Organosiloxane Network Research Articles

Polybenzimidazole Membrane Crosslinked with Epoxy-Containing Inorganic Networks for Organic Solvent Nanofiltration and Aqueous Nanofiltration under Extreme Basic Conditions.

In this study, a novel polybenzimidazole (PBI)-based organic solvent nanofiltration (OSN) membrane possessing excellent stability under high pH condition was developed. To improve the chemical stability, the pristine PBI membrane was crosslinked with a silane precursor containing an epoxy end group. In detail, hydrolysis and condensation reaction of methoxysilane in the 3-glycidyloxypropyl trimethoxysilane (GPTMS) yields organic–inorganic networks within the PBI membrane structure. At the same time, the epoxy end groups on the organosiloxane network (Si–O–Si) reacted with amine groups of PBI to complete the crosslinking. The resulting crosslinked PBI membrane exhibited a good stability upon exposure to organic solvents and was not decomposed even in basic solution (pH 13). Our membrane showed an ethanol permeance of 27.74 LMHbar−1 together with a high eosin Y rejection of >90% under 10 bar operation pressure at room temperature. Furthermore, our PBI membrane was found to be operational even under an extremely basic condition, although the effective pore size was slightly enlarged due to the pore swelling effect. The results suggest that our membrane is a promising candidate for OSN application under basic conditions.

Toughened polymer electrolyte membranes composed of sulfonated poly(arylene ether ketone) block copolymer and organosiloxane network for fuel cell

The semi-interpenetrating polymer network (semi-IPN) based electrolyte membrane was synthesized from the poly(arylene ether ketone)-b-ketone sulfonated poly(arylene ether ketone) multi-block copolymer (PAEK-b-KSPAEK) and the organosiloxane organic-inorganic hybrid polymer network (OSPN) pre-synthesized. The chemical structure of the synthesized PAEK-b-KSPAEK and semi-IPN was identified using 1H and 19F nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy, and the dimension of the phase separated ionic clusters was examined by small angle X-ray scattering spectroscopy. Introduction of OSPN to PAEK-b-KSPAEK improved not only the thermal and mechanical stability (toughness) but also the oxidative stability. The performance of the membrane electrode assembly fabricated with the semi-IPN electrolyte membranes was superior to that of the pure block copolymer membrane because of the enhanced proton conductivity and toughness. While the semi-IPN24 membrane showed the comparable proton conductivity and cell performance to Nafion 115 membrane, its methanol permeability was significantly lower than that of Nafion 115 membrane.

Synthesis and characterization of nano‐modified permeability membrane

Novel high‐flux and fouling‐resistant pervaporation membranes were synthesized. The nano‐SiO2/polyurethane acrylate (NPUSA) membrane was prepared by 2,4‐toluene diisocyanate, hydroxy alkyl silicone oil (Tech‐2120), and hydroxyethyl acrylate and cross‐linked with the monomer pentaerythritol triacrylate (PETA) by UV curing technology. Nano‐SiO2, which has a large amount of hydroxyl groups that can make a reaction with the isocyanato (NCO), was used as a cross‐linking agent as well as an inorganic silicone precursor to generate an inorganic network. An inorganic organosiloxane network (SiOSi) was generated in the membrane by the electrophilic addition of carbamate between hydroxyl groups and isocyanato. The impact of nano‐SiO2 to NPUSA membrane was investigated using Fourier transform infrared spectrometer (FTIR), gel permeation chromatography, thermal gravimetric analysis, and atomic force microscopy (AFM). FTIR analysis confirmed the presence of the SiOSi network in the membrane, and AFM analysis confirmed the homogeneous distribution of this network throughout the membrane. The performance of NPUSA/PETA membrane was also compared with the commercially available membranes poly(vinyl alcohol)/poly(acrylonitrile) and polydimethylsiloxane and was found to be more resistant to compaction and with better permeability. Copyright © 2015 John Wiley & Sons, Ltd.

