Structural Design of P(BMA‐co‐VTES)/TEOS Hybrid Membranes for Removal of Benzene from Water by Pervaporation

Summary: The pervaporation performance of optimized poly(butylmetacrylate‐co‐vinyltriethoxysilane)/tetraethoxysilane (P(BMA‐co‐VTES)/TEOS) hybrid membranes for the removal of benzene from water was investigated. P(BMA‐co‐VTES)/TEOS hybrid membranes prepared by the sol–gel reaction were modified by annealing and trimethylsilylation to enhance the performance of these membranes. The annealing and trimethylmethoxysilane (TMS)‐modifications of P(BMA‐co‐VTES)/TEOS hybrid membranes gave more hydrophobic membranes compared with untreated P(BMA‐co‐VTES)/TEOS hybrid membranes and, consequently, the amount of benzene sorbed in the modified P(BMA‐co‐VTES)/TEOS hybrid membranes increased significantly. When an aqueous solution of dilute benzene was permeated by pervaporation through the annealed and TMS‐modified P(BMA‐co‐VTES)/TEOS hybrid membranes, the annealing treatment enhanced the benzene/water selectivity significantly. This result was attributed to a decrease in residual silanol groups in the annealed hybrid membranes and the formation of an optimum cross‐linked structure of the annealed P(BMA‐co‐VTES)/TEOS hybrid membranes.

Benzene concentration in the permeate for an aqueous solution of benzene through untreated (○) and annealed (•) P(BMA‐co‐VTES)/TEOS hybrid membranes during PV.     

Water/Ethanol Selectivity of New Organic‐Inorganic Hybrid Membranes Fabricated from Poly(vinyl alcohol) and an Oligosilane

To control the swelling of PVA membranes, mixtures of PVA and an inorganic oligosilane were prepared using sol‐gel reactions to yield new PVA/oligosilane hybrid membranes. In the separation of an ethanol/water azeotropic mixture during pervaporation, the effect of the oligosilane content on the water/ethanol selectivity of PVA/oligosilane hybrid membranes was investigated. The water/ethanol selectivity of PVA/oligosilane hybrid membranes was higher than that of PVA membranes, but the water/ethanol selectivity of hybrid membranes decreased with increasing oligosilane content. In order to increase the water/ethanol selectivity, PVA/oligosilane hybrid membranes were annealed. The water/ethanol selectivity of annealed PVA/oligosilane hybrid membranes was greater than un‐annealed hybrid membranes, and significantly governed by the oligosilane content, which could be attributed to both sorption and diffusion selectivities. The relationship between the structure of un‐annealed and annealed PVA/oligosilane hybrid membranes along with permeation and separation characteristics of an ethanol/water azeotropic mixture during pervaporation are discussed in detail.

     

Preparation of Monodisperse Crosslinked Organic‐Inorganic Hybrid Copolymer Particles by Dispersion Polymerization

This study presents a new method for producing monodisperse crosslinked organic‐inorganic hybrid polymer particles in micron‐size by using simple dispersion polymerization. Firstly, highly monodisperse hybrid copolymer particles were prepared by conventional dispersion polymerization of styrene and 3‐(trimethoxysilyl)propyl methacrylate (TMSPM) in a methanol/water medium. It was very interesting to find that slightly crosslinked hybrid polymer particles were formed by this simple dispersion polymerization due to a partial condensation reaction between the adjacent silanol groups of the TMSPM during the polymerization. Secondly, for the hydrolytic condensation of the remaining trimethoxysilyl groups, post treatment by sol‐gel process was carried out to form an inorganic siloxane network, which provides the particle with high crosslinking density. In the proper conditions, monodisperse crosslinked particles could be produced in high TMSPM concentrations, up to 20 wt.‐%. In addition, the size monodispersity of the hybrid polymer particles was maintained after the sol‐gel process. Crosslinking with inorganic networks formed by the sol‐gel process was confirmed by a thermal analysis and a ²⁹Si NMR spectroscopy.

Synthesis of crosslinked organic‐inorganic hybrid polymer particles by dispersion copolymerization and post sol‐gel process.     

