Fluoroalkyl End-capped Vinyltrimethoxysilane Oligomer Research Articles

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.

Preparation and applications of fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/chemically modified cellulose fibers composites

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2-CHSi(OMe)3) n-RF: n = 2, 3; RF = CF(CF3)OC3F7: RF-(VM) n-RF] was found to undergo the sol-gel reaction under alkaline conditions in the presence of chemically modified cellulose fibers treated with N-methylglucamine units ( MeGlu) [Cellu-fiber- MeGlu] and treated with iminodiacetic acid units ( ImDia) (Cellu-fiber- ImDia) to provide the corresponding fluorinated oligomeric silica/Cellu-fiber- MeGlu composites [RF-(VM-SiO3/2) n-RF/Cellu-fiber- MeGlu] and /Cellu-fiber- ImDia composites [RF-(VM-SiO3/2) n-RF/Cellu-fiber- ImDia], respectively. Dodecane and water contact angle measurements showed that these obtained composites can supply a superamphiphobic characteristic on their composite powders surface. The RF-(VM-SiO3/2) n-RF/Cellu-fiber- ImDia composites were applied to the packing material for the column chromatography to separate the mixture of hydrocarbon and fluorocarbon oils. In addition, the RF-(VM-SiO3/2) n-RF/Cellu-fiber- ImDia composites were found to have more effective removal ability for fluorinated aromatic compounds than that for the corresponding non-fluorinated ones from aqueous methanol solutions. Interestingly, it was demonstrated that the RF-(VM-SiO3/2) n-RF/Cellu-fiber- MeGlu composite powders are also applicable to the fabrication of liquid marbles, which are millimeter-sized liquids such as water, glycerine, ethylene glycol and dodecane stabilized by the adsorbed composite powders at air-liquid interfaces.

Preparation and applications of wettability-controlled fluoroalkyl end-capped oligomer/cellulose nanofiber composites

Sol-gel reaction of two fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3)n-RF; RF = CF(CF3)OC3F7; n = 2, 3: RF-(VM)n-RF] in the presence of cellulose nanofiber (CNF) under non-catalytic conditions was found to provide the corresponding fluorinated oligomeric silica/CNF composites [RF-(VM-SiO3/2)n-RF/CNF]. The obtained composites were applied to the surface modification of glass to give a good oleophobic/superhydrophobic characteristic on the composite surface due to the fabrication of the roughness architecture. The RF-(VM-SiO3/2)n-RF/CNF composites were also applied to the surface modification of poly(ethylene terephthalate) [PET] fabric swatch, affording a superoleophilic/superhydrophobic characteristic on the modified fabric surface. Modified PET fabric swatch thus obtained was applicable to not only the separation membrane to separate the mixture of oil/water but also the perfect adsorption of oil droplets spread on water interface. In addition, we have prepared the RF-(VM-SiO3/2)n-RF/CNF composites films by casting homogeneous aqueous methanol solutions containing the corresponding composites. Pristine CNF film afforded the superoleophilic property on the surface; however, it was demonstrated that the obtained transparent colorless CNF composite films can supply highly oleophobic characteristic on the surface.

Facile preparation of fluoroalkyl end-capped vinyltrimethoxysilane oligomer/α, ω-dihydroxy-terminated poly(dimethylsiloxane) composite rubber: application to effective removal of fluorinated aromatic compound from aqueous methanol solution by fluoroalkylated silicone composite rubber

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF–(CH2CHSiOMe)3)n–RF; n = 2, 3; RF = CF(CF3)OC3F7: RF–(VM)n–RF] undergoes the sol–gel reactions in the presence of α, ω-dihydroxy-terminated poly(dimethylsiloxane) [HO–(SiMe2O)nH: HPDMS] under non-catalytic conditions to provide the crosslinked RF–(VM)n–RF/HPDMS composite rubber in quantitative isolated yields. Especially, we can isolate the expected composite rubber through the sol–gel reactions, in which the contents of the RF–(VM)n–RF oligomer based on employed oligomer and HPDMS are greater than 0.16%. In contrast, traditional silane coupling agents such as tetraethoxysilane, methyltrimethoxysilane and triethoxy-1H, 1H, 2H, 2H-tridecafluoro-n-octylsilane were unable to afford the expected composite rubber through the sol–gel reactions with HPDMS under similar conditions. The fluoroalkylated silicone composite rubber thus obtained gave no swelling behavior toward water, dimethyl sulfoxide and methanol; however, the composite rubber was found to display the higher swelling characteristic for toluene, hexane and tetrahydrofuran, especially for fluorinated aliphatic solvents. Interestingly, it was demonstrated that the fluoroalkylated silicone composite rubber swollen with hexane can adsorb a variety of aromatic compounds in aqueous methanol solutions. More interestingly, we found that the fluoroalkylated silicone composite rubber can exhibit an excellent adsorption ability toward the fluorinated aromatic compounds such as 2′, 3′, 4′, 5′, 6′-pentafluoroacetophenone, compared to that of the corresponding non-fluorinated one.

