Hyperbranched Polyethoxysiloxane Research Articles

Quantitative Elasticity Mapping of Submicron Silica Hollow Particles by PeakForce QNM AFM Mode.

Silica hollow spheres with a diameter of 100-300 nm and a shell thickness of 8±2 nm were synthesized using a self-templating amphiphilic polymeric precursor, i.e., poly(ethylene glycol)-substituted hyperbranched polyethoxysiloxane. Their elastic properties were addressed with a high-frequency AFM indentation method based on the PeakForce QNM (quantitative nanomechanical mapping) mode enabling simultaneous visualization of the surface morphology and high-resolution mapping of the mechanical properties. The factors affecting the accuracy of the mechanical measurements such as a local slope of the particle surface, deformation of the silica hollow particles by a solid substrate, shell thickness variation, and applied force range were analysed. The Young's modulus of the shell material was evaluated as E=26±7 GPa independent of the applied force in the elastic regime of deformations. Beyond the elastic regime, the buckling instability was observed revealing a non-linear force-deformation response with a hysteresis between the loading and unloading force-distance curves and irreversible deformation of the shell at high applied forces. Thus, it was demonstrated that PeakForce QNM mode can be used for quantitative measurements of the elastic properties of submicon-sized silica hollow particles with nano-size shell thickness, as well as for estimation of the buckling behaviour beyond the elastic regime of shell deformations.

Self-Templating Synthesized Silica Nanocapsules and Fabrication of Nanocomposite for Enhancing the Anti-Felting of Wool Fabrics

In this study, silica nanocapsules within silica shell (SNPs) based on an amphiphilic silica precursor polymer – poly (ethylene glycol) substituted hyperbranched polyethoxysiloxane (PEOS-m PEG) was synthesized through a self-assembly method in a fully aqueous with high efficiency. SNPs was homogeneously distributed in waterborne polyurethane to study the influence on the mechanical properties of the nanocomposite as a novel anti-felting agent for wool fabric. The mechanical properties of the nanocomposite anti-felting agent films improved in comparison with the neat polymer. The storage modulus and tensile strength was increased by 143% and 49%, respectively. The novel nanocomposite anti-felting agent was coated on wool fabrics by a pad-dry-cure process. The area shrinkage of the obtained wool fabrics with nanocomposite was 0.8%, much lower than the fabric treated with the same dosage of neat polymer, 4.1%. The warp tensile strength of the wool fabric was increased to 212.2N with lower polymer consumption by 40%.

Sodium 3-azidopropyldialkoxysilanolate - A versatile route towards new functional 1,2,3–triazole based hyperbranched polyorganoalkoxysiloxanes

A new type of hybrid organosilicone polymer combining the coordination ability of triazole rings with the advantages of the highly branched topological structure of the flexible polysiloxane backbone was synthesized, characterized and exploited for the formation and stabilization of silver nanoparticles.In this study a series of functional 3-azidopropylethoxysiloxanes and poly-1,2,3-triazoleorganoethoxysiloxanes with controlled molecular architectures were synthesized and characterized for the first time using controlled condensation of the new AB2-type sodiumoxo-3-azidopropyldiethoxysilane monomer and the Copper(I)-catalyzed azide-alkyne cycloaddition “Click chemistry” process. The new 1,2,3-triazole-based hybrid polymers with a functional hyperbranched polyethoxysiloxane polymer backbone showed the ability to stabilize ultrasmall silver nanoparticles.The synthesized structures were characterized using 29Si NMR, 1H NMR, FTIR, Mass-spectrometry, and GPC. Polymer nanocomposites with the stabilized silver nanoparticles were characterized by transmission electron microscopy (TEM).

A Convenient and Versatile Strategy for the Functionalization of Silica Foams Using High Internal Phase Emulsion Templates as Microreactors.