Hybrid Organic‐Inorganic Nanostructured Acrylic Films Based on Methacylate Modified Zirconium Oxocluster

Organic‐inorganic nanostructured acrylic films, based on methacrylate‐modified zirconium oxocluster, were prepared by UV‐induced polymerization, which yielded transparent and crack‐free layers. TEM analysis evidenced that all the inorganic particles are well dispersed with no significant macroscopic agglomerations. FT‐IR kinetic investigations showed that the presence of the zirconium oxocluster does not affect the photopolymerization rate or acrylic double bond conversion. An increase on T_g values of the cured films is evident at 15 wt.‐% load of the inorganic filler. A thermal stability increase was also achieved in the presence of the zirconium oxocluster. Surface studies performed by XPS analyses showed the presence of homogeneously distributed zirconium oxoclusters, which induces important improvements of the surface hardness evidenced on the basis of the pencil test.

     

Preparation of a Siloxane Acrylic Functional Siloxane Colloid for UV‐Curable Organic‐Inorganic Hybrid Films

Summary: A new siloxane colloid was developed, for the use in UV‐curable inorganic‐organic hybrid films. The UV‐crosslinkable silica‐colloids were prepared from vinyltrimethoxysilane (VTMS) via a sol‐gel method. The structure of silica‐colloids was characterized using ¹H NMR, ²⁹Si NMR, FT‐IR, and matrix‐assisted laser desorption/ionization (MALDI‐TOF) mass spectrometry (MS). The particle size of the siloxane colloid was evaluated using atomic force microscopy (AFM) and small angle light scattering (SALS). Organic phase was based on an acrylated polyester which was synthesized using 1,4‐cyclohexane dimethanol (1,4‐CHDM), neopentyl glycol (NPG), 1,6‐hexanediol (1,6‐HD), maleic anhydride (MA), adipic acid (ADA), and acrylic acid (AA). The acrylated polyester was characterized by gel‐permeation chromatography (GPC) and acid titration. A photo‐initiator was added to the formulation and the UV‐crosslinking reaction of hybrid film was monitored via photo‐differential scanning calorimetry (Photo‐DSC) and real‐time infrared spectroscopy (RT‐IR). The effect of the concentration of VTMS colloids, UV‐light intensity, and exposure time on the polymerization rate was investigated and compared with an inorganic‐organic hybrid film based on TEOS oligomers. Photo‐DSC and RT‐IR results indicated that VTMS colloids can greatly increase free radical polymerization rate and the VTMS colloids functioned effectively as cross‐linker and reactive diluent. AFM and small angle light scattering (SALS) data showed that the silica‐colloids were well dispersed in the organic phase.

     

Permeation and Separation Characteristics of a Mixture of Benzene/Cyclohexane through Cellulose Alkyl Ester Membranes during Pervaporation

Summary: Cellulose alkyl esters such as ethyl, butyryl, pentyl, and heptyl cellulose with different numbers of carbon in the alkyl ester group were synthesized for the separation of a mixture of benzene/cyclohexane (Bz/Chx = 5/95 w/w) with a low concentration of benzene. All of cellulose alkyl ester membranes showed high benzene/cyclohexane selectivity for a Bz/Chx mixture in pervaporation. With increasing carbon number in the ester groups, the permeation rate increased but the benzene/cyclohexane selectivity decreased. The increase in the permeation rate could be attributed to an increase in the swelling of the membrane due to the feed mixture, and the decrease in the benzene/cyclohexane selectivity was dependent on both the decrease in the solubility selectivity and the diffusion selectivity. These pervaporation characteristics are discussed from the viewpoints of chemical and physical structure of the cellulose alkyl ester membranes such as the degree of swelling, the contact angle, and the density of the cellulose ester membranes, and the solution composition absorbed into their membranes.

Effects of the carbon number of alkyl group in the cellulose alkyl ester membranes on the benzene concentration in the permeate (?) and the permeation rate (○) for the mixture of benzene/cyclohexane during pervaporation.     