Preparation of monolithic fluoroalkyl end-capped vinyltrimethoxysilane oligomer /methyltrimethoxysilane/magnetite composites: Application to selective removal of fluorinated aromatic compounds from aqueous methanol solution under magnetic field

Monolithtic fluoroalkyl end-capped vinyltrimethoxysilane oligomer /methyltrimethoxysilane/magnetite composites [RF-(VM-SiO3/2)n-RF/MeSiO3/2/Mag] were prepared through two simple processes which consist of the sol-gel reaction of the corresponding oligomer [RF-(CH2CHSi(OMe)3)n-RF: n = 2, 3; RF = CF(CF3)OC3F7: RF-(VM)n-RF] with methytrimethoxysilane (MTMS) under acidic conditions, and successively the sol-gel reaction in the presence of magnetic fine particles (Mag) under alkaline conditions. TEM (Transmission Electron Microscopy) pictures show that Mag particles can be effectively encapsulated into fluorinated oligomeric composite cores to produce the expected composites [RF-(VM-SiO3/2)n-RF/MeSiO3/2/Mag]. In addition, field emission scanning electron micrographs (FE-SEM) indicate that the obtained composites consists of monolithic structures to afford an extremely lower bulk specific gravity (0.32 g/cm3); although the corresponding RF-(VM-SiO3/2)n-RF/Mag composites prepared under similar conditions and the RF-(VM-SiO3/2)n-RF oligomeric particles prepared by the sol-gel reaction of the oligomer under alkaline conditions afforded the relatively higher values: 0.68 and 0.50 g/cm3, respectively. The surface wettability of the RF-(VM-SiO3/2)n-RF/MeSiO3/2/Mag composite particles was studied by the dodecane and water contact angle measurements to exhibit a superoleophilic/superhydrophobic characteristic on their surface. Interestingly, these composite particle powders were applied to the facile removal of aromatic compounds such as bisphenol A, bisphenol AF, 4, 4′-biphenol, octafluoro-4, 4′-biphenol, acetophenone, 2′, 3′, 4′, 5′, 6′-pentafluoroacetophenone, trans-cinamic acid and trans-2,3,4,5,6-pentafluorocinamic acid from aqueous methanol solution under a magnetic fields. More interestingly, it was demonstrated that we can observe the more efficient removal ability for the fluorinated aromatic compounds, compared to that of the corresponding non-fluorinated ones. Especially, such monolithic composites were found to provide the higher removal ability for these aromatic compounds than that for the usual RF-(VM-SiO3/2)n-RF/Mag composite powders under similar conditions.

Preparation of fluoroalkyl end-capped vinyltrimethoxysilane oligomer/micro-sized silica composites possessing superoleophilic/superhydrophobic characteristic: application to selective removal of aromatic compounds from aqueous methanol solution by using these composites

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2–CHSi(OMe)3)n-RF; n = 2, 3; RF = fluoroalkyl group: RF-(VM)n-RF] was found to undergo the sol–gel reaction in the presence of micro-sized silica particles under alkaline conditions to afford the corresponding fluorinated oligomer/micro-sized silica composites [RF-(VM-SiO3/2)n-RF/μ-SiO2]. The obtained composites were applied to the surface modification of glass to reveal a superoleophilic/superhydrophobic characteristic on the modified surface. In contrast, fluoroalkyl end-capped vinyltrimethoxysilane oligomer/silica nanocomposites [RF-(VM-SiO3/2)n-RF/n-SiO2], which were prepared in the presence of nanometer-sized silica particles under similar sol–gel reactions, provided an oleophobic/superhydrophobic property on the surface. RF-(VM-SiO3/2)n-RF/μ-SiO2 composites were applied to the solid-phase extraction sorbent to isolate the transparent colorless oil from water-in-oil (W/O) emulsion. These composite powders were also applicable to the effective removal of traditional organic dyes, such as rhodamine B, acid red 289, and fluorescein from aqueous methanol solution. Of particular interest, it was demonstrated that RF-(VM-SiO3/2)n-RF/μ-SiO2 composites, of whose micro-sized silica gel is surface-functionalized with amino units, can exhibit a similar superoleophilic/superhydrophobic characteristic on the composite surface, giving the selective removal of fluorinated phenol-type aromatic compounds from aqueous methanol solutions, although the removal ability for the corresponding non-fluorinated ones was not observed at all under similar conditions.