Facile and Versatile Platform Approach for the Synthesis of Submicrometer-Sized Hybrid Particles with Programmable Size, Composition, and Architecture Comprising Organosiloxanes and/or Organosilsesquioxanes

We present a facile and versatile platform approach for the synthesis of submicrometer-sized hybrid particles based on an oil-in-water emulsion. These particles comprise organosiloxanes and/or organosilsesquioxanes formed via hydrolysis and polycondensation of alkyl- or aryltrimethoxysilane, and polystyrene or poly(methyl methacrylate) formed through radical polymerization of styrene and methyl methacrylate, respectively. In this synthesis, the alkyl- or aryltrimethoxysilane fulfills three different roles: (i) it is part of the oil phase, (ii) serves as monomer for the formation of the organosiloxane network, and (iii) forms a surface active species that stabilizes the emulsion. Size, composition and architecture of the resulting hybrid particles are programmable in this synthetic approach, as demonstrated for the combination phenyltrimethoxysilane/styrene. The versatility of the approach is demonstrated by preparing hybrid particles based on following precursor/monomer combinations: phenyltrimethoxysilane/methyl methacrylate, methyltrimethoxysilane/styrene, (3-acryloxypropyl)-trimethoxysilane/styrene and (3-mercaptopropyl)trimethoxysilane/styrene. Latter combination yields hybrid spheres with thiol groups suited for further functionalization.

Mixed matrix membranes for organic solvent nanofiltration

Polyimide (PI) (P84) based organic solvent nanofiltration (OSN) membranes are well documented in the literature. One drawback of P84 based OSN membranes is the decline in the flux performance over time and with pressure. This is attributed to the compaction of the membrane top layer. The present work introduces novel P84 based OSN membranes which overcome the problem of compaction by incorporating an organic–inorganic hybrid network within the membrane matrix. The inorganic network also acts as a crosslinking agent for the polyimide. 3-Aminopropyl trimethoxysilane (APTMS) was used as a crosslinking agent as well as an organosilicone precursor to generate an inorganic network. An inorganic organosiloxane network (Si–O–Si) was generated in the membrane by hydrolysis and condensation of methoxysilane in APTMS. The impact of APTMS on the resulting PI membranes was investigated using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), water contact angle and energy diffracted X-ray (EDX). FTIR analysis confirmed the presence of the Si–O–Si network in the membrane and EDX analysis confirmed the homogeneous distribution of this network throughout the membrane including in the thin separation layer. Nanofiltration performance of these membranes was evaluated in solvents such as acetone, dimethylformamide (DMF) and dichloromethane (DCM). Flux profiles showed a great improvement in terms of resistance to compaction after treating with this organic–inorganic based crosslinker, although the inorganic network reduced the flux. After treatment with APTMS, membranes increased in rigidity and strength, and there was no swelling even in high swelling solvents such as DCM. Addition of maleic acid to the dope solution provided an improvement in the flux of the crosslinked membrane. The flux could be also manipulated by varying the crosslinking conditions. Nanofiltration (NF) performance of the mixed matrix membrane (MMM) was compared with the commercially available membrane Duramem™300 in different solvents, and was found to be more resistant to compaction but with lower flux as compared to Duramem™. The performance of MMM was also compared with Duramem™200 for a case study of active pharmaceutical ingredient (API) purification.

Proton-conducting electrolyte membranes based on organosiloxane network/sulfonated poly(ether ether ketone) interpenetrating polymer networks embedding sulfonated mesoporous benzene–silica

Composite membranes based on organosiloxane network (OSPN)/sulfonated poly(ether ether ketone) (SPEEK) interpenetrating polymer network (IPN) structures with sulfonated mesoporous benzene–silica (SMBS) proton conductors embedded are fabricated. The flexibility and toughness properties of OSPN are expected to compensate for the brittleness of the sPEEK membranes. The 2D-hexagonal cylindrical mesopore structures of SMBS maintain the water content at a high level to enhance the conductivity, even at low relative humidity. Compared to the pristine sPEEK membranes, the ternary composite membranes can endure about 10 times more elongation before breaking. Both OSPN and SMBS components enhance the proton conductivity of sPEEK membranes in a hydrated state, while maintaining the water uptake at below 55% even at temperatures as high as 100 °C. The SAXS patterns of the composite membranes explain the water-related membrane properties of composite membranes. The maximum power densities of Nafion membrane-based MEAs are 178.4 mA cm−2, 132.2 mA cm−2, and 90.9 mA cm−2, but those of composite membrane-based ones are 159.1 mA cm−2, 134.2 mA cm−2, and 110.8 mA cm−2 at 95%, 70%, and 45% relative humidity, respectively.

