Surface treatment of TiO2nanoparticles via sol–gel method: effect of silane type on hydrophobicity of the nanoparticles

Hydrophobic TiO nanoparticles are important elements in preparation of functional organic coatings. In fact, hydrophobicity of the nanoparticle helps to optimize the photoactivity of the coating while maintaining its durability. In this study, surface treatment of the commercial TiO nanoparticles was carried out using various silane precursors via sol-gel method in both acidic (pH 2) and alkaline media (pH 12). A long aliphatic chain (F1), a short aliphatic chain (F2), and an aromatic (F3) fluorosilane were used for this purpose. The treated nanoparticles were characterized using Fourier transform infrared and X-ray photoelectron spectroscopy, thermal gravimetric analysis, and transmission electron microscopy. Hydrophobicity of the treated nanoparticles was evaluated by floating in de-ionized water. The results showed that the adsorption of F1 on TiO only takes place in the alkaline condition while F3 is adsorbed in both alkaline and acidic conditions. Furthermore, no significant adsorption for F2 was detected neither in alkaline nor acidic conditions. The floatation results revealed a hydrophobic nature for F1 and F3 treated nanoparticles, however, nanoparticles attempted with F2, remained hydrophilic. It was concluded that the hydrophobicity of the nanoparticles is affected by both chemical nature of fluorosilane as well as pH of the treatment media

Surface Modification of Silica Nanoparticles with Titanium Tetraisopropoxide and Evaluation of their Photocatalytic Activity

Silica nanoparticles were modified with titanium tetraisopropoxide (TTIP) via atwo-step sol-gel route. The modified silica nanoparticles were characterized using FTIR spectroscopy, thermal gravimetric analysis (TGA) and EDAX elemental analysis. Photocatalytic activity of the modified nanocomposites was evaluated by photo-activated degradation of Rhodamine B (Rh.B) dyestuff, as a colorant model, in distilled water. Reduction in Rh.B concentration in aqueous solution was evaluated by UV-visible spectroscopy and with the aid of visual observations. The FTIR spectroscopy results confirmed the formation of Ti-O-Si chemical bond on the surfaceof silica nanoparticles. TGA test results showed that the weight loss of the modified sample is due to deterioration of the alkoxy groups of the SiO2 surface. According to the results of EDAX elemental analysis, the presence of carbon and titanium in the structure of the modified samples and also reduction in oxygen levels are attributed to the chemical interactions due to surface chemical modification. Carbon detection in the composition can be attributed to the presence of isopropoxide in titanium tetraisopropoxide compound. The results also revealed that, with TiO2 grafting on the silica nanoparticles surface, absorption in UV region is increased and that the silica nanoparticles modified with titanate compound show photocatalytic characteristics and degradation ability of Rh.B dyestuff under UV light irradiation. It became also evident that the photocatalytic activity of the modified nanoparticles is less than TiO2 nanoparticles. However, by inclusion of modified silica nanoparticles into the polymeric coating, the photocatalytic properties of the coating can be established. Although modified silica nanoparticles have less photocatalytic activity compared to TiO2 nanoparticles, but they cause less damage to the polymer matrix

Design and Characterization of Novel Potentially Biodegradable Triple-Shape Memory Polymers Based on Immiscible Poly(l-lactide)/Poly(ɛ-caprolactone) Blends

In this study, covalently cross-linked network strategy has been applied to prepare new triple-shape memory polymers (TSPs) based on poly(l-lactide) (PLA)/poly(ɛ-caprolactone) (PCL) blends. The TSPs were fabricated by adding di-cumyl peroxide, with triallyl isocyanurate as a coagent for performing the cross-linking reaction. The differential scanning calorimetry (DSC) analysis demonstrated that all the PLA/PCL blends show two melting points (T m,PCL and T m,PLA ), which can be employed as the transition temperature (T trans ) to induce triple-shape memory behavior. The scanning electron microscopy (SEM) analysis indicated that there are two immiscible morphologies: co-continuous structure and matrix-droplet. The influence of temperature on the crystalline phase changes was analyzed by X-ray diffraction at various temperatures. The results revealed that during the heating–cooling cycle, the degree of crystallinity decreased when the temperature increased and at higher temperature, the crystallization peaks of PCL disappeared. Multiple thermal–mechanical tests were performed and the results showed that the composition ratio of the two phases plays an important role in the triple-shape memory behavior. The results confirmed that the excellent shape memory behavior was obtained for the sample containing 50 wt% PCL

Nanocomposites based on poly(L-lactide)/poly(epsilon-caprolactone) blends with triple-shape memory behavior: Effect of the incorporation of graphene nanoplatelets (GNps)

In this study, a novel thermally actuated triple-shape memory polymer (triple-SMP) based on poly(L-lactide) (PLA)/poly(ε-caprolactone) (PCL)/graphene nanoplatelets (GNps) nanocomposite was prepared by facile solution mixing method and the design of which was based on two well-separated melting temperatures. In order to improve the dispersion of GNps in the matrix, functionalization reactions were carried out on the GNPs surface. Functionalization was confirmed by various techniques including FTIR, Raman and TGA analysis. TEM micrographs revealed an exfoliated morphology for the functionalized GNps (FGNps) and a homogenous dispersion in the matrix. The crystallinity behaviour of nanocomposites was investigated by DSC and variable temperature XRD (VT-XRD) analysis and an increase in crystallinity was observed. Dynamic mechanical analysis (DMA) showed that the presence of FGNps improves the fixity and recovery ratios because of increase in crystallinity and thermal conductivity. The best shape memory behavior was obtained for PLA50/PCL50/FGNp 1.5 nanocomposite