Search

Polymer‐metal complexes (PMCs) based on poly(2,2′‐bipyridine‐4,4′‐dicarboxamide‐co‐polydimethylsiloxanes) with cyclometalated di(2‐phenylpyridinato‐C2,N')iridium(III) fragments and cross‐linked by Zn2+ (Zn[Ir]‐BipyPDMSs) or Ir3+ (Ir[Ir]‐BipyPDMSs) represent flexible, stretchable, phosphorescent, and self‐healing molecular oxygen sensors. PMCs provide strong phosphorescence at λem = 595–605 nm. Zn[Ir]‐BipyPDMS with PDMS chain length of Mn = 5000 has the highest quantum yield of 9.3% and is a molecular oxygen sensor at different O2 concentrations (0–100 vol%) compared to Ir[Ir]‐BipyPDMSs. A Stern−Volmer constant is determined for Zn[Ir]‐BipyPDMS as KSV = 0.014%−1, which is similar to the reported oxygen‐sensitive iridium(III) complexes. All synthesized PMCs exhibit high elongation at break (up to 1100%) and self‐healing efficiency (up to 99%). [ABSTRACT FROM AUTHOR]

New shape‐memory networks composed of both reversible Diels–Alder covalent crosslinks and the hydrogen and π–π stacking bonds of triazine functional groups, with self‐healing properties as a result of the reversibility of these dynamic bonds were achieved from a furfuryl‐functionalized copoly(triazine‐r‐polypropylene glycol‐r‐polydimethylsiloxane), crosslinked with a maleimide end‐capped polycaprolactone and a long polycaprolactone‐based chain extender. The presence of multiple dynamic bonds, including the Diels–Alder and triazine‐derived π–π stacking and H‐bond interactions as well as the enhanced network mobility arising from polypropylene glycol, polydimethylsiloxane and polycaprolactone segments upon triggering the shape memory effect resulted in a material with high toughness (~200 MPa J−1) and efficient healing ability (with a recoveries of tensile strength and toughness after being cut and healed of 87% and 94%, respectively). Highlights: Furfuryl dichlorotriazine was coupled with PPG and PDMS forming a copolymer.The copolymer was crosslinked with PCL‐dimaleimide and PCL‐difuran extender.Multiple dynamic bonds (Diels–Alder, π–π stacking and H‐bond) were present.The network showed high toughness and good healing performance. [ABSTRACT FROM AUTHOR]

Cobaltocenium-containing (co)polysiloxanes (Cc-PDMSs) with terminal and side groups were synthesized by the reaction of catalyst-free hydroamination between ethynylcobaltocenium hexafluorophosphate and polysiloxanes comprising amino moieties as terminal and side groups. The conversion of NH2 groups in the polymers reaches 85%. The obtained (co)polysiloxanes "gelate" due to an increase in their molecular weight by approx. 30 times, when stored at room temperature over one week. "Gelated" Cc-PDMSs remain soluble in most polar solvents. The structure of Cc-PDMSs and the mechanism of "gelation" were established by 1H, 13C{1H}, 29Si{1H}, 19F{1H}, 31P{1H} nuclear magnetic resonance, infrared, ultraviolet–visible, and X-ray photoelectron spectroscopies. As determined by cyclic voltammetry, Cc-PDMSs possess redox properties (CoII/CoIII transitions at E1/2 = −1.8 and −1.3 V before and after "gelation", respectively). This synthetic approach allows to increase the molecular weights of the synthesized polysiloxanes functionalized with cobaltocenium groups easily, leading to their higher film-forming ability, which is desirable for some electronic applications. Cc-PDMSs can be utilized as redox-active polymer films in modified electrodes, electrochromic devices, redox-active coatings, and components for batteries. [ABSTRACT FROM AUTHOR]

In this work, a Pd(II)-C,N-cyclometalated complex was grafted to polysiloxanes via azide–alkyne cycloaddition. The obtained polymer–metal complex (Pd-PDMS) acts as a catalyst in the Suzuki–Miyaura reaction. Pd-PDMS was drop-casted onto a carbon fiber support, and the resulting membrane demonstrated catalytic activity in the cross-coupling reaction without yield loss after several catalytic cycles. The catalytic membrane allows for easy catalyst recycling and provides ultra-low palladium levels in Suzuki–Miyaura reaction products. [ABSTRACT FROM AUTHOR]

Experimental results for the long-term full-scale climatic testing of aviation polysulfide and VITEF-1B, VGM-L, VIKSINT U-20-99, and VGF-2M polysiloxane grade sealing materials are presented. The testing have been carried out under open conditions of humid tropical climate characterizing Wanning (Hainan Island, China) and moderately warm climate characterizing Gelendzhik. In order to analyze the reasons for decreasing elasticity and strength, the results of similar testing under the conditions of Moscow, Florida, Arizona, and Vietnam have been used. It is shown that under the influence of radiation, destruction and cross-linking reactions occur that lead to the change in the elasticity of the studied materials. [ABSTRACT FROM AUTHOR]

Poly(hydromethylsiloxane) (PHMS) was cross-linked with 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (D4Vi) in water-in-oil High Internal Phase Emulsions to form macroporous materials known as polyHIPEs. It was shown that in the process of pyrolysis under Ar atmosphere at 520 °C, the obtained polyHIPEs were converted to ceramers with high yields (82.8–88.0 wt.%). Structurally, the obtained ceramers were hybrid ceramics, i.e., they consisted of Si-O framework and preserved organic moieties. Macropores present in the polyHIPE precursors remained in ceramers. Ceramers contained also micro- and mesopores which resulted from the precursor's mass loss during pyrolysis. Total pore volume and BET specific surface area related to the existence of micro- and mesopores in ceramers depended on the PHMS: D4Vi ratio applied in polyHIPE synthesis. The highest total pore volume (0.143 cm3/g) and specific surface area (344 m2/g) were reached after pyrolysis of the precursor prepared with the lowest amount of D4Vi as compared to PHMS. The composite materials obtained after deposition of PdO nanoparticles onto ceramers followed by reduction of PdO by H2 were active and selective catalysts for phenylacetylene hydrogenation to styrene. [ABSTRACT FROM AUTHOR]