Tailored Synthesis and Fundamental Characterization of Organic‐Inorganic Hybrid Gels by Means of a Hydrosilylation Reaction

Summary: Organic‐inorganic hybrid gels have been synthesized from siloxane, 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCTS), tetrakis(dimethylsilyloxy)silane (TDSS) or silsesquioxane, 1,3,5,7,9,11,13,15‐octakis(dimethylsilyloxy)pentacyclo‐[9,5,1,1,1,1]octasilsesquioxane (POSS), as crosslinking reagents and α,ω‐nonconjugated dienes, 1,5‐hexadiene (HD), 1,7‐octadiene (OD) and 1,9‐decadiene (DD), using a hydrosilylation reaction with a Pt catalyst. The network structures of the resulting gels were investigated by means of a novel scanning microscopic light scattering system. The structures of the crosslinking reagent and the length of the α,ω‐non‐conjugated dienes strongly affected the formation and network structures of the resulting gels. The critical gel concentration decreased when the molecular length of the non‐conjugated diene used was increased. The structures and Si? H group numbers of the crosslinking reagents affected the critical gel concentration, and its values decreased in the following order: TDSS > TMCTS > POSS. The mesh size distribution in the network structure was quantitatively characterized using the light scattering system and almost presupposed sizes with quite narrow size distributions were attained in the gels from TMCTS‐HD, OD systems and TDSS‐OD systems. On the other hand, the gels derived from POSS or DD showed larger mesh sizes than expected.

     

Synthesis and Properties of 6FDA‐MDA Copolyimide Membranes: Effects of Diamines and Dianhydrides on Gas Separation and Pervaporation Properties

6FDA‐MDA‐based polyimides were synthesized from a one‐step polycondensation of 6FDA and MDA with other diamines and dianhydrides. The polyimides were characterized by GPC, FT‐IR and NMR, and dense membranes were prepared from their solutions for gas separation and pervaporation. Gas separation and pervaporation properties were investigated using the linear moiety contribution method. The moiety contribution factors were used to analyze the effects of the dianhydride and diamine monomers on gas permselectivity and pervaporation permeation flux. It was shown that the steric effects and flexibility of the monomers and the interactions between the membrane and the penetrants accounted for the differences in separation properties.

     

Selective Removal of Dilute Benzene from Water by Various Cross‐Linked Poly(dimethylsiloxane) Membranes Containing tert‐Butylcalix[4]arene

Summary: This paper focuses on the addition of tert‐butylcalix[4]arene (CA) to cross‐linked poly(dimethylsiloxane) (PDMS) membranes derived from poly(dimethylsiloxane) di(methyl methacrylate) macromonomer (PDMSDMMA) and various divinyl cross‐linker compounds, on the pervaporation characteristics for the removal of dilute benzene from an aqueous solution. When an aqueous solution of 0.05 wt.‐% benzene was permeated through the cross‐linked PDMSDMMA membranes containing CA they showed high benzene/water selectivity and permeability. Both the benzene/water selectivity and permeability of the membranes were enhanced by increasing both the divinyl compound cross‐linker content and the amount of CA, and were significantly influenced by the type of divinyl compound. Addition of CA to PDMSDMMA membranes cross‐linked with divinylperfluorohexane (DVF) showed the best pervaporation performance. The normalized permeation rate, benzene/water separation factor, and pervaporation separation index of these membranes were 1.86 × 10⁻⁵ kg · m/(m² · h), 5 027, and 9 350, respectively. The pervaporation characteristics of the cross‐linked PDMSDMMA membranes containing CA were studied with respect to their chemical and physical structure. Furthermore, the mechanism of the selective permeation of benzene over water through these membranes was investigated.

     

Mesh Size Control of Organic‐Inorganic Hybrid Gels by Means of a Hydrosilylation Co‐Gelation of Siloxane or Silsesquioxane and α, ω‐Non‐Conjugated Dienes

