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The restructuring reactions of three siloxane copolymers: poly(Me2SiO-co-HMeSiO), poly(PhMeSiO-co-HMeSiO) and poly(3,3,3-F3PrMeSiO-co-HMeSiO) in the presence of B(C6F5)3 (TPFPB) were investigated. The studied restructuring reactions are the result of the hydride transfer process between two silicon atoms, which is mediated by TPFPB. B(C6F5)3. Initially, the restructuring process produces high molecular weight, branched siloxane copolymers. These copolymers are soluble and capable of forming thin layers. Continuing this reaction leads to cross-linking of the siloxane polymer and the formation of an insoluble gel. The same restructuring process allows the resulting films to be converted into hard coatings after solvent evaporation. The restructuring process of siloxane copolymers was compared with the previously studied restructuring of polyhydromethylsiloxane homopolymer. Although the mechanism of branching and cross-linking is similar, diorganosiloxane units play an important role in the restructuring process as well as influence the properties of the obtained coatings. [ABSTRACT FROM AUTHOR]

A simple method of synthesis for the macroporous SiOC spheroidal microparticles was developed. Preceramic polysiloxane macroporous microbeads were obtained by a one-step aqueous emulsion process involving poly(hydromethylsiloxane) (PHMS) with the addition of FeCl3·6H2O. Thermal treatment of these particles gave various SiOC materials depending on the pyrolysis temperature. Hierarchically porous spheroidal mezo-macroporous ceramers were obtained at 600 °C. Heating at 850–1000 °C gave SiOC ceramic spheroidal particles with about 60% open porosity. Ceramization at 1200–1400 °C led to the particles decorated with ceramic whiskers and wires. Heating at 1600 °C gave wires and spilled ceramic particles. These 1D ceramic structures were formed by a Vapor–Liquid–Solid (VLS) mechanism. [ABSTRACT FROM AUTHOR]

In this overview article, the research on polysiloxane microspheres performed in the authors' laboratory is briefly reviewed. These microspheres are prepared in water emulsion from polyhydromethylsiloxane (PHMS). This polymer is cross-linked in the emulsion process by hydrosilylation using various low molecular weight cross-linkers having at least two vinyl functions. The microspheres contain a large number of silanol groups which give them hydrophilicity and a broad possibility of functionalization by condensation with reactive silanes bearing a functional group in the organic radical. Further transformation of these functions leads to materials for practical use, such as catalysts and biocidal powders. The hydrophilic-hydrophobic properties of the microspheres may be fine-tuned by silylation or modification of the precursor PHMS polymer. Pristine microspheres are highly hydrophilic and well-dispersed in water. They do not adsorb proteins and hydrophobic organic substances. Macropores may be generated in these particles by a simple modification of the emulsion procedure. These microspheres are also very good precursors for ceramic silicon oxycarbide microsphers because they retain their shape in pyrolytic processes even at high temperatures; and they give a high yield of ceramic material. The polysiloxane microspheres heated at 600 °C give micro and mezo porous materials with specific surface above 500 m2/g. When pyrolysed at temperatures 1000–1400 °C, they form solid ceramic microspheres of high strength. They retain spherical shape at 1500 °C although cracks are formed at their surfaces. Etching them with HF(aq) solution gives porous microspheres with specific surface above 1000 m2/g that is almost devoid of SiO2. [ABSTRACT FROM AUTHOR]

Abstract: Electrical conductivity was imparted to a cotton fabric through thermal reduction of graphene oxide. The reduction was enhanced by commercial antioxidants used in the plastics industry. The cotton fabric was coated with GO by the padding method and dipped in antioxidant solution. After drying, the antioxidant assisted reduction of GO was conducted at 220 °C in air. The electrical properties and hydrophobicity of thus-modified fabric were examined. The structure of materials was analyzed by atomic force microscopy and scanning electron microscopy. Application of the antioxidants permitted to reach lower values of surface electrical resistivity of the fabric. After the reduction all fabric samples became hydrophobic.Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract: Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), an antioxidant widely applied in the plastic industry, was used to assist thermal reduction of graphene oxide (GO) on a cotton fabric in air. L-ascorbic acid was also applied for comparison. GO was deposited on the fabric by the padding method. Reduction of GO deposited on fiber surfaces at 180 and 220 °C in air imparted electrical conductivity. For all the materials the conductivity worsened after the reduction during cooling and during the first hours of storage at room conditions. However, the most stable effect of GO reduction was achieved using pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), which assisted the reduction of GO at both 180 and 220 °C, and allowed to obtain the cotton fabric with a stable surface resistivity of 6.6 and 3.7 MΩ/sq, respectively. Moreover, superhydrophobicity of the conductive fabric was achieved by modification with methyltrichlorosilane in an anhydrous environment.Graphical abstract: [ABSTRACT FROM AUTHOR]