Herein, a novel, highly branched and photoresponsive polysiloxane is synthesized and studied. The polymer is photoconstructed into a single‐chain nanoparticle loaded with Nile Red and Metformin. Through the photoreversible [2+2] mechanism of the polymer's pendant coumarin moieties, the nanoparticles are de‐crosslinked, and their cargo molecules released. A study of the kinetics of release is undertaken in different solvents, providing insight into the relationship between the cargo's molecular structure and that of the polymer chain. On the whole, this report's study introduces new controlled release and cationic ring‐opening polymerization concepts while providing the first example of a single‐chain polymer nanoparticle based on a photoresponsive polysiloxane. [ABSTRACT FROM AUTHOR]

As part of this research, new halogen free organosilicon compounds were synthesized for the modification of natural fabrics. Difunctional polysiloxanes containing alkoxysilyl groups and silsesquioxane moieties in their structure were obtained by hydrosilylation or thiol-ene click reaction. Using two different reactions leading to the formation of polysiloxane derivatives, we demonstrate the influence of the chemical structure of the obtained polymers on the properties of modified cotton. The structure of the synthesized compounds was confirmed by FT-IR and NMR spectroscopy. After the synthesis of 6 different polysiloxane derivatives with different content of functional groups in their structures, they were applied to the natural fabrics in order to render them hydrophobic. The samples were modified via the dip-coating process. As a result of the research, superhydrophobic fabrics were obtained that are completely resistant to the process of repeated washing. The water repellency of the fabrics was assessed by measuring the water contact angle. The presence of the modifier on the fiber surface (before and after washing) was confirmed by FT-IR and SEM–EDS analysis. In addition, the surface of the modified fibers was examined using SEM images. [ABSTRACT FROM AUTHOR]

The investigation of thermoluminescence (TL) glow curves in liquid crystalline side chain N‐phenyl‐substituted phenyl polysiloxane hydroxamic acids (PHAs) has yielded significant insights. These polymers demonstrated TL behavior when exposed to β‐radiation between 0 and 220°C, indicating inherent luminescent properties when irradiated. Notably, a dose‐dependent relationship was observed in reported derivatized polymers; this study elucidates the diverse TL characteristics exhibited by various liquid crystalline side chain N‐phenyl‐substituted phenyl PHAs when exposed to β‐radiation. Understanding these dose‐dependent and dose‐independent behaviors enhances the knowledge of their luminescent properties and potential applications in radiation detection. [ABSTRACT FROM AUTHOR]

Cobaltocenium-containing (co)polysiloxanes (Cc-PDMSs) with terminal and side groups were synthesized by the reaction of catalyst-free hydroamination between ethynylcobaltocenium hexafluorophosphate and polysiloxanes comprising amino moieties as terminal and side groups. The conversion of NH2 groups in the polymers reaches 85%. The obtained (co)polysiloxanes “gelate” due to an increase in their molecular weight by approx. 30 times, when stored at room temperature over one week. “Gelated” Cc-PDMSs remain soluble in most polar solvents. The structure of Cc-PDMSs and the mechanism of “gelation” were established by 1H, 13C{1H}, 29Si{1H}, 19F{1H}, 31P{1H} nuclear magnetic resonance, infrared, ultraviolet–visible, and X-ray photoelectron spectroscopies. As determined by cyclic voltammetry, Cc-PDMSs possess redox properties (CoII/CoIII transitions at E1/2 = −1.8 and −1.3 V before and after “gelation”, respectively). This synthetic approach allows to increase the molecular weights of the synthesized polysiloxanes functionalized with cobaltocenium groups easily, leading to their higher film-forming ability, which is desirable for some electronic applications. Cc-PDMSs can be utilized as redox-active polymer films in modified electrodes, electrochromic devices, redox-active coatings, and components for batteries.

In this work, a Pd(II)-C,N-cyclometalated complex was grafted to polysiloxanes via azide–alkyne cycloaddition. The obtained polymer–metal complex (Pd-PDMS) acts as a catalyst in the Suzuki–Miyaura reaction. Pd-PDMS was drop-casted onto a carbon fiber support, and the resulting membrane demonstrated catalytic activity in the cross-coupling reaction without yield loss after several catalytic cycles. The catalytic membrane allows for easy catalyst recycling and provides ultra-low palladium levels in Suzuki–Miyaura reaction products.

Poly(hydromethylsiloxane) (PHMS) was cross-linked with 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (D4Vi) in water-in-oil High Internal Phase Emulsions to form macroporous materials known as polyHIPEs. It was shown that in the process of pyrolysis under Ar atmosphere at 520 °C, the obtained polyHIPEs were converted to ceramers with high yields (82.8–88.0 wt.%). Structurally, the obtained ceramers were hybrid ceramics, i.e., they consisted of Si-O framework and preserved organic moieties. Macropores present in the polyHIPE precursors remained in ceramers. Ceramers contained also micro- and mesopores which resulted from the precursor’s mass loss during pyrolysis. Total pore volume and BET specific surface area related to the existence of micro- and mesopores in ceramers depended on the PHMS: D4Vi ratio applied in polyHIPE synthesis. The highest total pore volume (0.143 cm3/g) and specific surface area (344 m2/g) were reached after pyrolysis of the precursor prepared with the lowest amount of D4Vi as compared to PHMS. The composite materials obtained after deposition of PdO nanoparticles onto ceramers followed by reduction of PdO by H2 were active and selective catalysts for phenylacetylene hydrogenation to styrene.