Organic‐inorganic hybrid gels have been synthesized by means of co‐gelation of multi‐functional cyclic siloxane, 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCTS), or cubic silsesquioxane, 1,3,5,7,9,11,13,15‐octakis(dimethylsilyloxy)pentacyclo‐[9,5,1,1,1,1]octasilsesquioxane (POSS), as crosslinking reagents with α,ω‐non‐conjugated dienes, a hexa‐1,5‐diene (HD) and deca‐1,9‐diene (DD) mixture, using hydrosilylation reaction with Pt catalyst. Network structures of the resulting co‐gels have been quantitatively characterized by means of a novel scanning microscopic light scattering system. The feed ratio of HD to DD strongly affects the gelation and mesh size of the co‐gels. The critical concentration of gelation has maximum values in the co‐gelation with a feed ratio of [HD]/[DD] = 1. The mesh‐size of the resulting co‐gels underwent changes with the [HD]/[DD] ratio in the feed, and the structure (geometry) of the crosslinking reagents affect the trend of the mesh size change. The TMCTS‐HD/DD co‐gel obtained with a feed ratio of [HD]/[DD] = 1, showed the minimum mesh size. Whereas the mesh size of the POSS‐HD/DD co‐gel increased with an increase of DD in the feed ratio. The mesh‐size distribution of the co‐gels was narrower than the gels synthesized from single α,ω‐non‐conjugated dienes. Co‐gelation of a TMCT/POSS‐DD system was also investigated, and the critical gelation concentration showed maximum values for the co‐gelation with a feed ratio of [TMCTS]/[POSS] = 1. The mesh size of the co‐gel increased with increasing POSS ratio in the feed.

     

Thiol‐ene Hybrid Organic/Inorganic Nanostructured Coatings Based on Thiol‐Functionalized Zirconium Oxoclusters

The thiol‐functionalized zirconium oxocluster Zr₁₂(µ₃‐O)₈(µ₃‐OH)₈(MP)₂₄ · 4MPA was used as inorganic nanosized building block in the thiol‐ene photopolymerization of APE and TH in a 1:1 molar mixture. Transparent and crack‐free coatings were obtained, and TEM analysis showed that the inorganic particles are well dispersed within the polymeric network with no significant macroscopic agglomeration. An increase of T_g values, storage modulus in the rubbery region, and thermal stability were evidenced by increasing the zirconium oxocluster content in the photocurable formulations. XPS analysis and SIMS depth profile were carried out on UV cured films and showed the presence of a homogeneously distributed zirconium oxocluster.

     

Tunable Nanometer‐Scale Architecture of Organic–Inorganic Hybrid Nanostructured Materials for Structural and Functional Applications

Direct crystallization of polymer crystals along the long axis of carbon nanotubes (CNTs) to produce a hybrid nanostructured material is expected to retain the properties of CNTs and has the advantage of a strong polymer/CNT interface. Three different polymer systems are selected to elucidate the fundamental principles that govern the processing of organic–inorganic hybrid nanostructured materials with nanometer‐scale architecture. The tunable character of the nanometer‐scale hybrid architecture is investigated as a function of undercooling and polymer concentration. It is observed that while polyethylene and nylon 6,6 crystallize in a periodic manner as disk‐shaped crystals along the long axis of the CNTs, the polypropylene–CNTs result in conventional spherulites. The reasons for these differences are analyzed.     

Effective Enzyme Coimmobilization and Synergistic Catalysis on Hierarchically Porous Inorganic/Organic Hybrid Microbeads Fabricated Via Droplet‐Based Microfluidics

In this paper, a novel and robust droplet‐based microfluidic method to fabricate poly(ε‐caprolactone)/silica (PCL/SiO₂) hybrid microbeads with hierarchically porous architecture is described and their performance as multienzyme carriers for cascade catalysis is further investigated in detail. In addition to the precise control on size and monodispersity of PCL/SiO₂ microbeads enabled by the microfluidic method, the presence of ammonia as a catalyst for the hydrolysis and condensation of tetraethylorthosilicate makes it possible to manipulate the competition between sol–gel process and solvent extraction and thus adjust the surface porosity of hybrid microbeads, which eliminates the use of porogens/templates and also the complicated post‐treatment. Isothiocyanate‐immunoglobulin G/cyanine 3‐bovine serum albumin (FITC‐IgG/Cy3‐BSA) and superoxide dismutase/chloramphenicol acetyltransferase (SOD/CAT) are coimmobilized, respectively onto hierarchically porous PCL/SiO₂ hybrid microbeads via either physical adsorption or covalent binding. Fluorescence intensity of coimmobilized FITC‐IgG/Cy3‐BSA proves that the proteins/enzymes immobilization amount via covalent binding is much higher than physical adsorption. The enhanced enzymatic activity, total antioxidant capacity, and reusability assay reveal that coimmobilized SOD/CAT exhibits better performance compared with the mono‐immobilized ones, mainly due to their mutual synergistic effect. The excellent results achieved in the work indicate that hierarchically porous PCL/SiO₂ hybrid microbeads are very promising carriers for multienzymatic catalysis.     