Amorphous low molecular weight aromatic compounds possessing no weight loss behavior in fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/hexagonal boron nitride nanocomposites even after calcination at 800°C

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3)n-RF; n = 2, 3; RF = CF(CF3)OC3F7] undergoes the sol–gel reactions in the presence of hexagonal boron nitride (h-BN) nanoparticles and low molecular weight aromatic compounds (ArHs) such as bisphenol AF (BPAF) and 1-(2-naphthyl)ethanol (Naph-EtOH) under alkaline conditions at room temperature to afford the corresponding fluorinated oligomeric silica/h-BN/ArHs nanocomposites [RF-(VM-SiO3/2)n-RF/h-BN/ArHs]. TG–DTA analyses and XRD spectra measurements show that the encapsulated ArHs in the fluorinated oligomeric silica/h-BN nanocomposites exhibit an amorphous structure, affording no weight loss corresponding to the contents of the ArHs in the nanocomposites even after calcination at 800°C, although the simple blend hybrids of the RF-(VM-SiO3/2)n-RF/h-BN nanocomposites and the original ArHs provide not only the crystal characteristic toward the ArHs but also a clear weight loss behavior in proportion to the contents of the ArHs in the blend hybrids after calcination at 800°C. 1H MAS NMR spectra, UV–Vis spectra, and fluorescent spectra of the RF-(VM-SiO2)n-RF/h-BN/ArHs nanocomposites obtained through the sol–gel reactions under alkaline conditions showed the presence of the ArHs in the nanocomposites, respectively.

Controlled surface modification of poly(methyl methacrylate) film by fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/hexagonal boron nitride nanocomposites

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3)n-RF; n = 2, 3; RF = CF(CF3)OC3F7] undergoes sol–gel reactions in the presence of hexagonal boron nitride (h-BN) nanoparticles under alkaline or acidic conditions at room temperature to afford the corresponding fluorinated oligomeric silica/h-BN nanocomposites in good isolated yields (~ 80%), respectively. The fluorinated oligomeric silica/h-BN nanocomposites thus obtained were found to exhibit a good dispersibility toward the traditional organic media including water. These two kinds of fluorinated nanocomposites were applied to the surface modification of poly(methyl methacrylate) (PMMA). The fluorinated nanocomposites prepared under alkaline conditions can give not only a good oleophobic characteristic imparted by longer fluoroalkyl groups in the composites but also the higher fluorescent emission related to the presence of h-BN on the only surface side of the modified PMMA film. In contrast, the fluorinated nanocomposites prepared under acidic conditions can provide a good oleophobic characteristic and a higher fluorescent emission on both the surface and even on the reverse side of the PMMA film. Such unique controlled surface modification ability will be discussed by 29Si solid-state NMR spectra of these two types of the nanocomposites. Surface arrangement of the RF-(VM-SiO2)n-RF/h-BN nanocomposites, which were prepared under alkaline or acidic conditions, toward the PMMA film.

Preparation of amphiphobically modified poly(vinyl alcohol) film by fluoroalkyl end-capped vinyltrimethoxysilane oligomer