Functional porous materials show extensive applications in the environment, biology, aerospace, and so on. In this work, the generation of silica foams and functionalization of pore surface were simultaneously realized through an interfacial sol-gel reaction within high internal phase emulsion (HIPE) microreactors, where a hyperbranched polyethoxysiloxane (PEOS) was used as the sole stabilizer for the HIPEs. With various functional substances containing amino, epoxy, and carboxyl groups initially dissolved in the aqueous phase of HIPEs, these functional groups could be grafted onto the pore surface in the process of forming silica foams. Amino-functionalized silica foam showed fast adsorption of sunset yellow, and the adsorption capacity could reach as high as 1213.13 mg/g. Sodium polyacrylate-modified silica foam exhibited good adsorption capacity of cationic dyes and metal ions, e.g., 280.11 mg/g to methylene and 226.24 mg/g to Cu(II). Epoxy-functionalized silica foam particles were confirmed with a pronounced activity at the oil/water interface due to their Janus-like surface, which could be used as Pickering stabilizer. This HIPE-based synthesis strategy for silica foams shows promising future in adsorption, emulsion stabilization, and compatibilization.

Polyethylene–Silica Nanocomposites with the Structure of Semi‐Interpenetrating Networks

AbstractOrganic–inorganic nanocomposites with the structure of interpenetrating or semi‐interpenetrating networks are considered as advanced materials, since they have improved thermal and mechanical properties. An alternative approach to the preparation of such hybrid systems is proposed. It is based on the synthesis of silica from the precursor of hyperbranched polyethoxysiloxane by the hydrolytic condensation reaction in the volume of pores of a polymer matrix (bulk porosity is 40 vol%) stretched via the environmental crazing mechanism. Polyethylene–silica nanocomposites with the structure of semi‐interpenetrating networks when the content of silica is not less than 20–25 wt% are obtained. These composites can undergo an additional phase separation at a temperature of 160 °C (above the melting point of polyethylene), which is accompanied by an increase in the size of the polymer phase with the formation of macrophases. At the same time, the environment (orthophosphoric acid), in which the composite is heated, fills the pores that have appeared. As a result, the content of the third component with the new functionality increases up to 50 wt%, which allowed us to impart proton‐conducting properties to the composite material and preserve its shape stability.

Microgel/silica hybrid colloids: Bioinspired synthesis and controlled release application

In the present work, we demonstrate that polymer based functional microgels can be used as autocatalytic template for the bioinspired deposition of silica nanoparticles inside the microgel network under ambient conditions. Temperature responsive poly(N-vinyl caprolactam) based microgels were synthesized by precipitation polymerization using glycidyl methacrylate as a comonomer. These microgels were further reacted with aminoethanthiol to develop amine functional groups inside the microgels. A water soluble silica precursor (PEGPEOS) was developed by modification of hyperbranched polyethoxysiloxane with polyethylene glycol monomethyl ether. Microgel/silica hybrid colloids were prepared by simultaneous PEGPEOS conversion and silica deposition in the microgels. TEM studies showed that silica nanoparticles of approximately 10 nm in size were deposited inside the microgel network owing to the strong acidbase interaction between the acidic silica and basic amine groups. DLS results indicated that the incorporation of silica nanoparticles reduced the thermal sensitivity of microgels. Molecular dynamics simulations were performed to investigate the interaction between silica precursor and microgels based on radial distribution function and interaction energy. The developed hybrid microgels were further explored for controlled release of aspirin used as a model drug. The preliminary results indicated that the presence of silica rich domains in the microgel network remarkably retarded aspirin release.

Inclusion of Phase-Change Materials in Submicron Silica Capsules Using a Surfactant-Free Emulsion Approach.

Microencapsulation of phase-change materials is of great importance for thermal energy-storage applications. In this work, we report on a facile approach to enclose paraffin in mechanically strong submicron silica capsules without the addition of any classical organic surfactants. A liquid silica precursor polymer, hyperbranched polyethoxysiloxane (PEOS), is used as both silica source and stabilizer of oil-in-water emulsions because of its hydrolysis-induced interfacial activity. Hydrophobic paraffin is microencapsulated in silica with quantitative efficiency simply by emulsifying the mixture of molten paraffin and PEOS in water under ultrasonication or high-shear homogenization. The size of the capsules can be controlled by emulsification energy and rate of subsequent stirring. The silica shell, whose thickness can be easily tuned by varying the paraffin to PEOS ratio, acts as an effective barrier layer retarding significantly the evaporation of enclosed substances; meanwhile, the microencapsulated paraffin maintains the excellent phase-change performance. This technique offers a low-cost, highly scalable, and environmentally friendly process for microencapsulation of paraffin phase-change materials.

