Polysiloxane Particles Research Articles

Adsorption and photocatalytic degradation performances of methyl orange-imprinted polysiloxane particles using TiO2 as matrix

Adsorption and photocatalytic degradation performances of methyl orange-imprinted polysiloxane particles using TiO2 as matrix

Preparation of superhydrophobic surface from raspberry like particles of bifunctional polyssesquioxane

AbstractIn this article, we selected MTMS and ETMS as mixed precursors to generate polysiloxane particles on the surface of styrene copolymer microspheres, forming raspberry‐like particles. The best experimental formula was obtained by orthogonal test. When the ratio of MTMS and ETMS was 3:1, the hydrophobic properties of composite particles reached the best, with a water contact angle (WCA) of 163° and a WSA of 3°. The hydrophobic models of raspberry particles were established. And the influence of gas–liquid contact components, surface roughness and precursor ratio on hydrophobic properties was clarified by theoretical calculation, Fourier transform infrared and X‐ray diffraction analysis. The prepared superhydrophobic surface shows great application potential in self‐cleaning, antifouling and other fields.

Fabrication of dual-sensitive heterogeneity organohydrogel with temperature/surrounding-phase regulatory superomniphobic surface for on-demand oil/water separation

Oil/water separation is difficult but essential not only for the sustainable development of human society but also for the protection of the ecological. Developing materials with controllable wettability for efficient on-demand oil/water separation is urgently needed. Inspired by the structural and functional features of the cellular plasma membrane, in this work, a dual-sensitive heterogeneity organohydrogel was fabricated by combining thermal-responsive poly(N-isopropylacrylamide) (PNIPAM) and reactive polysiloxane particles (RPP). The resulting organohydrogel can adapt to temperature stimuli to realize super-wettability conversion (from superhydrophilicity (WCA is 0°) to superhydrophobicity (WCA is ∼160.5°) under-oil). In the dry state, the wettability of organohydrogel can also be adjusted to superamphiphobicity under water (OCA is ∼151.5°) or under oil (WCA is ∼162.4°) after being pre-wetted with water or oil. In addition, the outstanding film-forming property of the organohydrogel led to the formation of a coating layer on fiberglass fabric. Exhilaratingly, the coated fiberglass fabric displays stable recyclability, excellent chemical tolerance, and temporal stability, as well as demonstrates an excellent super-wettability conversion even after 90 cycles of the peeling test. Under different pH solutions, the WCA on the coated material surface was always 0° at 20 °C, while the measured WCA was always above 150° at 45 °C. Moreover, the coated fiberglass cloth could achieve on-demand oil/water mixture separation and selective separation efficiency above 98.5%. Thus, our work may pave the new ideas in the application of on-demand oil/water separation and oily wastewater purification in the further.

Thermal and physico-mechanical properties of antifriction solid lubricant for cold plastic deformation of titanium alloys

The results of the investigations of thermophysical characteristics, thermomechanical and mechanical properties of epoxy-polysiloxane nanocomposites with different contents of modifying additives in the presence of fine-grained antifriction fillers. It is shown that the joint influence of the modifier (polysiloxane particles) and filler (graphite) on the formation of the composite structure during the hardening results in the essential improvement of its physico-mechanical properties. The optimal formulation of a composition to be used as an antifriction solid lubricant for a cold plastic deformation of titanium alloys is determined.

Controlled Silylation of Nanofibrillated Cellulose in Water: Reinforcement of a Model Polydimethylsiloxane Network.

A comparative approach for the surface silylation of nanofibrillated cellulose (NFC) in water is proposed through an environmentally friendly sol-gel route based on alkoxysilanes. NFC suspensions were freeze-dried under controlled conditions in the presence of methyltrimethoxysilane used as a model alkoxysilane. Two different protocols that involve different pH values (0.4 and 4) and post-treatment procedures were investigated and compared. Protocol 1 led to a network of nanofibrils in which polysiloxane particles were dispersed, and protocol 2 produced a scaffold of cellulosic fibrils coated by a polysiloxane layer bonded firmly to the cellulosic substrate. Different from protocol 1, protocol 2 imparted the cellulosic material with hydrophobic properties and improved its thermal stability. Moreover, if 1 wt % of fibrils treated by protocol 2 were incorporated into a model polydimethylsiloxane network, substantial improvements of the static and dynamic mechanical properties of the composite were noted.