Hydrophilic poly(vinyl alcohol) (PVA) was chemically modified by using fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(VM)n-RF] to lead the PVA/RF-(VM)n-RF composite films. The PVA/RF-(VM)n-RF composite film obtained under non-catalytic conditions was found to provide the water-soluble property; however, the acidic conditions enabled the composite film to afford no solubility toward water, giving an amphiphobic property on both the surface and reverse sides just after the deposit of an oil or water droplet. RF-(VM)n-RF oligomer was also applied to the fabrication of the PVA/RF-(VM)n-RF/B(OH)3 composite film by using the RF-(VM)n-RF/B(OH)3 nanocomposites, which were prepared by the composite reaction of RF-(VM)n-RF oligomer with boric acid. It was demonstrated that the PVA/RF-(VM)n-RF/B(OH)3 composite film obtained by the interaction of the corresponding nanocomposites with PVA under acidic conditions can afford the perfect water-resistance ability even after immersion of this film into water for 30 min to give the amphiphobic property on both the surface and reverse sides, although the corresponding PVA/RF-(VM)n-RF composite film and the pristine PVA film provided the swelling behavior toward water, respectively. Thermal gravimetric analyses (TGA) and differential thermal analyses (DTA) measurements showed that the PVA/RF-(VM)n-RF/B(OH)3 composite film can give a higher thermal stability than that of the RF-(VM)n-RF/PVA composite film and the pristine PVA film.

Preparation of Fluoroalkyl End-Capped Oligomer/Cyclodextrin Polymer Composites: Development of Fluorinated Composite Material Having a Higher Adsorption Ability toward Organic Molecules

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3)n-RF; RF = CF(CF3)OCF7, n = 2, 3; RF-(VM)n-RF] was applied to the preparation of fluoroalkyl end-capped vinyltrimethoxysilane oligomer/α-, β-, γ-cyclodextrin polymers (α-, β-, γ-CDPs) composites [RF-(VM-SiO2)n-RF/α-, β-, γ-CDPs] by the sol-gel reaction of the corresponding oligomer in the presence of the α-, β-, γ-CDPs under alkaline conditions. The RF-(VM-SiO2)n-RF/α-, β-, γ-CDPs composites thus obtained were found to give a good dispersibility toward the traditional organic media except for water, and were applied to the surface modification of glass to provide a sueperoleophilic/superhydrophobic characteristic on the modified surface, although the corresponding RF-(VM-SiO2)n-RF nanocomposites can give a usual oleophobic/superhydrophobic property on the surface. These composites powders were also found to be applicable to the packing material for the column chromatography to separate the mixture of oil/water and the water in oil (W/O) emulsions. More interestingly, these composite powders were found to have a higher adsorption ability toward not only low-molecular weight aromatic compounds such as bisphenol A and bisphenol AF but also volatile organic compounds, compared to that of the pristine α-, β-, γ-CDPs.

Wettability control between superoleophobic and superoleophilic characteristics on the modified superhydrophobic surfaces treated with fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/poly(styrene-co-butadiene) nanocomposites: application to the separation of oil and water

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3) n -RF; RF = CF(CF3)OC3F7; n = 2, 3: RF-(VM) n -RF] can undergo the sol–gel reaction in the presence of poly(styrene-co-butadiene) (SBR) under alkaline or acidic conditions, respectively, to afford the corresponding fluorinated oligomeric silica/SBR nanocomposites [RF-(VM-SiO2) n -RF/SBR]. Wettability control between superoleophobic and superoleophilic characteristics was observed on the modified superhydrophobic glass surfaces treated with these fluorinated nanocomposites. The nanocomposites, which were prepared under alkaline conditions, can provide a superoleophobic/superhydrophobic (superamphiphobic) characteristic on the modified surface; however, a superoleophilic/superhydrophobic characteristic was observed on the modified surface treated with the fluorinated nanocomposites, which were prepared under acidic conditions. Interestingly, the fluorinated nanocomposite particle powders possessing a superoleophilic/superhydrophobic characteristic were applied to the packing material for the column chromatography to separate not only the mixture of oil and water but also the W/O emulsion to isolate the transparent colorless oil. In addition, these particle powders were found to have a good reusability as the packing materials for the separation of the mixture of oil and water.

Preparation of Fluoroalkyl End-Capped Vinyltrimethoxysilane Oligomeric Silica Nanocomposites Containing Gluconamide Units Possessing Highly Oleophobic/Superhydrophobic, Highly Oleophobic/Superhydrophilic, and Superoleophilic/Superhydrophobic Characteristics on the Modified Surfaces.