Ultralight Silica Foams with a Hierarchical Pore Structure via a Surfactant-Free High Internal Phase Emulsion Process.

An ultralight silica aerogel is among the most versatile materials available for technical applications; however, it remains a huge challenge to reduce its manufacturing cost. Here, we report on a simple approach for the preparation of silica foam monoliths with ultrahigh porosity up to 99.5% and specific surface area as high as 755 m2 g-1, which are similar to those of an aerogel. Our strategy is based on the effective stabilization of water-in-oil high internal phase emulsions by a hydrophobic silica precursor polymer, hyperbranched polyethoxysiloxane because of its hydrolysis-induced amphiphilicity. After conversion of this precursor polymer to silica, the emulsions are solidified without significant volume shrinkage. Thus, mechanically strong macroporous silica monoliths are obtained after removal of its liquid components. According to nitrogen sorption data, the resulting silica foams exhibit a high specific surface area and a foam skeleton consisting of both micropores (<2 nm) and mesopores (2-50 nm). The pore size, porosity, and surface area can be regulated by varying pH as well as the concentration of the silica precursor in the oil phase. In addition, the pore size can be adjusted by controlling shear force during emulsification. This work opens a new avenue for producing ultralight porous materials amenable to numerous applications.

Hybrid nanostructured particles via surfactant-free double miniemulsion polymerization

Double emulsions are complex fluid systems, in which droplets of a dispersed liquid phase contain even smaller dispersed liquid droplets. Particularly, water-in-oil-in-water double emulsions provide significant advantages over simple oil-in-water emulsions for microencapsulation, such as carrier of both aqueous and oily payloads and sustained release profile. However, double emulsions are thermodynamically unstable systems consisting typically of relatively large droplets. Here we show that nanoscale water-in-oil-in-water double emulsions can be prepared by adding a silica precursor polymer, hyperbranched polyethoxysiloxane, to the oil phase without any additional surfactants. The resulting double miniemulsions are transformed to robust water@SiO2@polymer@SiO2 nanocapsules via conversion of the precursor to silica and polymerization of the oil phase. Other intriguing nanostructures like nanorattles and Janus-like nanomushrooms can also be obtained by changing preparation conditions. This simple surfactant-free double miniemulsion polymerization technique opens a promising avenue for mass production of various complex hybrid nanostructures that are amenable to numerous applications.

Multiple Functionalized Hyperbranched Polyethoxysiloxane Promotes Suzuki Coupling Asymmetric Transfer Hydrogenation One‐Pot Enantioselective Organic Transformations

AbstractUtilization of amphiphilic poly(ethylene glycol) monomethyl ether modified hyperbranched polyethoxysiloxane as a support for the construction of bifunctional heterogeneous catalysts enables a highly efficient catalytic system thanks to its amphiphilic nature in aqueous organic transformations. Herein, through a three‐component self‐assembly procedure, we incorporate palladium/phosphine and chiral ruthenium/diamine functionality within poly(ethylene glycol) monomethyl ether modified hyperbranched polyethoxysiloxane, fabricating a multiple functionalized polyethoxysiloxane based mesoporous material. Structural analyses and characterizations disclose that well‐defined dual single‐site active centers are distributed uniformly within monodisperse mesoporous silica nanoparticles. As a bifunctional heterogeneous catalyst, this material performs the one‐pot enantioselective tandem reaction of Pd‐catalyzed Suzuki cross‐coupling and Ru‐catalyzed asymmetric transfer hydrogenation, affording various chiral biaryl alcohols with high yields and up to 99 % enantioselectivity. Furthermore, the catalyst can be recovered and recycled eight times without loss of its catalytic activity, demonstrating the practicability of the preparation of optically pure biaryl alcohols in one‐pot organic transformation.

