Preparation of Fluoroalkyl End-Capped Oligomers/Hexagonal Boron Nitride Nanocomposites Possessing No Weight Loss Behavior in Nanocomposites Even after Calcination at 800°C

Fluoroalkyl end-capped acrylic acid oligomer [RF-(ACA)n-RF]/hexagonal boron nitride (h-BN) nanocomposites [RF-(ACA)n-RF/h-BN] were prepared by reaction of the corresponding oligomer with h-BN nanoparticles (mean diameter: 50 nm) under non-catalytic or alkaline conditions, respectively. Fluoroalkyl end-capped N,N-dimethylacrylamide oligomer/h-BN nanocomposites [RF-(DMAA)n-RF/h-BN] were also obtained under similar conditions. It was demonstrated that RF-(ACA)n-RF/h-BN nanocomposites, which were prepared under alkaline conditions, afforded a clear weight loss in proportion to the contents of the oligomer in the composites after calcination at 800°C;however, the non-catalytic conditions enabled the RF-(ACA)n-RF/h-BN nanocomposite to give no weight loss behavior corresponding to the contents of the oligomer even after calcination. In fact, it was demonstrated that the RF-(ACA)n-RF/h-BN nanocomposites possessing a clear weight loss property could afford the fluorescent peak around 370 nm related to h-BN in the composites;however, the same fluorescent intensity of this nanocomposite after calcination at 800°C as that of the original h-BN was observed, indicating that this nanocomposite could give a clear weigh loss behavior corresponding to the content of the oligomer during the calcination process. In contrast, the RF-(ACA)n-RF/h-BN nanocomposites possessing no weigh loss behavior were found to exhibit the similar fluorescent intensity before and even after calcination at 800°C, suggesting that the corresponding nanocomposites could provide no weight loss ability corresponding to the contents of the oligomer in the composites even after calcination. Similarly, RF-(DMAA)n-RF/h-BN nanocomposites, which were prepared under non-catalytic or alkaline conditions, were found to provide no weight loss corresponding to the contents of the oligomer even after calcination, respectively. These fluorinated h-BN nanocomposites were applied to the surface modification of PMMA [poly(methyl methacrylate)] to exhibit an oleophobic property on the modified PMMA surface. RF-(ACA)n-RF/h-BN nanocomposites possessing a clear weight loss behavior, whose composites were calcinated at 800°C, afforded not oleophobic but oleophilic property on the modified PMMA surface, quite similar to that of the pristine PMMA film surface;however, more interestingly, we found that RF-(ACA)n-RF/ and RF-(DMAA)n-RF/h-BN nanocomposites possessing no weight loss characteristic, whose composites were calcined at 800°C, could supply a good oleophobic property related to the fluoroalkyl segments in the composites on the modified PMMA surfaces, respectively.

Facile Preparation of Fluoroalkyl End-Capped Vinyltrimethoxysilane Oligomer/Sand Composites Possessing Superoleophilic/Superhydrophobic Characteristic: Application to Oil/Water Separation and Selective Removal of Fluorinated Aromatic Compounds from Aqueous Methanol Solution

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2-CHSi(OMe)3)n-RF: n = 2, 3, RF = CF(CF3)OC3F7: RF-(VM)n-RF], was applied to the facile preparation of the corresponding oligomer/sand (Ottawa sand: OS) composites [RF-(VM-SiO3/2)n-RF/OS] through the sol-gel reaction of the oligomer in the presence of micro-sized OS particles (590 - 840 μm) under alkaline conditions at room temperature. FE-SEM (Field Emission Scanning Electron Micrograph) images showed that the obtained composites consist of the RF-(VM-SiO3/2)n-RF oligomeric nanoparticles and the micro-sized OS particles. Interestingly, the RF-(VM-SiO3/2)n-RF/OS composites thus obtained can provide the superoleophilic/superhydrophobic characteristic on the composite surface, applying to the separation of not only the mixture of oil/water but also the W/O emulsion to isolate the transparent colorless oil. The fluorinated oligomeric OS composites were also found to be applicable to the selective removal of fluorinated aromatic compounds from an aqueous methanol solution. Especially, it was demonstrated that the fluorinated OS composites can supply a higher efficient and smooth separation ability for the separation of the mixture of oil and water than that of the corresponding fluorinated micro-sized controlled silica gel (μ-SiO2) composites (average particle size: 9.5 μm), which were prepared under similar conditions. In addition to the separation of oil/water, the fluorinated OS composites provided higher and more selective removal ability for the fluorinated aromatic compounds from aqueous solutions than that of the μ-SiO2 composites.