Carboxylic Acid Enriched Porous Organic Polymer as a Platform for Highly Efficient Removal of Methylene Blue from Aqueous Solution

To develop highly efficient organic dyes adsorbents are of great importance for environmental issues. In this work, a negatively charged porous organic polymer (POP) is synthesized by simple aromatic nucleophilic substitution (S_NAr) and hydrolysis reaction. This polymer POP‐TFP‐COOH structure is confirmed by IR and ¹³C cross‐polarization/magic‐angle‐spinning nuclear magnetic resonance. Due to the existence of phenyl rings and carboxylic acid groups, POP‐TFP‐COOH displays excellent adsorption ability for the positive dye methylene blue (MB), with a maximum value of 2740 mg g^?1. This porous polymer can be reused at least four times without obvious loss of its adsorption capacity.     

Acrylate‐Terminated Macromonomers by Michael Addition

A series of diacrylate macromonomers bearing alkoxysilyl units was prepared by convenient Michael addition of aminopropyl methyl diethoxysilane to 1,2‐ethylene glycol diacrylate (EGDA), p‐phenylene diacrylate (PDA) and 1,4‐cyclohexanediol diacrylate (CHDA). The resulting macromonomers have been characterized in detail by NMR spectroscopy, vapor pressure osmometry (VPO) measurements and fast‐atom bombardment mass spectroscopy (FAB‐MS). Average molecular weights M̄_n ranged between 530 and 1 300 g·mol^–1 (VPO). FAB‐MS and size exclusion chromatography (SEC) showed the formation of a homologous macromonomer series. Viscosities of the liquid monomers are relatively low, ranging from 0.082 to 8.30 Pa·s. This renders these compounds interesting as reactive diluents in dental composite formulations. Upon polymerization of the macromonomers, low volumetric shrinkage occurred, which was in the range of ΔV = 2.4 and 3.9 vol.‐% at high conversion. Crosslinking was monitored by photo‐differential scanning calorimetry (photo‐DSC). Furthermore, composites were prepared by mixing 2,2‐bis‐[p‐(2‐hydroxy‐3‐methacryloxypropoxy)‐phenyl]propane (Bis‐GMA) with the new macromonomers, initiator and glass filler. The composites showed compressive strengths up to 244 MPa, flexural strengths from 22 to 42 MPa and Young's moduli between 870 and 3 070 MPa. The composite materials exhibited low volume shrinkage of about 2 vol.‐% in comparison to over 3 vol.‐% shrinkage of commercially available composites.     

One‐Pot Preparation of Core–Shell,Organic–Inorganic,Hybrid Latexes by In Situ Nanoparticle Precipitation in Pickering Emulsion Polymerization

A one‐pot emulsion polymerization process to produce silica nanoparticles fixed on polymer particles is presented. Simultaneous nanoparticle formation/monomer emulsification and later polymerization of monomers prevent the agglomeration of silica particles and result in hybrid organic–inorganic, core–shell latexes. The emulsion polymerization of methyl methacrylate is performed using nascent silica nanoparticles, cetyltrimethylammonium bromide, and ammonium persulfate as Pickering surfactant, cosurfactant, and initiator, respectively. The effects of parameters like temperature, initiator type and concentration, and cosurfactant and silica precursor amounts on the polymerization, coagulation percentage, and morphology of hybrid particles are determined using SEM and TEM.     