Solid ceramic SiCO microspheres and porous rigid siloxane microspheres from swellable polysiloxane particles

Solid silicon oxycarbide (SiCO) ceramic microspheres and rigid porous siloxane microspheres were obtained in a two step process. First, polysiloxane microspheres with a large number of Si–OH groups in their bulk and on their surface were synthesized from polyhydromethylsiloxane (PHMS) using a recently developed process. The process included a combination of three reactions of Si–H groups of PHMS occurring in aqueous emulsion and catalyzed by the same Karstedt Pt(0) complex: (i) hydrosilylation of 1,3-divinyltetramethyldisiloxane (DVTMDS), (ii) hydrolysis, (iii) dehydrogenocondensation involving the SiOH groups formed during the hydrolysis. DVTMDS was grafted on PHMS prior to emulsification. Microspheres had a loose structure and were able to absorb a significant amount of organic solvents. In the second step the microspheres were subjected to pyrolysis with heating in the argon atmosphere at following temperatures: 400, 700 and 1000 °C. These heated at 400 °C had micro and mezopores, while those heated at 700 and 1000 °C gave spherical solid SiCO ceramic particles. Polysiloxane microspheres and microspheres obtained by pyrolysis of the former were analyzed by 29Si and 13C MAS NMR, FTIR, SEM, and N2 gas adsorption.

Evaluation of high temperature resistance of white Si–O–C(–H) ceramics in an inert atmosphere

Two kinds of white Si–O–C(–H) ceramic powders, named S900 and S1100, were prepared from cross-linked polysiloxane particles with an average diameter of 6μm. S900 was the product obtained in a hydrogen gas flow at 900°C with a holding time of 1h, whereas S1100 was the product obtained at 1100°C with a holding time of 3h. Heat stability of these ceramic powders in graphite boats were examined within the temperature range of 1200–1600°C in an Ar gas flow. The powder substantially began to degrade beyond 1400°C, which was accompanied by mass loss, fusing of particles and partial cristobalite precipitation. The color of S900, however, became black after the heat treatment at 1400°C before the substantial mass loss, whereas the color of S1100 showed small change to light gray after the heat treatment at 1400°C. The apparent color change of the samples during the heat treatment possibly corresponded to defect incorporation in the Si–O–C(–H) network, whereas the change in chemical composition was minor. At high temperature region, SiO and CO were evolved as a result of SiC–SiO2 reaction, although SiC and SiO2 were defined as virtual phases in the Si–O–C(–H) amorphous.

Influence of high-temperature oxidation on photoluminescent properties of white Si[sbnd]O[sbnd]C(–H) ceramics

SiOC(–H) ceramics were prepared by pyrolyzing densely cross-linked polysiloxane particles in hydrogen at temperatures of 800, 900 and 1100°C. Thermogravimetric–differential thermal analysis (TG–DTA) curves of these SiOC(–H) ceramics in an air flow revealed that the oxidation resistance strongly depended on the decarbonization temperature. On the other hand, these decarbonized samples were oxidized in dry air flow at temperatures of 300, 500, 700, 1000 and 1200°C. After the oxidation in air, photoluminescent (PL) spectra and Fourier transform infrared (FTIR) spectra of the oxidized samples were investigated. In partly organic SiOC(–H) ceramics with high H/C ratios, the intensity of blue PL simultaneously decreased with rapid oxidation. Residual weak PL peaks are probably assigned to defects in silica formed on particle surfaces. In dense SiOC(–H) ceramics with a relatively low H/C ratio, the intensity of white PL gradually decreased with moderate oxidation and the PL peak position shifted to longer wavelengths. Intensity of phosphorescence of the dense SiOC(–H) ceramics was also weakened after oxidation. The decrease of phosphorescence intensity, however, began at a rather low temperature range as compared with that of the apparent PL.