This study presents the results of a search for ways to prevent biodestructive processes, occurring in the natural environment of wooden architecture monuments localization. On the Sviyazhsk island since the 16th century an unique site of wooden architecture of the Volga region has been preserved. It is the Trinity Church, the only building, although rebuilt over the centuries, that has survived from the wooden medieval island-town. Climate changes, cultural tourism and living organisms activities make a significant contribution to the change in the initial state of the tree. The greatest contribution to the processes of biodamage is made by mold fungi – micromycetes. Experimental work carried out on a fragmentary sample of a structural element of the Trinity Church revealed that coating the surface of the sample with a synthetic varnish based on a mixture of linear and cyclic methylmethoxypolysiloxanes prevents the growth of microscopic fungi on the surface, among which Aspergillus niger dominates. The growth area of the sample is reduced by about 6 times compared to the untreated variant. By artificial infection of samples with spores of Aspergillus niger, Penicillus chrysogenum, Fusarium graminearum and Aspergillus puulaauensis, the growth area of varnished samples also decreases by 7 times, and the number of conidiophores, reflecting the growth of micromycetes, by 4 times. The obtained results make it possible to recommend the use of polysiloxane coatings for the protection of especially important fragments of wooden artifacts.

In this study, silane and quaternary ammonium functional methacrylate monomers were synthesized and used to construct a copolymer using an emulsion polymerization technique to control the reaction rate. The copolymer was then designed using different ratios of silane and quaternary ammonium groups to investigate the relationship between the structure and properties. The presence of the ethoxy silane group in the copolymer series provided covalent bonding through the silanol group onto cotton fabric. The presence of cationic groups also helped to cover the fabric surface. After coating the cotton textile fabric, the resistance of the dye on the fabric surface to friction was assessed and tests were conducted on washing, rubbing, water, and light fastness. Finally, the textile surfaces were investigated for their antibacterial activity against Staphylococcus aureus and Escherichia coli. It was observed that the copolymer series showed >99% killing efficiency against S. aureus but had no effect on E. coli. [ABSTRACT FROM AUTHOR]

The development of polymeric composites that possess both exceptional electromagnetic interference shielding effectiveness (EMI SE) and high absorption capacity has always been appealing, yet it continues to pose a significant challenge. To this end, we disclose a hollow and spherical shielding unit that could achieve "absorption‐reflection‐attenuation" process for incident electromagnetic (EM) wave, which was fabricated through decorating Ni nanoparticles onto rGO hollow microspheres by virtue of Pickering emulsification method followed by thermal annealing. With integrated magnetic and electric parts, the consequent shielding composite by assembling these microspheres into PDMS displayed not only a favorable EMI SE of 44 dB across the entire x‐band, but also significantly improved absorption performance that has exceeded 95% of the total SE. Moreover, the power coefficient of absorption (A) is up to 0.73 at the pyrolysis temperature of 550°C. Such admirable performance is mainly attributed to the synergistic effect of conductive rGO walls, magnetic Ni nanoparticles, as well as the unique spherical architecture, which has enabled more efficient capture and attenuation of EM waves. Herein, this research has highlighted the development of polymeric composites for high‐performance EMI shielding applications. Highlights: Reflection‐absorption‐integrated shielding compartment was designed.Decorating magnetic Ni nanoparticles onto rGO hollow microspheres.High EMI SE with enhanced absorption ability was acquired.Unique structure generating synergistic effect on EMI shielding [ABSTRACT FROM AUTHOR]

We propose to use the platinum(II) C,N‐cyclometalated complex (PCC) to catalyze the hydrosilylation and dehydrocoupling reactions of high molecular weight polysiloxanes at elevated temperatures (above 100°C). PCC was prepared via a three‐step procedure consisting of the 2‐hydrazinopyridine synthesis, its treatment with 3‐methoxy‐4‐(prop‐2‐yn‐1‐yloxy)benzaldehyde, and coupling of the obtained product with cis‐[PtCl2(CNXyl)2]. This complex exhibits thermal stability up to 150°C even at heating in air. PCC allows carrying out the cross‐linking of vinyl‐terminated polydimethylsiloxane (V‐PDMS) and polymethylhydrosiloxane (PMHS) by hydrosilylation, as well as PMHS dehydrocoupling cross‐linking at 150 and 120°C, respectively. The coupling (cross‐linking) patterns were successfully confirmed by 1H, 13C, and 29Si solid‐state NMR spectroscopy. The thermal and swelling characteristics and the transparency of the obtained silicone materials indicate the absence of aggregation of platinum particles. [ABSTRACT FROM AUTHOR]

In this study, a series of ladder‐like polysiloxanes are synthesized by introducing double‐chain Si–O–Si polymer as the backbone and the carbazole and triphenylphosphine oxide with high triplet energy as side groups. The ladder‐like structures of polysiloxanes are achieved through a controlled polymerization method that involves the monomer self‐assembly and subsequent surface‐restricted solid‐phase in situ condensation through freeze‐drying. The introduction of siloxane improves thermal stability of the polymers and inhibits the conjugation of the polymers between the side groups, leading to an increase in the triplet energy level. Therefore, all these polymers perform higher triplet energy levels than phosphorescent emitter (FIrpic). The cyclic voltammetry measurements demonstrate that the bipolar polymer exhibits a high highest occupied molecular orbital (HOMO) value of −5.32 eV, which is consistent with the work function of ITO/PEDOT:PSS, consequently facilitating hole injection. Furthermore, the incorporation of triphenylphosphine oxide promotes electron injection. Molecular simulations reveal that the frontier orbital distributions of the bipolar polymer are located on the carbazole and triphenylphosphine groups, respectively, which facilitate the transport of electrons and holes. [ABSTRACT FROM AUTHOR]