Preparation of inorganic–organic hybrid proton exchange membrane with chemically bound hydroxyethane diphosphonic acid

AbstractProton‐conductive inorganic–organic hybrid intermediate‐temperature membranes were prepared from 3‐glycidoxypropyltrimethoxysilane (GPTMS) and 1‐hydroxyethane‐1,1‐diphosphonic acid (HEDPA) by sol–gel process. To prevent the leaching out of phosphonic acid, triethylamine was used as catalyst to promote the reaction of HEDPA and GPTMS to immobilize phosphonic acid groups. Fourier transform infrared spectra revealed that phosphonic acid groups of HEDPA were chemically bounded to organosiloxane network as a result of the reaction of POH of HEDPA and epoxy ring of GPTMS. TG‐DSC results indicated that the hybrid membranes were thermally stable up to 250°C. The proton conductivity of the hybrid membranes increased with temperature from 30 to 130°C. The proton conductivity of hybrid membrane with the molar ratio of GPTMS/HEDPA = 2/1 can reach up to 1.0 × 10−3 S/cm under anhydrous condition at 130°C, which reveals that this membrane is a promising proton exchange membrane for intermediate‐temperature proton exchange membrane fuel cell. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Semi-interpenetrating polymer network electrolyte membranes composed of sulfonated poly(ether ether ketone) and organosiloxane-based hybrid network

A semi-interpenetrating polymer network (semi-IPN) proton exchange membrane is prepared from the sulfonated poly(ether ether ketone) (sPEEK) and organosiloxane-based organic/inorganic hybrid network (organosiloxane network). The organosiloxane network is synthesized from 3-glycidyloxypropyltrimethoxysiane and 1-hydroxyethane-1,1-diphosphonic acid. The semi-IPN membranes prepared were stable up to 300 °C without any degradation. The methanol permeability is much lower than Nafion ® 117 under addition of the organosiloxane network. The proton conductivity of semi-IPN membranes increases with an increase the organosiloxane network content; the membrane containing the 20–24 wt% organosiloxane network shows higher conductivity than Nafion ® 117. The power density of the MEA fabricated with the semi-IPN membrane with 24 wt% organosiloxane network is 135 mW cm −2, much better than that of the pristine sPEEK membrane, 85 mW cm −2. Chemical synthesis of the semi-IPN membranes is identified using FTIR, and its ion cluster dimension examined using SAXS. The dimensional stability associated with water swelling and dissolution is investigated at different temperatures, and the semi IPN membranes dimensionally stable in water at elevated temperature.

Synthesis of proton-conductive sol–gel membranes from trimethoxysilylmethylstyrene and phenylvinylphosphonic acid

Novel proton-conductive inorganic–organic hybrid membranes were synthesized from (trimethoxysilylmethyl)styrene (TMSMS) and phenylvinylphosphonic acid (PhVPA) mixed at various ratios using radical copolymerization followed by the sol–gel process. Self-standing, homogeneous, highly transparent membranes were synthesized. TG-DTA analysis indicated that these membranes were thermally stable up to 180 °C. FT-IR and 13C NMR revealed that the functionalized alkoxysilane was copolymerized with phenylvinylphosphonic acid. The phosphonic acid groups of the TMSMS/PhVPA copolymer were chemically bound to the organosiloxane network formed via the hydrolysis and polycondensation reaction between the silanol groups of TMSMS. The proton conductivity of the hybrid membranes increased with the phosphonic acid content. The TMSMS/PhVPA membrane of a 1/4 ratio revealed conductivities of 3.7 × 10 −2 S cm −1 under 100% R.H. at 130 °C and 9.5 × 10 −4 S cm −1 under about 19.2% R.H. at 130 °C.

Functionalized periodic mesoporous organosilica fibers with longitudinal pore architectures under basic conditions

Hierarchically organized functionalized periodic mesoporous organosilica (PMO) fibers with longitudinal pore architectures have been prepared via a simple one-pot synthesis procedure from the co-condensation of 1,2-bis(triethoxysilyl)ethane (BTESE) with either of two kinds of trialkoxysilanes, (3-triethoxysilylpropyl) isocyanate (ICP), or 1-[3-(trimethoxysilyl)propyl] urea (UREDO) under basic conditions. The influence of organosilica source and temperature on the formation and the internal pore architecture of the functionalized PMO fibers were investigated. The pore channels in both types of PMO nanofibers are hexagonally packed, in which pore channels are aligned parallel to fiber axis. The diameters of the fibers range from 50 to 300 nm, and the lengths are up to 7 μm. Electron microscopy and X-ray diffraction investigations were carried out to elucidate the morphological and structural features of the functionalized PMO fibers. The formation of well-condensed and interconnected organosiloxane network was proven by 29Si CP/MAS NMR spectroscopy. How the nature of organic groups has impacted on the surface areas and pore volumes were evaluated by N 2 isotherms.