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2-CHSi(OMe)3)n-RF (RF-(VM)n-RF)] undergoes the sol-gel reaction in the presence of N-(3-triethoxysilylpropyl)gluconamide [Glu-Si(OEt)3] under alkaline conditions to afford the corresponding fluorinated oligomeric silica nanocomposites containing gluconamide units [RF-(VM-SiO3/2)n-RF/Glu-SiO3/2]. These obtained nanocomposites were applied to the surface modification of glass to provide the unique wettability characteristics such as highly oleophobic/superhydrophobic and highly oleophobic/superhydrophilic on the modified surfaces under a variety of conditions. Such a highly oleophobic/superhydrophobic characteristic was also observed on the modified PET (polyethylene terephthalate) fabric swatch, which was prepared under similar conditions, and this modified PET fabric swatch was applied to the separation membrane for the separation of the mixture of fluorocarbon oil and hydrocarbon oil. The RF-(VM-SiO3/2)n-RF/Glu-SiO3/2 nanocomposites, which were prepared under lower feed amounts of basic catalyst (ammonia), were found to cause gelation in water. Interestingly, it was demonstrated that these gelling nanocomposites are also applied to the surface modification of the PET fabric swatch to give a highly oleophobic/superhydrophobic characteristic on the surface. On the other hand, the modified glass surfaces treated with the corresponding nanocomposite possessing no gelling ability were found to supply the usual hydrophobic characteristic with a highly oleophobic property. More interestingly, the wettability change on the modified PET fabric swatch from highly oleophobic to superoleophilic was observed, and remained superhydrophobic after immersing the modified PET fabric swatch into water.

Preparation of fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/phosphonic acids nanocomposites possessing superoleophobic/superhydrophilic and superoleophilic/superhydrophobic characteristics: application of these nanocomposites to the separation of oil and water

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF–(CH2CHSi(OMe)3) n –RF; RF = fluoroalkyl group; n = 2, 3] can undergo the sol–gel reactions in the presence of a variety of phosphonic acid derivatives such as 1-hydroxyethylidene-1,1-diphosphonic acid, nitrilotris(methylene phosphonic acid), and 2-phosphonobutane-1,2,4-tricarboxylic acid under alkaline conditions to provide the corresponding fluorinated oligomeric silica/phosphonic acids nanocomposites. Interestingly, it was demonstrated that the modified glasses and filter papers treated with these obtained fluorinated nanocomposites can exhibit the superoleophobic/superhydrophilic and superoleophilic/superhydrophobic characteristics on their surfaces, respectively. More interestingly, the modified filter papers treated with these nanocomposites were applied to the separation of the mixture of oil and water.

Preparation of fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/poly(tetrafluoroethylene) nanocomposites possessing a superoleophilic/superhydrophobic characteristic: application to the separation of oil and water

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R F-(CH2CHSi(OMe)3) n -R F; R F = CF(CF3)OC3F7, n = 2, 3: R F-(VM) n -R F oligomer] can undergo the sol–gel reaction in the presence of poly(tetrafluoroethylene) fine particles under alkaline conditions to afford the corresponding fluorinated oligomeric silica/poly(tetrafluoroethylene) nanocomposites [R F-(VM-SiO3/2) n -R F/poly(tetrafluoroethylene) nanocomposites]. Interestingly, the modified glass, poly(tetrafluoroethylene) sheet and filter paper surfaces treated with the obtained nanocomposites were found to exhibit a superoleophilic/superhydrophobic characteristic, although the original poly(tetrafluoroethylene) sheet and the modified glass surface treated with the R F-(VM) n -R F oligomeric silica nanoparticles [R F-(VM-SiO3/2) n -R F] can provide the usual oleophobic/hydrophobic and oleophobic/superhydrophobic properties, respectively. The modified filter paper was applied to the separation membrane for the mixture of oil/water. In addition, the fluorinated poly(tetrafluoroethylene) nanocomposite white-colored powders thus obtained were applied to the packing material for the column chromatography to separate the mixture of oil/water and water-in-oil emulsions. We have also studied on the reusability of the present nanocomposite particle powders as the packing material for the separation of not only the mixture of oil/water but also the water-in-oil emulsions, and the colorless oil was quantitatively isolated under similar conditions even after the use of the packing materials five times.