To obtain unconjugated hyperbranched polysiloxane (HBPSi), the triethoxyvinylsilane (A-151) and simple polyol compounds were used as raw materials, and two kinds of unconjugated HBPSi which the terminal group is -OH group and C=C bond were synthesized via a simply transesterification condensation, and the factors that affecting their luminescence are also further discussed. The results showed that, both of these two HBPSi exhibits excellent aggregate induced emission effect. The structure rich in π electrons or lone pair electrons in the raw materials basically maintains its original state in the polymer, and the spatial conjugation of the two leads to the luminescence of non-conjugated polymers. A large number of -OH groups in the polymer can form hydrogen bonds, and the promotion of hydrogen bonds makes the target products further gather spontaneously, which further enhances the spatial conjugation and improves the rigidity of the molecules. It can be concluded that under certain conditions, the larger steric hindrance of the molecule itself will affect the polymerization degree of the final product and the aggregation degree of the polymer molecule, while low polymerization and aggregation degree will result in higher energy required for the material to fluoresce. This study provides some reference significance for the preparation of non-conjugated luminescent materials with higher fluorescence intensity. [ABSTRACT FROM AUTHOR]

The behavior of materials against water is a key element in many practical applications. Silicones are hydrophobic by nature and can be chemically modified to become hydrophilic or highly hydrophobic, while combining intrinsic surface properties with morphological details may lead to superhydrophobic materials. Chemically modified porous silicones and their surface properties have rarely been investigated. Our aim in this study was to tune the surface properties of porous silicone materials by a combination of chemical modification and emulsion templating The porous silicones were obtained by two cross-linking reactions in toluene–water emulsion, in mild conditions: dehydrocoupling of poly(methylhydrogen)siloxane (PMHS) and dimethyl-methylhydrogensiloxane copolymers and UV-initiated thiol-ene addition on a poly(dimethyl-methylvinyl)siloxane, respectively. Apart from the pores generated by water droplets, in the first process, additional large pores appeared due to hydrogen evolution. Their size and number diminished along with the cross-linking degree; thus, the porosity was tuned by adjusting the composition of the reaction mixture. Chemical modifications were performed in situ to introduce more hydrophobic groups (hexane and trimethylsilane) or hydrophilic groups (thioethanol), modifications that were followed by FT-IR spectroscopy. The inner morphology and powder wetting behavior of the crushed samples were investigated by SEM, tensiometry analyses, and contact angle measurements. The materials showed morphological particularities and surface properties that spanned from hydrophilic to superhydrophobic with lotus or petal effects. [ABSTRACT FROM AUTHOR]

Silicon oxycarbides synthesized through a conventional polymeric route show characteristic nanodomains that consist of sp2 hybridized carbon, tetrahedrally coordinated SiO4, and tetrahedrally coordinated silicon with carbon substitution for oxygen, called "mixed bonds." Here we synthesize two preceramic polymers possessing both phenyl substituents as unique organic groups. In one precursor, the phenyl group is directly bonded to silicon, resulting in a SiOC polymer-derived ceramic (PDC) with mixed bonding. In the other precursor, the phenyl group is bonded to the silicon through Si-O-C bridges, which results in a SiOC PDC without mixed bonding. Radial breathing-like mode bands in the Raman spectra reveal that SiOC PDCs contain carbon nanoscrolls with spiral-like rolled-up geometry and open edges at the ends of their structure. Calorimetric measurements of the heat of dissolution in a molten salt solvent show that the SiOC PDCs with mixed bonding have negative enthalpies of formation with respect to crystalline components (silicon carbide, cristobalite, and graphite) and are more thermodynamically stable than those without. The heats of formation from crystalline SiO2, SiC, and C of SiOC PDCs without mixed bonding are close to zero and depend on the pyrolysis temperature. Solid state MAS NMR confirms the presence or absence of mixed bonding and further shows that, without mixed bonding, terminal hydroxyls are bound to some of the Si-O tetrahedra. This study indicates that mixed bonding, along with additional factors, such as the presence of terminal hydroxyl groups, contributes to the thermodynamic stability of SiOC PDCs.

Recently, the photovoltaic technology has become very popular as a means to produce renewable energy. One of the problems that are still unsolved in this area of the industry is that photovoltaic panels are subject to a significant loss of efficiency due to the accumulation of dust and dirt. In addition, during the winter season, the accumulation of snow and ice also reduces or stops the energy production. The current methods of dealing with this problem are inefficient and pollute the environment. One way with high potential to prevent the build-up of dirt and ice is to use transparent coatings with self-cleaning and icephobic properties. In this work, the chemical modification of an epoxy–silicone hybrid resin using dually functionalized polysiloxanes was carried out. The icephobic properties (ice adhesion and freezing delay time of water droplets), hydrophobic properties (water contact angle, contact angle hysteresis, and roll-off angle), average surface roughness, and optical properties were characterized. It can be concluded that the performed chemical modification resulted in a significant improvement of the icephobic properties of the investigated coatings: ice adhesion decreased by 69%, and the freezing delay time increased by 17 times compared to those of the unmodified sample. The polysiloxanes also caused a significant reduction in the contact angle hysteresis and roll-off angle. The chemical modifications did not negatively affect the optical properties of the coatings, which is a key requirement for photovoltaic applications. [ABSTRACT FROM AUTHOR]

The known ferrocenyl-containing silicone materials have redox activity and electrical conductivity at the level of antistatic materials, but they are incapable of self-healing due to their irreversible cross-linking, which significantly reduces their application area. The development of novel self-healing ferrocenyl-containing silicone rubbers (FSRs) is a promising area of research that extends the possibilities of their application as protective coatings. In this work, a new method was developed to synthesize FSRs with different ferrocenyl unit content (25 and 50 mol.%) by anionic copolymerization of cyclic octamethylcyclotetrasiloxane (D4), cyclic tetraferrocenyl-substituted 1,3,5,7-tetramethyltetrasiloxane (Fc4D4), and bicyclic cross-linking agent (bis-D4). The optimal concentrations of the cross-linking agent and ferrocenyl-substituted unit content for FSRs are 5 wt.% and 25 mol.%, respectively. The FSRs exhibit tensile strength and elongation at break up to 0.1 MPa and 215%. The FSRs possess both self-healing at room and/or elevated temperatures (100 °C) and redox activity (Fc/Fc+ transformations at E0 = 0.43 V) and conductivity at the antistatic level (ca. 10−10–10−11 S·cm−1). The thermal properties of the FSRs were studied. The proposed approach is relevant for the creation of new functional silicone materials as flexible, self-healing, and antistatic protective coatings. [ABSTRACT FROM AUTHOR]