Formation of Inorganic/Organic Nanocomposites by Nitroxide‐Mediated Polymerization in Bulk Using a Bimolecular System

Summary: A series of organic‐inorganic nanoparticles were synthesized by nitroxide‐mediated polymerization (NMP) of butyl acrylate initiated by a self‐assembled monolayer of an azo initiator. The azo initiator was immobilized on silica particles in the presence of a stable nitroxide radical, SG1 (an acyclic β‐phosphonylated nitroxide, N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethyl)propyl nitroxide). After preliminary qualitative characterization by X‐ray spectroscopy (XPS) and Fourier‐transform infrared (FTIR) measurements, the nanoparticles were studied by thermogravimetric analysis (TGA) to determine the polymer grafting density and to permit a comparison with corresponding values of the initiator monolayer. It was demonstrated that the grafting from polymerization exhibits a controlled character with a low polydispersity ( < 1.2) in a large range of molecular weights of the grafted chains (from 4 000 up to 145 000 g · mol^?1) under the conditions when the stable radical SG1, acting as chain growth moderator tethered to the inorganic core, was used.

     

Fabrication of Nano‐Sized Hybrid Janus Particles from Strawberry‐Like Hierarchical Composites

Janus nanoparticles possess amphiphilic properties and thus exhibit vast applications in the field of catalysis, drug delivery, displays, and surface/interface stabilizers. Despite several successful approaches, that were developed for micro‐sized Janus particle fabrication, the achievement of nano‐sized Janus particles is still facing challenges due to the difficulty with nanoscale processing. Here, new options for the preparation of Janus nanoparticles are demonstrated from strawberry‐like hierarchical composites with designed surface functional groups for both “satellites” and spherical “core.” The “satellites” of the hierarchical composites can be freely varied, from iron oxide to silica nanoparticles. Results from transmission electron microscopy, fourier transform infrared spectroscopy, and thermal gravimetric analysis measurements clearly prove the successful production of hybrid Janus silica nanoparticles coated by polystyrene and poly(acrylic acid). This technique demonstrates the vast flexibility of the abovementioned technique in terms of size, type, and surface chemistry design of Janus nanoparticles, which thus offers an additional approach to the current synthesis library of hybrid Janus nanoparticles.     

One‐Step Approach for the Preparation of Organic‐Inorganic Janus‐Like Particles by Alkalization of Polystyrene‐block‐Poly(2‐vinylpyridine)/FeCl3 Complex Micelles

A novel approach to organic‐inorganic Janus‐like particles based on the alkalization process of polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) micelles containing FeCl₃ precursors in the P2VP cores in toluene is presented. It is found that by addition of a small amount of NaOH solution to a solution of the spherical PS‐b‐P2VP/FeCl₃ micelles, organic‐inorganic Janus‐like particles with a produced α‐FeOOH domain on one side and PS‐b‐P2VP block copolymers on the other can be prepared. The Janus‐like nanoparticles obtained by this facile approach may have potential application in biomedical areas.     

Organic‐Inorganic Nanohybrids Obtained by Sequential Copolymerization of ε‐Caprolactone and L,L‐Lactide from Activated Clay Surface

Summary: We report here on the controlled grafting of defined copolyester chains directly onto the activated surface of MMT nanoplatelets dispersed in apolar medium. More precisely, monomers such as CL and LA were copolymerized, in dilute solution, by the well‐known coordination‐insertion ring‐opening mechanism initiated directly from the clay platelets. This method is based on the use of MMT organo‐modified by ammonium cations bearing hydroxyl functions. Using a surfactant mixture that contains varying proportions of hydroxyl‐substituted alkyl ammonium and non‐functionalized alkylammonium cations for exchanging the initial Na⁺ counterions of the natural clay allows preparing organoclays with a tunable amount of hydroxyl functions on their surface. These hydroxyl functions can then easily be derivatized into aluminium alkoxides in order to initiate the polymerization directly from the surface of clay swollen in an organic solvent like toluene. The resulting activated organo‐clays proved to promote efficiently the block copolymerization of CL and LA in solution. The results demonstrate that adjusting the parameters allows to control the process. Indeed, the growing copolyester chains are effectively surface‐anchored onto the clay and their average length and grafting density can readily be modulated by the available amount of OH functions on the MMT platelets. These new organic‐inorganic nanohybrid materials present nearly exfoliated morphologies and the grafted copolymers display a semi‐crystalline and blocky structure as attested by DSC and NMR analyses, respectively.

TEM photograph of the recovered nanohybrid based on poly[CL‐block‐LA] diblock copolyester grafted onto Cloisite®30B surface.