Polysiloxane macroporous microspheres and macroporous spheroidal particles were generated from a linear siloxane polymer using a simple emulsion procedure. Osmotic pressure produced by nano-dispersed ionic salt solution in polysiloxane droplets formed in aqueous emulsion is proposed as a mechanism of macropore formation. The competition between cross-linking of the polymer and osmotic swelling of the microspheres governs the shape and porosity of the particles which were characterized by SEM, Si MAS NMR, mercury intrusion porosimetry, and X-ray computed tomography. [ABSTRACT FROM AUTHOR]

The paper presents results of tests on the possibility of utilising fabric with a deposited spatial network of multiwall carbon nanotubes (MWCNTs) as electrodes in processes of their functionalization by electrochemical methods enabling deposition of metal nanoparticles, as well as-by electropolymerization-of conductive polymer nanocoatings. Cyclic voltammetry was employed in the testing, which was used to functionalise various types of fabrics covered with a MWCNT spatial network by depositing silver nanoparticles and polypyrrole (PPy) nanocoating, conferring bioactive properties and significantly increased specific capacity, respectively, to the layered hybrid textile materials acquired this way. [ABSTRACT FROM AUTHOR]

This article presents the findings concerning the preparation and properties of cotton woven fabrics with a conductive network made of multiwall carbon nanotubes deposited on the fiber surface by the padding method. The next stage of treatment consisted of imparting superhydrophobic properties to the fabrics in solution with methyltrichlorosilane (MTCS) in a waterless medium. The tests performed show that the state of surface and water content in cotton fibers exerts a significant influence on the hydrophobic properties of the analyzed samples. In order to explain the differences in hydrophobic properties, the morphology of the cotton fabric surface was examined using samples with various water contents. The formation mechanism of MTCS coatings on cotton fabric has been proposed. [ABSTRACT FROM AUTHOR]

Controlled hydrolysis of 3-chloropropyltrimethoxysilane in water or in methanol–water (1:1 or 1:2 V/V) mixture in a slightly acidic system followed by solvent evaporation under reduced pressure leads to crystalline 3-chloropropylsilanetriol containing 5–10%, of the self-condensation dimer, 1,3-di(3-chloropropyl)1,1,3,3-tetrahydroxydisiloxane. Polycondensation of 3-chloropropylsilanetriol may be used for synthesis of polyhedral oligosilsesquioxanes bearing the chloropropyl group. [ABSTRACT FROM AUTHOR]

Three types of silica particles modified with vinyl groups were obtained: (i) xerogel formed by hydrolytic polycondensation of the mixture of tetramethoxysilane (TMOS) and 1,1,1,7−tetramethoxy-3,5,7-trimethyl-3,5,7-trivinyltetrasiloxane, (ii) mesoporous silica obtained from the same precursors in the presence of the cetyltrimethylammonium bromide (CTAB), and (iii) commercial Fluka silica gel 60A with a vinyltriethoxysilane-treated surface. Vinyl groups on these silica materials were transformed into silyl chloride by hydrosilylation with HMeSiCl. These groups were used to graft living polysiloxane that was synthesized by anionic ring-opening polymerization of 2,4,6-tri(3-chloropropyl)-2,4,6-trimethylcyclotrisiloxane and initiated by BuLi. Chloropropyl groups on the grafted polymer were used to quaternize N,N-dimethyl- n-octylamine. Silica particles with grafted polysiloxane having quaternary ammonium salt (QAS) groups pendant to polymer chains were obtained. Silica material with QAS groups directly attached to the surface were generated by the action of N,N-dimethyl- n-octylamine on particles obtained by the sol-gel process involving tetraethoxysilane (TEOS) with 3-chloropropyltriethoxysilane. The bacteriocidal properties of all these materials were tested in water suspension against five representative strains for Gram-positive and Gram-negative bacteria. Some of the silica-polysiloxane hybrid materials have good antibacterial properties against Gram-positive strains, but not as good as the non-tethered QAS-substituted polysiloxane in water solution. The QAS groups that are directly bonded to the silica material surface are inactive. [ABSTRACT FROM AUTHOR]

Octa(3-chloropropylsilsesquioxane), (T-ClPr)8, and a soluble, low molecular weight, poly(3-chloropropylsilsesquioxane) were subjected to a reaction with dimethyl- n-octylamine to convert part or almost all the chloropropyl groups to corresponding quaternary ammonium salt (QAS) groups. Polysilsesquioxanes containing secondary n-amylammonium salt (SAS) groups were synthesized by reaction of n-alkyl bromides with poly(3-aminopropylsilsesquioxane) of limited molecular weight or by amination of n-amyl bromide with 3-aminopropyltriethoxysilane followed by hydrolysis and polycondensation. The antibacterial activity of these QAS- and SAS-containing silsesquioxane materials against two representative Gram-positive and three representative Gram-negative bacterium strains were tested. Most of these materials showed high or moderate activity against Gram-positive bacteria and moderate or weak activity against Gram-negative bacteria. [ABSTRACT FROM AUTHOR]