Development of complete silica thin films based on functional hyperbranched polyalkoxysiloxanes

A precursor polymer has been designed on the basis of an idea of conversion of hyperbranched polymer to an inorganic substance by lithographic procedure. For this purpose hyperbranched polyethoxysiloxane (PEOS) was synthesized via a one-pot catalytic condensation reaction of tetraethoxysilane with acetic anhydride. PEOS was modified with cyclohexanol via a catalytic trans-esterification reaction. The products were characterized by means of 1H and 29Si NMR spectroscopy, elemental analysis and size exclusion chromatography. The thin silica films were formed by spin-coating of chloroform solutions of PEOS and cyclohexanol-modified PEOS (CH-PEOS) on silicon wafer substrates with subsequent H2-plasma treatment. CH-PEOS layer containing a photoacid could be cross-linked upon UV-irradiation. This approach was used to develop patterned thin silica films, which were analyzed by field emission scanning electron microcopy and atomic force microscopy. Well defined sharp silica patterns were obtained and further conversion of the layer to pure silica was carried out by removing organic species using H2 plasma treatment.

Amphiphilic Hyperbranched Polyethoxysiloxane: A Self-Templating Assembled Platform to Fabricate Functionalized Mesostructured Silicas for Aqueous Enantioselective Reactions

Fabrication of amphiphilic mesostructured silica as a heterogeneous catalyst is beneficial to facilitate an aqueous reaction due to its highly dispersed nature in water. In this work, by taking advantage of a self-templating assembled strategy, we construct two types of mesostructured silicas as heterogeneous catalysts, chiral ruthenium/diamine-functionalized and chiral cinchonine-based squaramide-functionalized heterogeneous catalysts, through the use of amphiphilic poly(ethylene glycol) monomethyl ether-modified hyperbranched polyethoxysiloxane as a silica precursor. As presented in the study, the chiral ruthenium/diamine-functionalized catalyst performs an asymmetric transfer hydrogenation of acyclic α-trifluoromethylimines to chiral α-trifluoromethylamines in water, whereas the chiral squaramide-functionalized catalyst enables efficiently asymmetric Michael addition of acetylacetone to nitroalkenes in brine. Both highly catalytic performances are attributed to the combined multifunctionalities of well...

A Facile One-Step Approach toward Polymer@SiO2 Core–Shell Nanoparticles via a Surfactant-Free Miniemulsion Polymerization Technique

We present a surfactant-free miniemulsion process for the preparation of monodisperse polystyrene@SiO2 nanoparticles with a well-defined core–shell structure. The strategy utilizes a silica precursor polymer, hyperbranched polyethoxysiloxane (PEOS), as a sole miniemulsion stabilizer due to its water insolubility and at the same time pronounced amphiphilicity induced by hydrolysis at the oil/water interface. The core–shell particles are obtained by emulsifying a PEOS/styrene mixture in water and subsequent heating to initiate polymerization. As the polymerization proceeds, driven by osmotic pressure and incompatibility with polystyrene, PEOS macromolecules migrate continuously toward the oil/water interface where sol–gel reaction takes place. As soon as the polymerization is completed, PEOS is fully expelled from the polymer phase and is converted to silica on the polystyrene surface. This method allows an easy control of silica shell thickness by varying the PEOS concentration. The particle size, on the o...

Synthesis and Characterization of Organo-Inorganic Nanoobjects Based on Hyperbranched Polyethoxysiloxanes

The synthetic scheme for obtaining modified molecular silicasols based on hyperbranched polyethoxysiloxane (HPEOS) is presented in this work. The synthetic scheme includes several stages; the first and most important one represents polycyclization and simultaneous modification of HPEOS with either organosilanols or disiloxanes. The following stages are polymer-analogous reactions affecting only the external layer. The obtained nanoparticles are nanogels with specific morphology of inorganic silica core soluble in anhydrous organic solvents. All the hybrid systems were characterized by means of elemental analysis, GPC, IR and NMR spectroscopy. Some physical and chemical parameters were determined for all samples after fractionation. Synthesized molecular silicasols are ready-made universal models for investigations of interactions between macromolecules of polymer matrix and nanoparticles, and evaluation of various factors, such as the chemical nature of the external layer or particle core size, which have a great influence upon properties of nanocomposites.