Accurate chemical analysis of small samples of fine powders in the Si–O–C–H system is challenging. We present a comparison of analysis by X-ray photoelectron spectroscopy (XPS) and combustion analysis, validating XPS as an accurate and simple methodology for Si, C, and O analysis to give bulk and not just surface compositions. The XPS analyses are supported by showing consistency in thermochemical calculations of heats of formation based on high temperature oxide melt solution calorimetry. However, because XPS is not suitable for quantitation of hydrogen, it must be combined with other techniques for samples with substantial H content.

Silica aerogel microspheres show great potential in various fields as fillings in different materials. It is important to diversify and optimize the fabrication methodology for silica aerogel microspheres (SAMS). This paper presents an eco-friendly synthetic technique for producing functional silica aerogel microspheres with a core–shell structure. Mixing silica sol with commercial silicone oil containing olefin polydimethylsiloxane (PDMS) resulted in a homogeneous emulsion with silica sol droplets dispersed in the oil. After gelation, the droplets were transformed into silica hydrogel or alcogel microspheres and coated with the polymerization of the olefin groups. Microspheres with silica aerogel as their core and polydimethylsiloxane as their shell were obtained after separation and drying. The sphere size distribution was regulated by controlling the emulsion process. The surface hydrophobicity was enhanced by grafting methyl groups onto the shell. The obtained silica aerogel microspheres have low thermal conductivity, high hydrophobicity, and excellent stability. The synthetic technique reported here is expected to be beneficial for the development of highly robust silica aerogel material. [ABSTRACT FROM AUTHOR]

A new type of oligophenyl-siloxane was prepared by using a precursor and a route which are non-conventional. The synthesis iniciated with the obtention of Octakis(chloro-calcium-oxy)cyclotetrasilicate by depolymerization of Wollastonite in molten CaCl2. The cyclotetrasilicate was silylated with phenyl-chloro-diethoxy-silane originating a liquid siloxane whose molecules presented a cross-like structure (C-PhS). The crosses were subjected to hydrolysis and condensation under mild conditions promoting their crosslinking and the formation of oligomeric solids (C-OPhS). It was corroborated that, in the solid state, oligomers self-assemble through hydrogen bonding and/or π-π stacking due to their OH and phenyl groups. Because of this supramolecular structure formation, it was possible to find the crossbar width which varied between 10.8 and 11.4 Å. [ABSTRACT FROM AUTHOR]

In this paper, a series of novel carbazole-based polysiloxane oligomers: P(CzVinyl11Siloxane2), P(CzVinyl21Siloxane2), and P(CzVinyl11Siloxane3) with high refractive index (RI) containing the linear and/ or branched structures with vinyl and carbazole reactive moieties have been presented to the literature for optoelectronic applications. The polysiloxane oligomers were synthesized by an acid-catalyzed sol–gel condensation reaction of alkoxysilane monomers (carbazole-dimethoxysilane (Cz-2SiOCH3) and vinyl-(di- or tri-methoxy)silanes (VMDMS or VTMS)) in the presence of trimethylmethoxysilane (SiMe) after a photoinitiated thiol-ene reaction was performed to obtain the compound Cz-2SiOCH3. The structural confirmations were made using FT-IR, 1H NMR, and 13C NMR spectroscopies. In addition, a 29Si NMR study was performed to elucidate the nature of the siloxane structure of P(CzVinyl11Siloxane2). The refractive indices of the polysiloxane oligomers were between 1.6028 and 1.5923 as high values by varying the linear or branched structures. DSC analyzes revealed that the glass transition temperatures of P(CzVinyl11Siloxane2), P(CzVinyl21Siloxane2), and P(CzVinyl11Siloxane3) were -11 °C, -5 °C and -39 °C, respectively. Then, the polysiloxane oligomers were photopolymerized and their structural changes were observed by spectroscopic techniques. The photopolymerized polysiloxane oligomers with maintained and/ or enhanced refractive index values (between 1.6132 and 1.5719) showed very good transparency between 86.11% and 81.33% at 600 nm by the spin coating films. The novel carbazole-based polysiloxane oligomers would be useful chemical products or intermediates for the development of optical materials applied in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Background: Scar formation is undesirable both cosmetically and functionally. It shows that silicone gel is effective in preventing and improving scars formed due to a wound formation after injury. Objectives: This study investigates whether a silicone gel composition based on a novel concept of infusing a biologically active material such as hyaluronic acid and/or salts with various polysiloxane derivatives in a specific proportion to achieve desired viscosity range and their action has a synergistic beneficial effect on skin scar after injury. Methods: We have developed a topical gel utilizing a combination of emulsifiers, sodium hyaluronate, polysiloxane, and its derivatives. The method of preparation comprises mixing of aqueous phase dispersion and polysiloxanes blend under stirring at room temperature. Results: It results in the formation of a homogenous smooth gel formulation. The developed topical gel formulation was characterized for physicochemical properties, rheology, stability, and anti‐scar activity in Wistar rats. It was found that the developed formulation system consists of desirable attributes for skin applications. In vivo investigation of developed polysiloxane gel formulation for anti‐scar activity shown promising outcomes compared to marketed product (Kelo‐cote scar gel). Furthermore, a histopathology study of healed skin tissues observed the formation of microscopic skin structures compared to the Kelo‐cote scar gel. Conclusions: It indicates that the combination of polysiloxanes and sodium hyaluronate resulting an improvement in anti‐scar activity compared to the marketed product containing polysiloxanes alone. [ABSTRACT FROM AUTHOR]