Investigation of photoluminescence of Si−O−C(−H) ceramics at an early stage of decarbonization by using high energy excitation

Si−O−C(−H) ceramics with reduced carbon contents were prepared by pyrolyzing polysiloxane particles in hydrogen at temperatures of 750, 800 and 850 °C. Under HeCd laser irradiation (325 nm), the obtained ceramics show broad spectra peaking at 400–415 nm. On the other hand, the excitation on the higher energy region by an ArF excimer laser (193 nm) induces new PL bands located at short wavelength region of 300 and 355 nm. Such high energy PL bands appear prominently in the ceramics synthesized at 750 °C, and are minor in ceramics synthesized at 800 and 850 °C.

Modification of epoxy resin with polyether-grafted-polysiloxane and epoxy-miscible polysiloxane particles

Polyether-grafted-polysiloxane (FPMS) and epoxy-miscible polysiloxane particles (EMPP) were prepared to improve the toughness of epoxy resin. The chemical structures of the products were characterized by FTIR, 1H NMR, 29Si NMR, and gel permeation chromatography (GPC). The morphology of the EMPP was analyzed by transmission electron microscopy (TEM). The thermal and mechanical properties and morphologies of the polysiloxanes modified epoxy networks were examined by differential scanning calorimetry (DSC), tensile and impact testing, and scanning electron microscopy (SEM). Microspheres were observed in the EMPP modified epoxy network, whereas irregular particles were obtained for the FPMS modified epoxy resin. The FPMS and EMPP effectively improved the tensile and impact strength of the cured epoxies, while the glass transition temperatures (Tgs) were depressed slightly. Moreover, with the same content of modifiers, the EMPP-modified epoxy network exhibited higher impact strength and lower Tgs than the FPMS-modified epoxy network.

Preparation of polysiloxane/perfluorosulfonic acid nanocomposite membranes in supercritical carbon dioxide system for direct methanol fuel cell

In this work, polysiloxane-modified perfluorosulfonic acid (PFSA) membranes were prepared by a directed sol–gel synthesis method with (3-mercaptopropyl) methyldimethoxysilane (MPMDMS) as the precursor of silicon alkoxide in the supercritical carbon dioxide (Sc-CO2) system. Contents of polysiloxane in the modified PFSA membranes were varied according to the added amount of precursor MPMDMS. The chemical and physical properties of these modified PFSA membranes were characterized by using attenuated total reflection-infrared spectra, X-ray diffraction, thermogravimetric analysis, universal testing machine, scanning electron microscopy and transmission electron microscope. The measurement results indicated that the polysiloxane particles were not restricted in the ion clusters and well dispersed in the PFSA membrane with ordered size of about 80–100 nm. In the meanwhile, the polysiloxanes have been incorporated into the hydrophobic fluorocarbon backbone regions and interacted with C–F backbones of PFSA polymers. Dimensional stability of the modified PFSA membrane was improved after the impregnation by using Sc-CO2. The modified membranes almost can remain the same high tensile strength as the pristine membrane. Performance of these modified membranes was evaluated in terms of proton conductivity and methanol permeability. The highest selectivity value (ratio of proton conductivity to methanol permeability) of the modified membrane was about 75.6% higher than that of pristine PFSA membrane because of its higher proton conductivity and lower methanol permeability. All the results indicated that this novel synthesis method in Sc-CO2 system is a promising method to improve the properties of PFSA membrane for direct methanol fuel cell application.

Two examples of nanostructured gold surfaces as biosensors. Surface-enhanced chemiluminescence and double detection by surface plasmon resonance and luminescence

In this paper, we present a review of our activities in the field of gold biosensors. Nanostructured gold surfaces can be used in biology for their plasmonic and/or catalytic properties. In a first part, we show how the gold plasmonic properties allow the detection of the biotin-streptavidin binding by two types of techniques: extinction spectroscopy and also luminescence spectroscopy when the probe (here the streptavidin) is labelled by polysiloxane particles encapsulating fluorophores. In a second part, we demonstrate that the catalytical properties of gold corrugated surfaces can significantly enhance the chemiluminescence of luminol brought at vicinity. We found that the surface-enhancement induced by gold is two times of magnitude greater than that induced by silver.

How nanoparticles encapsulating fluorophores allow a double detection of biomolecules bylocalized surface plasmon resonance and luminescence

The paper shows how polysiloxane particles encapsulating fluorophores can besuccessfully used to detect biotin–streptavidin binding by two types of technique. Afterfunctionalization of the particles by streptavidin, the fixation of the biomolecule can indeedbe detected by a shift of the localized surface plasmon resonance of the biotinylated golddots used as substrate and by the luminescence of the fluorophores evidenced byscanning near-field optical microscopy. The development of particles allowingsuch a double detection opens a route for increasing the reliability of biologicaldetection and for multi-labelling strategies crossing both detection principles.