Microencapsulation of Hydrophobic Liquids in Closed All-Silica Colloidosomes

A facile approach for the microencapsulation of hydrophobic liquids in closed solid all-silica colloidosomes is reported. The method is based on the formation of oil-in-water emulsions stabilized by silica nanoparticles and subsequent gluing of the particles at the water/oil interface by a silica precursor polymer-hyperbranched polyethoxysiloxane. By this means different oils are successfully enclosed in hence formed all-silica colloidosomes with almost 100% efficiency. Via a systematical study it is demonstrated that this process is a delicate interplay between the emulsion stability, oil polarity, and sol-gel reaction kinetics. This approach allows fabricating microcapsules of hydrophobic liquid substances in a mechanically stable, chemically inert, and biocompatible matrix, silica, with high encapsulation capacity and a controlled release profile.

Encapsulation of Laccase in Silica Colloidosomes for Catalysis in Organic Media

We report on the encapsulation of a laccase solution in silica colloidosomes of different shell structures and the study of catalytic performance of the encapsulated enzyme in toluene. The encapsulation is carried out by linking silica nanoparticles at the water/oil interface using hyperbranched polyethoxysiloxane (PEOS) in an aqueous-laccase-solution-in-toluene Pickering emulsion. By varying the weight ratio of silica particles to water (Rs/w), colloidosome shell can be adjusted from a particle monolayer up to a bilayer bound with a sandwiched nanoporous silica thin film formed from PEOS. The encapsulated laccase exhibits catalytic activity and reusability that are controlled by Rs/w. With the increase of Rs/w the reusability of the enzyme improves, meanwhile, its activity declines. This method allows fabricating enzyme microcapsules with tailored activity and controlled release properties.

Self‐Templating Amphiphilic Polymer Precursors for Fabricating Mesostructured Silica Particles: A Water‐Based Facile and Universal Method

A facile and universal approach is reported for the preparation of silica particles of various mesostructures based on the self-assembly of amphiphilic precursor polymers in water and subsequent condensation. Depending on the hydrophilization degree of hyperbranched polyethoxysiloxane, various silica morphologies including mesoporous particles, hollow nanospheres and ultrasmall particles with high application potential are fabricated.

Perfluorosulfonic acid ionomer – silica composite membranes prepared using hyperbranched polyethoxysiloxane for polymer electrolyte membrane fuel cells

We report on the preparation and characterization of perfluorosulfonic acid ionomer (PFSA) – silica composite membranes using hyperbranched polyethoxysiloxane (PEOS) as silica precursor. The membranes were formed via an in situ sol–gel process of PEOS in a PFSA solution and subsequent solution casting. Transmission electron microscopy and small-angle X-ray scattering data showed that at low silica content ultra-small silica particles with a size smaller than the diameter of the ionic channels were homogeneously dispersed in the PFSA matrix. Such morphology leads to enhanced proton mobility as probed by impedance spectroscopy and 1H solid-state NMR, and eventually resulted in the improvement of fuel cell performance.

Use of hyperbranched polyethoxysiloxane to improve the resistance of thermoplastic polyimide coatings to atomic oxygen environment

Polyimide thin films both unmodified and modified with hyperbranched polyethoxysiloxane were treated with accelerated oxygen plasma flow to imitate a low Earth orbit environment. The resulting changes in the surface morphology were studied using scanning electron microscopy. The erosion yield values were calculated and the relative stability of the tested samples was established. It was shown that the polyimide-polyethoxysiloxane composites have higher atomic oxygen resistance owing to, presumably, the siloxane particles dispersed uniformly in the polyimide matrix. The study found that all plasma-treated samples exhibit the same fibrous, carpet-like surface morphology with some minor variations caused by differences in the chemical composition of polymers.

Synthesis and Characterization of Hybrid Core–Shell Systems Based on Molecular Silicasols

New hybrid “rigid inorganic core–soft organic shell” systems based on molecular silicasols were synthesized by applying different synthetic schemes. Inorganic core was composed of molecular silicasols, which were synthesized from hyperbranched polyethoxysiloxane and tetraethoxysilane by polymer chemistry methods. Different organic modifiers were used to form soft shell of the hybrid particles. Obtained compounds were characterized by elemental analysis, GPC, IR and NMR spectroscopy. These systems will be designated for use as model objects for investigation of nanoparticles–polymer matrix interactions in polymer nanocomposites.