Preparation and applications of fluoroalkyl end-capped vinyltrimethoxysilane oligomeric nanoparticle ionogels

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF–(CH2–CHSi(OMe)3) n –RF; n = 2, 3; RF = CF(CF3)OC3F7: RF–(VM) n –RF] can undergo the sol–gel reaction under alkaline conditions at room temperature to provide the corresponding fluorinated oligomeric silica nanoparticles [RF–(VM–SiO3/2) n –RF]. Silica nanoparticles and tetraethoxysilane are used to the similar sol–gel reaction to prepare the fluoroalkyl end-capped oligomeric silica nanoparticles [RF–(VM–SiO3/2) n –RF/SiO2]. These obtained two types of fluorinated oligomeric silica nanoparticles cannot afford the gel toward water and traditional organic media such as methanol and ethanol; however, interestingly these fluorinated nanoparticles can cause a gelation in a variety of ionic liquids such as phosphonium, ammonium, pyrazolium, and imidazolium salts-type ionic liquids. These fluorinated oligomeric silica nanoparticles/ionic liquid gels (ionogels) were found to provide a similar ionic conductivity to that of the corresponding parent ionic liquids under a variety of temperatures from 25 to 125 °C, and these fluorinated ionogels can keep the similar ionic conductivity even after 10 h at 125 °C. In addition, these fluorinated oligomeric silica/ionogels are applied to the surface modification of PMMA to exhibit not only surface-active characteristic imparted by longer fluoroalkyl groups, but also a good ionic conductivity related to the ionic liquid on the surface. More interestingly, the modified PMMA film can afford the switching behavior from oleophobic to superhydrophilic characteristics derived from the flip-flop motion between the fluoroalkyl groups and the cationic moieties when the environment on the reverse side is changed from oil to water.

Preparation and Surface Property of Fluoroalkyl End-Capped Vinyltrimethoxysilane Oligomer/Talc Composite-Encapsulated Organic Compounds: Application for the Separation of Oil and Water

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [R(F)-(CH2-CHSi(OMe)3)n-R(F); n = 2, 3; R(F) = CF(CF3)OC3F7 (R(F)-VM oligomer)] can undergo the sol-gel reaction in the presence of talc particles under alkaline conditions at room temperature to provide the corresponding fluorinated oligomeric silica/talc nanocomposites (RF-VM-SiO2/Talc). A variety of guest molecules such as 2-hydroxy-4-methoxybenzophenone (HMB), bisphenol A (BPA), bisphenol AF, 3-(hydroxysilyl)-1-propanesulfonic acid (THSP), and perfluoro-2-methyl-3-oxahexanoic acid (R(F)-COOH) are effectively encapsulated into the R(F)-VM-SiO2/Talc composite cores to afford the corresponding fluorinated nanocomposites-encapsulated these guest molecules. The R(F)-VM-SiO2/Talc composites encapsulated low molecular weight aromatic compounds such as HMB and BPA can exhibit a superoleophilic-superhydrophobic characteristic on the surfaces; however, the R(F)-VM-SiO2/Talc composite-encapsulated THSP and R(F)-COOH exhibit a superoleophobic-superhydrophilic characteristic on the modified surfaces. In these nanocomposites, the R(F)-VM-SiO2/Talc/THSP composites are applicable to the surface modification of polyester fabric, and the modified polyester fabric possessing a superoleophobic-superhydrophilic characteristic on the surface can be used for the membrane for oil (dodecane)/water separation. In addition, the R(F)-VM-SiO2/Talc composites-encapsulated micrometer-size controlled cross-linked polystyrene particles can be also prepared under similar conditions, and the obtained composite white-colored particle powders are applied to the packing material for the column chromatography to separate water-in-oil (W/O) emulsion.

Preparation of magnesium carbonate nanoparticles encapsulated by nanocomposite material derived from fluoroalkyl end-capped vinyltrimethoxysilane oligomer – Application to the surface modification of glass and poly(methyl methacrylate)

Abstract Sol–gel reactions of fluoroalkyl end-capped vinyltrimethoxysilane oligomer in the presence of magnesium carbonate fine particles were found to proceed smoothly under alkaline conditions at room temperature to give the corresponding fluorinated oligomeric silica nanocomposites-encapsulated magnesium carbonate nanoparticles [RF-(VM-SiO2)n-RF/MgCO3]. The obtained composites have good dispersibility in traditional organic media, and these composites are nanoparticles without agglomeration or coagulation before and even after calcination at 800 °C. Parent magnesium carbonate undergoes the decarboxylation at around 400 °C to afford magnesium oxide; however, the more smooth pyrolysis of the RF-(VM-SiO2)n-RF/MgCO3 nanocomposites can be observed at around 300 °C to cause the selective formation of not magnesium oxide but magnesium fluoride. The modified glass surfaces treated with the RF-(VM-SiO2)n-RF/MgCO3 nanocomposites after calcination from 200 to 460 °C were found to exhibit the same superhydrophobic (water contact angle value: 180°) characteristic with good oleophobicity as that of the corresponding nanocomposites before calcination. The transparent colorless modified poly(methyl methacrylate) (PMMA) film was prepared by the treatment of the RF-(VM-SiO2)n-RF/MgCO3 nanocomposites to give the good oleophobicity imparted by fluorine in the composites on the modified surface. RF-(VM-SiO2)n-RF/MgCO3 nanocomposites after calcination at 200–800 °C were also applied to the surface modification of PMMA films, and refractive indices of the obtained transparent colorless PMMA films were found to decrease with increasing the calcination temperatures of the nanocomposites, indicating that magnesium fluoride is likely to form in the composites by increasing the calcination temperatures.