Polymerization in Surfactant Liquid Crystalline Phases

We report the formation of cross-linked polysiloxane particles having rodlike and sheetlike morphologies by condensation of monomers in organized liquid crystalline mesophases of nonionic surfactants. The characteristic diffraction pattern obtained from the liquid crystalline surfactant assembly is preserved during polymer synthesis. The polymer colloids are rodlike when synthesized in a hexagonal mesophase and are sheetlike when synthesized in a lamellar mesophase. Interestingly, the size of the polymer particles is on the order of micrometers, viz. 3 orders of magnitude larger than the characteristic size of the surfactant mesophase. Thus, the polymers phase separate from the liquid crystalline phase during polymerization, and organize to resemble the mesophase geometry. The polymer particles are organized so as to minimize the elastic distortion of the surfactant mesophase after they phase separate. We speculate that the observed particle morphologies are formed due to the slow kinetics of polycondensa...

Growth Kinetics and Morphology of Self-Assembled Monolayers Formed by Contact Printing 7-Octenyltrichlorosilane and Octadecyltrichlorosilane on Si(100) Wafers

The growth kinetics and morphologies of self-assembled monolayers deposited by contact printing 7-octenyltrichlorosilane (OCT) and octadecyltrichlorosilane (OTS) on Si(100) were studied by ellipsometry and atomic force microscopy. We found that, for both OCT and OTS, full monolayers could be obtained at room temperature after printing times of 120-180 s; the printing-based monolayer assembly processes follow apparent Langmuir adsorption kinetics, with the measured film growth rates increasing both with the ambient humidity and with concentration of the ink used to load the stamp. At a dew point of 10 degrees C and an ink concentration (in toluene) of 50 mM, the observed film growth rate constant is 0.05 s(-)(1). When the printing was carried out at a lower ambient humidity (dew points of 1-3 degrees C), the measured rates of assembly were approximately a factor of 2 slower. Increasing the deposition temperature from 25 to 45 degrees C under these conditions increased the film growth rate only slightly. The morphology of the films depends on the identity of the ink. Uniform, high-coverage films could be obtained readily from the eight-carbon chain length adsorbate OCT, provided that the stamp was not overloaded with the ink; for high concentrations outside of the optimal range, the surface presented significant numbers of adsorbed particles ascribed, in part, to siloxane polymers formed by hydrolysis of the ink on the stamp before printing. In marked contrast, for the 18-carbon adsorbate OTS, the printed films always consisted of a mixture of a uniform monolayer plus adsorbed polysiloxane particles. The different film morphologies seen for OCT and OTS are proposed to result from the different transfer efficiencies of the organotrichlorosilane relative to polysiloxane hydrolysis products formed during the printing process. These transfer efficiencies exhibit sensitivities related to the permeation of the poly(dimethylsiloxane) (PDMS) stamp by the silane reagents. Short-chain inks such as OCT evidently permeate the PDMS stamp more deeply than longer-chain inks such as OTS. This difference, and the different diffusion rates of ink vs oligomeric silane hydrolysis products, determines the film morphology obtained by contact printing. The mass transfer dynamics of the process thus yield surface layers derived from varying quantities of siloxane oligomers, which subsequently transfer to the substrate along with unhydrolyzed silane adsorbate during the printing step. The structural evolution of the contact-printed films so obtained is strikingly different from that of SAMs prepared by immersion.

Modification of epoxy resin with siloxane containing phenol aralkyl epoxy resin for electronic encapsulation application

A process was developed to incorporate stable dispersed polysiloxane particles into a phenol aralkyl novolac epoxy resin, which was used as an ingredient in the encapsulant formulation to withstand the thermal stress. The mechanical and dynamic viscoelastic properties and morphologies of rubber-modified epoxy networks were studied. A “sea-island” structure (“islands” of silicone rubber dispersed in the “sea” of an epoxy resin) was observed in cured rubber-modified epoxy networks via SEM. The dispersed silicone rubber-modified aralkyl novolac epoxy resin effectively reduces the stress of cured epoxy molding compounds by reducing flexural modulus and the coefficient of thermal expansion (CTE), while the glass-transition temperature ( T g) was hardly depressed. Electronic devices encapsulated with the dispersed silicone rubber-modified epoxy molding compounds have exhibited excellent resistance to the thermal shock cycling test and have resulted in an extended use life for the devices.