Accurate chemical analysis of small samples of fine powders in the Si–O–C–H system is challenging. We present a comparison of analysis by X-ray photoelectron spectroscopy (XPS) and combustion analysis, validating XPS as an accurate and simple methodology for Si, C, and O analysis to give bulk and not just surface compositions. The XPS analyses are supported by showing consistency in thermochemical calculations of heats of formation based on high temperature oxide melt solution calorimetry. However, because XPS is not suitable for quantitation of hydrogen, it must be combined with other techniques for samples with substantial H content. [ABSTRACT FROM AUTHOR]

Silicone elastomers are usually produced via addition or condensation curing by means of platinum‐ or tin‐based catalysis. The employed catalysts remain in the final rubber and cannot be recovered, thus creating various economic and environmental challenges. Herein, a light‐mediated curing method using multifunctional silacyclopropenes as crosslinker structures was introduced to create an effective alternative to the conventional industrial crosslinking. To evaluate the potential of the photoreaction a model study with small monofunctional silirenes was conducted. These investigations confirmed the required coupling reactivity upon irradiation and revealed an undesired rearrangement formation. Further optimization showed the reaction selectivity to be strongly influenced by the substitution of the three‐membered ring system and the reaction temperature. The synthesis of multifunctional silirenes was described based on the most suitable model compound to create active crosslinker scaffolds for their application in silicone curing. This photo‐controlled process produces catalyst and additive free elastomers from liquid silicones, including hydride‐, hydroxy‐, or vinyl terminated polydimethylsiloxanes. [ABSTRACT FROM AUTHOR]

In this paper, we designed and synthesised three H-shaped liquid crystal monomers ABOP-n (n = 4,6,8) and a straight-chain liquid crystal monomer M. Then, we used three H-shaped liquid crystal monomers as crosslinking agents, which were graft-copolymerised with M and polymethylhydrosiloxane (PMHS), respectively, to synthesise three series of liquid crystal elastomers P1–P3. The products were structurally well characterised by elemental analysis, 1HNMR, and FT-IR. The phase behaviours were investigated using the polarising microscope (POM) and differential scanning calorimetry (DSC). The results showed that ABOP-8, ABOP-6, ABOP-4 and M were thermotropic enantiotropic nematic liquid crystals, exhibiting schlieren texture during heating, and spherulite texture and schlieren texture during cooling. The photochemical properties of H-shaped liquid crystal monomers were preliminarily studied by UV-Vis spectra, and it was found that they have good photosensitivity. Both the P1–P3 series were typical non-crystalline polymers with anisotropic coloured textures. With the increase of crosslinking monomer content, the glass transition temperature of the P1–P3 series both increased, while the isotropic temperature showed a trend of first decreasing and then increasing. [ABSTRACT FROM AUTHOR]

Anti-icing coatings have provided a very good alternative to current, uneconomic, active deicing methods, and their use would bring a number of significant benefits to many industries, such as aviation and energy. Some of the most promising icephobic surfaces are those with hydrophobic properties. However, the relationship between hydrophobicity and low ice adhesion is not yet clearly defined. In this work, chemical modification of an epoxy gelcoat with chemical modifiers from the group of double organofunctionalized polysiloxanes (generally called multifunctionalized organosilicon compounds (MFSCs)) was applied. The anti-icing properties of manufactured coatings were determined by means of measurements of shear strength between the ice layer and the modified surface, conducted using a tensile machine. In the work, tests were also performed on the roughness, wettability, and durability of the properties in an aging chamber. It was found that the performed modifications of the coating's chemical composition by the addition of polysiloxanes enabled us to reduce ice adhesion by 51% and to increase the water contact angle by 14% in comparison to the neat gelcoat. A reduction in ice adhesion was also observed with the increasing water contact angle and with decreasing surface roughness. In addition, only one modification recorded an increase in ice adhesion after exposure in the aging chamber. [ABSTRACT FROM AUTHOR]

Novel spherically shaped organosilica materials with (propyl)ethylenediamine groups were obtained via a modified one-pot Stöber co-condensation method. The porosity of these materials was tuned with the controlled addition of three silica monomers acting as structuring agents (tetraethoxysilane and bridged silanes with ethylene and phenylene bridges). The morphologies and structures of the synthesized materials were studied by SEM, DRIFT spectroscopy, CHNS elemental analysis, low-temperature nitrogen adsorption–desorption, and electrokinetic potential measurements. Their sizes were in the range of 50 to 100 nm, depending on the amount of structuring silane used in the reaction. The degree of the particles' agglomeration determined the mesoporosity of the samples. The content of the (propyl)ethylenediamine groups was directly related with the amount of functional silane used in the reaction. The zeta potential measurements indicated the presence of silanol groups in bissilane-based samples, which added new active centers on the surface and reduced the activity of the amino groups. The static sorption capacities (SSCs) of the obtained samples towards Cu(II), Ni(II), and Eu(III) ions depended on the porosity of the samples and the spatial arrangement of the ethylenediamine groups; therefore, the SSC values were not always higher for the samples with the largest number of groups. The highest SSC values achieved were 1.8 mmolCu(II)/g (for ethylene-bridged samples), 0.83 mmolNi(II)/g (for phenylene-bridged samples), and 0.55 mmolEu(III)/g (for tetraethoxysilane-based samples). [ABSTRACT FROM AUTHOR]