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposites possessing photocatalytic activity even after calcination at 1000 °C

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(VM)n-RF] underwent the sol–gel reaction under alkaline conditions in the presence of anatase titanium oxide nanoparticles (an-TiO2) in tetrahydrofuran to give the corresponding fluorinated oligomer/anatase titanium oxide nanocomposites [RF-(VM-SiO2)n-RF/an-TiO2]. Crystalline structure of an-TiO2 in the nanocomposites thus obtained was found to keep completely its structure without phase transformation to rutile even after calcination at 1000°C, although crystalline structure of the original an-TiO2 nanoparticles underwent a complete phase transformation to the rutile under similar conditions. Interestingly, RF-(VM-SiO2)n-RF/an-TiO2 nanocomposites before and after calcination at 1000°C exhibited the similar photocatalytic activity for the decolorization of methylene blue under UV light irradiation.

Biphenylene units possessing flammable and nonflammable characteristics in fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica gel matrices after calcination at 800 °C

Two kinds of fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(VM)n-RF] silica nanocomposites containing biphenylene units were prepared by the sol-gel reactions of the corresponding oligomer with biphenylene-bridged ethoxysilanes or 4,4′-biphenol under alkaline conditions, respectively. One is the fluorinated oligomer/silica nanocomposites containing biphenylene units [RF-(VM-SiO2)n–RF/Ar-SiO2], of whose biphenylene units were incorporated into nanocomposite cores through the siloxane bondings, and the other is the fluorinated oligomer/silica nanocomposites containing biphenylene units [RF-(VM-SiO2)n–RF/Biphenol], of whose biphenylene units were directly encapsulated into nanocomposite cores through the sol–gel process. Interestingly, the shape of RF-(VM-SiO2)n–RF/Ar-SiO2 nanocomposites is morphologically controlled cubic particles; although the shape of RF-(VM-SiO2)n–RF/Biphenol nanocomposites is spherically fine particles. Thermogravimetric analyses 2H magic-angle spinning nuclear magnetic resonance, Ultraviolet visible, and fluorescent spectra showed that biphenylene units in RF-(VM-SiO2)n–RF/Ar-SiO2 nanocomposites have a flammable characteristic after calcinations at 800 °C; in contrast, biphenylene units in RF-(VM-SiO2)n–RF/Biphenol nanocomposites have a nonflammable characteristic even after calcination at 800 °C. X-ray photoelectron spectroscopy analyses of these two kinds of fluorinated nanocomposites showed that nonflammable characteristic toward biphenylene units in the silica gel matrices is due to the formation of ammonium hexafluorosilicate during the sol–gel process.

UV-induced switching behavior of novel fluoroalkyl end-capped vinyltrimethoxysilane oligomer/titanium oxide nanocomposite between superhydrophobicity and superhydrophilicity with good oleophobicity

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer suffered the sol–gel reaction under alkaline conditions in the presence of titanium oxide nanoparticles in tetrahydrofuran to afford the corresponding fluorinated oligomer/titanium oxide nanocomposites[R F-(VM-SiO 2) n -R F/TiO 2] in excellent to moderate isolated yields. These fluorinated composites thus obtained were nanometer size-controlled fine particles, and exhibited good dispersibility and stability in traditional organic solvents except for water. These fluorinated nanocomposites were applied to the surface modification of glass to exhibit not only a completely superhydrophobic characteristic (a water contact angle: 180°) with a non-wetting property against water droplets but also a good oleophobicity imparted by fluoroalkyl segments in the composites on their surface. Of particular interest, we have found that the wettability for water can be switched between superhydrophobicity and superhydrophilicity by alternation of ultraviolet (UV) irradiation and dark storage with keeping a good oleophobicity on the modified surface treated with the anatase-type titanium oxide composite.