for the group containing 1.5%, there was a decline in this index. In the thermogravimetric analysis, only the groups with 0.2% of clays showed increased thermal resistance. In conclusion, the incorporation of clay at 0.2% concentration produces a well-dispersed system and can be applied as a dental adhesive.

We investigated the effect of adding titanium dioxide nanoparticles (TiO2) to ethylene vinyl acetate (EVA) copolymer, containing 28% vinyl acetate groups, on the crystallinity and miscibility of the copolymer. Films of EVA/TiO2 containing 0.25%-1% TiO2, relative to the total weight of EVA, were prepared from their solution. The obtained films were characterized by X-ray diffraction, low-field nuclear magnetic resonance, and differential scanning calorimetry. The addition of TiO2 to the EVA copolymer was proved to cause changes in the crystallinity and mobility of the polymer chains of EVA, due to new intermolecular interactions and nanostructure organization.

Poly (ε-caprolactone) (PCL) based hybrids containing different amounts of modified (Aerosil® R972) and unmodified (Aerosil® A200) silica oxide were prepared employing the solution method, using chloroform. The relationships of the amount of nanofillers, organic coating, molecular structure and intermolecular interaction of the hybrid materials were investigated mainly using low-field nuclear magnetic resonance (NMR). The NMR analyses involved the hydrogen spin-lattice relaxation time (T1H) and hydrogen spin-lattice relaxation time in the rotating frame (T1ρH). The spin-lattice relaxation time measurements revealed that the PCL/silica oxide hybrids were heterogeneous, meaning their components were well dispersed. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also employed. The DSC data showed that all the materials had lower crystallization temperature (Tc) and melting temperature (Tm), so the crystallinity degree of the PCL decreased in the hybrids. The TGA analysis demonstrated that the addition of modified and unmodified silica oxide does not cause considerable changes to PCL's thermal stability, since no significant variations in the maximum temperature (Tmax) were observed in relation to the neat polymer.