Polysiloxanes and materials based on them (silicone materials) are of great interest in optoelectronics due to their high flexibility, good film-forming ability, and optical transparency. According to the literature, polysiloxanes are suggested to be very promising in the field of optoelectronics and could be employed in the composition of liquid crystal devices, computer memory drives organic light emitting diodes (OLED), and organic photovoltaic devices, including dye synthesized solar cells (DSSC). Polysiloxanes are also a promising material for novel optoectronic devices, such as LEDs based on arrays of III–V nanowires (NWs). In this review, we analyze the currently existing types of silicone materials and their main properties, which are used in optoelectronic device development. [ABSTRACT FROM AUTHOR]

The increasing range of applications of silicone material requires improvements in their properties to withstand rigorous conditions. Clay minerals are attractive reinforcement nanofillers that are used in polymer matrices. They improve numerous properties of the obtained clay-polymer nanocomposites (CPNs). This work is the first review devoted to CPNs in which the polymer matrix is polysiloxanes. The incorporation of clay minerals into polysiloxanes is considered to be an exciting route for creating new and innovative nanocomposites with improved performance properties that can meet the growing demand for advanced materials used in various industries. This review describes how different clay minerals, both natural and synthetic, have been introduced into polysiloxane systems. The characteristics of the obtained nanocomposites, their properties, and the possibilities of their application are discussed. Basic information on polysiloxanes and their applications, methods of cross-linking polysiloxanes, and classification of clay minerals, as well as basic methods of modifying clay minerals used in polysiloxane matrices, were discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

The applications of epoxy resins are restricted in certain areas due to their brittleness, while improving the epoxy toughness always compromises their strength. We reported a phenyl, propyl polysiloxane modified epoxy resins with excellent tensile strength and toughness before. In this study, the mechanism of strengthening and toughening are studied and elaborated. Compared to cured EP resin (EP), cured P/E resin (P/E20) significantly improved the tensile strength, elongation at break, impact strength, and critical strain energy release rate (G Ic) by 45 %, 248 %, 18 %, and 512 %, respectively. Fracture analysis of the P/E20 revealed the appearance of parabolic markings, typical and convincing evidence of ductile fracture, indicating good toughness of the resin. AFM height and Young's modulus plots reveal the complex details of the dimples and the co-continuous phases, which provide the strong evidence to explain the reinforcement and toughening mechanism. [Display omitted] • The tensile strength and toughness (G Ic) of DGEBA were simultaneously enhanced by 45 % and 512 %, respectively. • Investigations by AFM into the cured modified resin revealed the presence of co-continuous phases. • The 3D morphology and modulus of the dimples, a prominent toughness feature, were thoroughly illustrated through AFM. • The strengthening and toughening mechanism of DGEBA was revealed. [ABSTRACT FROM AUTHOR]

Blending is an effective way to improve properties of rubbers and develop new materials, so more than 75 % of the rubber consumption in the world is rubber blend. However, blending of thermoplastic elastomers has not yet been emphasized, and few successful examples have been reported. The main challenge for blend systems is compatibility of two components. Herein, a series of (polydimethylsiloxane-based PU)-g-(poly (propylene glycol)-based PU) ((PDMS-PU)-g-(PPG-PU)) graft copolymers with different graft chain lengths and hard segment contents (HSC) were synthesized and utilized as compatibilizers of PDMS-PU/PPG-PU blends. The influence of the structure of compatibilizers on the morphology of blends was investigated, and the compatibilization mechanism was proposed. With the solubilization, the phase structure of blends transforms from "droplet-in-matrix" morphologies to co-continuous ones, and the average size of PPG-PU dispersed phase decreases from 3.5 ± 0.45 μm to 230 ± 60 nm. This is the first time that thermoplastic PDMS-PU/PPG-PU blends with co-continuous structures have been successfully prepared. The properties of blends exhibit synergistic effects. For example, they show high tensile strength of PPG-PU in mechanical properties and unique properties of PDMS in dynamic mechanical properties, weather resistance, water resistance and biocompatibility. In addition, strain sensors were fabricated by introducing carbon nanotubes (CNTs) into the blends, which demonstrated remarkable sensing capability for diverse human body motions. [Display omitted] • By adjusting the structural parameters of the compatibilizers, PDMS-PU/PPG-PU blends are transformed to a co-continuous morphology structure, with the average size of dispersed phase reaching a hundred-nanometer scale. • The tensile strength of blends with co-continuous structure increases by 1.3 times in comparison to that of blends without compatibilizers. • The blends with co-continuous structure exhibit high tensile strength of PPG-PU in mechanical properties and unique properties of PDMS in thermal resistance, weather resistance, water resistance and biocompatibility. • The blends are expected to be applied in flexible sensors and wearable devices. [ABSTRACT FROM AUTHOR]

The synthesis and properties of side chain polysiloxane hydroxamic acids have been described. The N-p substituted phenyl hydroxamic acids were synthesized by reacting p - allyloxy benzoyl chloride and acryloyloxy sebacoyl chloride with N-arylhydroxylamines in toluene medium, rendered basic with aqueous suspension of sodium bicarbonate at 0 °C or lower. The synthesized N -phenyl substituted hydroxamic acids were attached to poly(methylhydrosiloxane) via hydrosilylation reaction in the presence of platinum catalyst The polysiloxane hydroxamic acids were characterized by melting point, FT – IR, NMR and Mass spectral techniques. The liquid crystalline behaviour of the side chain polysiloxane hydroxamic acids with allyloxy and acryloylsebacoyloxy spacer have been studied by optical. polansed microscopy and differential scanning calorimetry. Side chain liquid crystalline polysiloxane hydroxamic acids with allyloxy spacer (N-p substituted phenyl p-[(3-polysiloxane propyloxy) benzo] hydroxamic acids, (PHA – 1 to PHA −4) show nematic phases, while the second series with acryloylsebacoyloxy spacer (N-p-substituted phenyl (3-polysiloxane propanone) octyl carbonyloxy hydroxamic acids, (PHA – 5 to PHA – 8) show nematic as well as smectic phases. The liquid crystalline behaviour of the side chain polysiloxane hydroxamic acids with allyloxy and acrylsebacoyloxy spacer have been studied. [Display omitted] • Polysiloxane hydroxamic acids with an allyloxy spacer exhibit nematic liquid crystalline behaviour. The presence of the spacer shows nematic phase. • Polysiloxane hydroxamic acids with an acryloylsebacoyloxy spacer display both smectic and nematic phases. The acryloylsebacoyloxy group shows different behaviour. • The introduction of polar end groups (chlorine, bromine, iodine) in PHA 2, 3, 4, and PHA 6, 7, 8 induces the nematic phase. These polar groups enhance molecular alignment and contribute to liquid crystalline behaviour. • The orientation of the central dipole within side chain polysiloxane hydroxamic acids is crucial for achieving liquid crystalline properties. • A hydroxamic acid group as a side chain is an effective molecular design strategy. It leads to better-organized mesophases with lower transition temperatures, resulting in room temperature liquid crystalline behaviour. [ABSTRACT FROM AUTHOR]