Self-assembled monolayers prepared from ω-thiophene-functionalized n-alkyltrichlorosilane on silicon substrates

Self-assembled monolayers (SAMs) of thienyl-functionalized n-alkyltrichlorosilane (11-(3-thienyl)undecyltrichlorosilane [TUTS]) have been prepared by adsorption from solution and characterized by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle measurements, ellipsometry, and scanning electron microscopy (SEM). Using contact angle and SEM measurements, the film preparation protocol was optimized, resulting in reproducible SAM formation with no adverse deposition of polysiloxane particles. XPS and ellipsometry studies confirmed the existence of SAM formation. AFM results show a smooth and homogeneous SAM, with surface roughness of Ra≤0.2 nm, which is slightly higher than the corresponding values for octadecyltrichlorosilane (OTS) SAMs. Such thiophene-based SAM surfaces can be used for surface-initiated polymerization of thiophene. The resulting formed polythiophene layers at non-compatible surfaces offer some practical applications in manufacturing [W. Plieth, A. Fikus, D. Appelhans, H.-J. Adler, German Patent Application No. 2661977 (1998); D. Appelhans, D. Ferse, H.-J. Adler, A. Fikus, W. Plieth, B. Aldolphi et al., J. Electrochem. Soc. (accepted)].

Physical aging of polydimethylsiloxane-modified epoxy resin

The thermal expansion coefficient and physical aging behavior of cured epoxy resins modified with amino-terminated polydimethylsiloxane were investigated. The epoxy resin was tetramethyl biphenol diglycidyl ether. Two factors influenced the thermal expansion behavior and the free volume relaxation of the polysiloxane-modified epoxy systems. One was the miscibility between the epoxy resin and the polysiloxane and the flexibility of the chains in the network system. The intrinsic thermal expansion of the network chains and the volume relaxation increased as a result of building polysiloxane molecules into the network structure. The other factor was the size and concentration of the dispersed polysiloxane particles. The increased local free volume at the interface between the epoxy matrix and the polysiloxane particle resulted in a higher thermal expansion coefficient and led to a large driving force for the volume relaxation during annealing. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1291–1300, 1998

Morphology and properties of polydimethylsiloxane-modified epoxy resin

The morphology and fracture toughness of epoxy resins modified with amino-terminated polydimethylsiloxane (ATPDMS), differing in their molecular weight, and the degree of the preliminary reaction in the melt state were investigated. Tetramethyl biphenol diglycidyl ether (TMBPDGE) was used as the base epoxy resin. The degree of preliminary reaction between epoxy and polysiloxane increased with the decrease of the molecular weight of polysiloxane in the melt state. When the low molecular weight polysiloxane (AT900) was mixed with high molecular weight polysiloxane in the preliminary reaction, the low molecular weight polysiloxane enhanced the compatibility between the epoxy resin and the high molecular weight polysiloxane and produced smaller size and narrow distribution of polysiloxane particles. The small and highly concentrated polysiloxane particles, as determined by scanning electron microscopy improved the fracture toughness of the epoxy resin. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 941–955, 1997

Study of the Preparation of Silicone Rubber Particles with Core-Shell Structure by Seeded Emulsion Polymerization

Silicone rubber particles with core–shell structure were prepared by polymerization of vinyl monomers in the presence of linear or cross-linked poly(dimethyl siloxane–methyl vinyl siloxane) latexes. The monomers were added in either continuous or swelled-continuous modes. Core–shell particles with poly(butyl methacrylate), or poly(methyl methacrylate), as the shell were obtained by using either addition mode. The core–shell structure was not observed for polysiloxane–polystyrene particles. The influence of monomer addition mode, the compatibilities of the monomers and their homopolymers with silicone rubber, and the reactivity ratios of the vinyl monomers with the vinyl group of linear polysiloxane particles, on the formation of the core-shell structure is discussed.