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An effective nanofiller-matrix interaction is considered crucial to produce enhanced nanocomposites. Nevertheless, there is lack of experiments focused in the direct measurement of possible filler-matrix covalent linkage, which was the main goal of this work for a carbon nanotube (CNT)/epoxy system. CNT were functionalized with oxygenated (ox) functions and further with triethylenetetramine (TETA). An in-situ determination methodology of epoxy-CNTs heat of reaction was developed by Differential Scanning Calorimetry (DSC). Values of −(8.7 ± 0.4) and −(6.0 ± 0.6) J/g were observed for epoxy with CNT-ox and CNT-TETA, respectively. These results confirm the occurrence of covalent bonds for both functionalized CNTs, a very important information due to the literature generally disregard this possibility for oxygenated functions. The higher value obtained for CNT-ox can be attributed to a not complete amidation and to steric impediments in the CNT-TETA structure. The modified CNTs produced by DSC experiments were then characterized by X-Ray Photoelectron Spectroscopy, Transmission Electron Microscopy and Thermogravimetry, which confirmed the covalent linkage. This characterization methodology can be used to verify the occurrence of covalent bonds in various nanocomposites with a quantitative evaluation, providing data for better understanding of the role of CNT functional groups and for tailoring its interface with polymers.

Smooth and optically transparent titania (TiO2) and TiO2-reduced graphene oxide (RGO) composite films were successfully prepared here. A nanocrystalline anatase suspension was initially prepared by combining the sol-gel process and hydrothermal treatment. Graphene oxide (GO) nanosheets were prepared following a route similar to the Hummers method. Glass slides were then dip-coated using mixtures of TiO2 and GO suspensions. The concentration of GO in the prepared coatings ranged from 1 to 5 wt%. The coated samples were air-dried, and then either calcined or irradiated with UVA light. It was observed that UVA light promoted the reduction of GO to RGO, which increased both the electrical conductivity and hydrophilicity of the composites. The heat treatment of as-prepared coatings also decreased the water contact angle (WCA) with its surface, which is related to the removal of organics residues, graphene burning, and the increase in surface energy. The superhydrophilicity of the prepared samples was investigated after keeping them in air for up to 60 days, followed by UVA illumination. It was also demonstrated that a hydrophilic behavior can be induced in the samples prepared here by applying a direct current (DC) voltage, which could allow their use as smart materials in several applications.

Polystyrene/poly(methylmethacrylate) blends (PS/PMMA) are phase-separated materials and remain so even at elevated temperatures. Blends of PS/PMMA with 40:60, 50:50 and 60:40 wt.% ratio were prepared with PS showing glass transition (Tg) at 64 °C and PMMA at Tg = 119 °C. The constituents were mixed using three different methods: melt-mixing, casting from solution and spin-casting. The thermal properties of the blends were studied using thermogravimetry (TG) and temperature modulated differential scanning calorimetry (TMDSC). Insights into the morphology of phases were obtained by atomic force microscopy (AFM) using intermittent contact mode. The melt-mixing blends have domain sizes larger than a micron and the casting and spin-casting materials are submicron phase-separated. AFM indicated the co-continuous phase arrangement of spin-casting samples at 140 °C. TMDSC showed an increase of interfacial content along with a decrease in the difference between the glass transitions of the phase-separated materials when the preparation varies from melt-mixed to casting.