A Simple Approach to Synthesize and Bond Organosiloxane Films on Injection-Molded Polyolefins

A simple method was devised to fabricate and anchor organosiloxane coatings along low-surface-energy plastics without resorting to chemical pre-treatment of the polymer surface. Polypropylene tubes were purposely distended by exposure to toluene-based solutions. An established solvent of many organic polymers and compounds, toluene not only perfused into the plastic via gradual intercalation of accessible polymer chains, but it also facilitated the entry of less compatible reagents as co-perfusates. The reagents, typically aminoalkyl si lanes, were activated either concomitant to perfitsion of polypro-pylene or during a subsequent hydrolysis step. Freed silanol groups, interacting along and beneath the Surface of the plastic, reacted to form a network held together by siloxane bonds. The type of network formed and presented herein was interpreted as an amorphous aminopropylsiloxane-silanol hydrate film, with overall thickness partially submerged and caught in the matrix of the plastic. This concept to intertwine a growing organosiloxane network and a compliant matrix precluded the conventional methods normally used to improve bonding on hydrophobic plastics. A comparison of ninhydrin color yields suggested that films were more effectively and conveniently synthesized when aminopropyltri-methoxysilane was applied in water-saturated toluene. It follows that by integrating low-temperature hydrothermal processing into this strategy, inorganic-organic hybrids or inorganic oxide films may be formed oil pre-molded plastics and feature traits such as covalent-like fastness and gas impermeability.

One-pot synthesis of phenyl- and amine-functionalized silica fibers through the use of anthracenic and phenazinic organogelators

In a typical one-pot synthesis procedure, hybrid organosilica fibers were grown by templating the co-condensation between TEOS and selected organotrialkoxysilanes (20 mol% of phenyltriethoxysilane, PTES, or aminopropyltriethoxysilane, APTES) through the use of DDOA (2,3-bis(n-decyloxy)anthracene) and DUOP (2,3-bis(n-undecyloxy)phenazine) organogelators in a compatible solvent (ethanol or acetonitrile, respectively). Interestingly, the successful replication of organogelator fibrous assemblies was accomplished working at low pH values (ca. 2–3) in acid catalysed conditions. By SEM and TEM characterizations the hybrid organosilicas were seen to consist of submicronic fibers (100–200 nm) aggregated into highly anisotropic fibrous bundles (1–15 µm thick). In addition, molecular and/or supramolecular interactions between the organogelator and the growing organosiloxane network proved to have an important effect on fiber thickness and on fiber aggregation (intertwined/co-aligned, lamellar- or ribbon-like fibrous bundles). After removal of the organogelator (by calcination or by Soxhlet washing), the fibrous morphologies were perfectly conserved, and the presence of phenyl and amine moieties was confirmed by FTIR spectroscopy and also by elemental chemical analysis. The formation of a well-condensed and interconnected organosiloxane network was proven by 29Si MAS NMR spectroscopy. Moreover, the accessibility and reactivity of the grafted amine groups were also corroborated by performing a simple post-functionalization heterogeneous reaction with diluted benzaldehyde.

Study of poly(organosiloxane) network formation by analysis of viscoelastic characteristics

The process of crosslinked polymer formation was studied for the case of anionic copolymerization of spirocyclosiloxane with α, ω-oligodimethylsiloxane by the methods of small-amplitude periodic deformation, sol-gel analysis and swelling. The effect of initial content of initiator and spirocyclosiloxane on the time dependences of dynamic modulus and gel-fraction was demonstrated. The structural parameters of the networks were determined The mean length of the elastically active chain in the network considerably exceeds the chain length of the initial α, ω-oligodimethylsiloxane. Increased spirocyclosiloxane content affects the viscoelastic characteristics of the network.