The behavior of materials against water is a key element in many practical applications. Silicones are hydrophobic by nature and can be chemically modified to become hydrophilic or highly hydrophobic, while combining intrinsic surface properties with morphological details may lead to superhydrophobic materials. Chemically modified porous silicones and their surface properties have rarely been investigated. Our aim in this study was to tune the surface properties of porous silicone materials by a combination of chemical modification and emulsion templating The porous silicones were obtained by two cross-linking reactions in toluene–water emulsion, in mild conditions: dehydrocoupling of poly(methylhydrogen)siloxane (PMHS) and dimethyl-methylhydrogensiloxane copolymers and UV-initiated thiol-ene addition on a poly(dimethyl-methylvinyl)siloxane, respectively. Apart from the pores generated by water droplets, in the first process, additional large pores appeared due to hydrogen evolution. Their size and number diminished along with the cross-linking degree; thus, the porosity was tuned by adjusting the composition of the reaction mixture. Chemical modifications were performed in situ to introduce more hydrophobic groups (hexane and trimethylsilane) or hydrophilic groups (thioethanol), modifications that were followed by FT-IR spectroscopy. The inner morphology and powder wetting behavior of the crushed samples were investigated by SEM, tensiometry analyses, and contact angle measurements. The materials showed morphological particularities and surface properties that spanned from hydrophilic to superhydrophobic with lotus or petal effects.

Fluorescent liquid crystal polymers have attracted much attention because of the combination of fluorescence, liquid crystallinity and processability. In this study, we designed and synthesised two series of photoluminescent cholesteric liquid crystal polysiloxanes, which contained cholesterol mesogens and fluorescein methyl ester with different side chain lengths. The chemical structures and liquid crystal properties of the polymers were investigated by the usual methods. The photoluminescent property were characterised by fluorescence spectroscopy. At the same time, the effects of the lengths of the fluorescent group chains on the liquid crystal and fluorescence properties of the polymers were studied. The results showed that the synthesised polymers possessing very good fluorescent and liquid crystal properties, which may has certain practical value and application prospect. [ABSTRACT FROM AUTHOR]

In order to eliminate the numerous limitations in application of cotton fibers, we designed and made a protective coating that changes many features of these material (such as water repellency or reducing the rate of thermal degradation), but does not change its natural flexibility and macroscopic appearance. The coating we developed consists a UV-crosslinked polysiloxanes together with organophosphates. The coating preparation process takes only a few minutes and takes place easily at room temperature. Even a very subtle layer of such a coating makes the fabric highly hydrophobic, and with greater occupancy, it significantly slows down thermal degradation and reduces the flammability of fabrics. A very interesting phenomenon observed by us is also the fact that the thicker the coating layer, the worse hydrophobic properties have been observed. The resulting coating is resistant to washing with both clean water and water with detergents., Competing Interests: Declaration of competing interest The authors of the publication titled: “Quickly UV-Curing Protective Coating for Cotton Fabrics” declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

In the present paper, the effect of gallium β-oxide introduced into the polydimethylsiloxane elastomer on the electrical properties of the composite material is investigated. The dependence of the electrical resistance of the composition on the change in the specific volume electrical conductivity on the content of gallium oxide is established experimentally and the percolation point is determined. The percolation point is 21%, which is slightly higher than the theoretical value calculated by the Monte Carlo method and is 16%. The temperature dependence of the electrical resistance of the composition on the content of the semiconductor filler in the binder is determined. The dielectric characteristics of the material, such as the tangent of the dielectric loss angle and the permittivity, are studied using the waveguide method on a laboratory stand based on a precision measuring line P1-20. The dielectric characteristics are calculated by changing the displacement of the standing wave nodes in the waveguide when a dielectric is placed in it using the MathCAD program. An experiment to determine the tangent of the dielectric loss angle in the entire X-band from 8 GHz to 12 GHz has shown that the introduction of gallium oxide leads to an increase in the dielectric losses in the composition. Additional dielectric losses in the composition occur with increasing frequency. The dielectric characteristics are significantly degraded when the filler content exceeds 20% (by volume). The influence of the filler on the radio-transparent and radio-absorbing properties of the polymer composition in the centimeter microwave range is studied. The results of the work can be applied in various sectors of the national economy, including radio electronics, microwave technology and medical technology to partially reduce the background of electromagnetic radiation.

Recently, the photovoltaic technology has become very popular as a means to produce renewable energy. One of the problems that are still unsolved in this area of the industry is that photovoltaic panels are subject to a significant loss of efficiency due to the accumulation of dust and dirt. In addition, during the winter season, the accumulation of snow and ice also reduces or stops the energy production. The current methods of dealing with this problem are inefficient and pollute the environment. One way with high potential to prevent the build-up of dirt and ice is to use transparent coatings with self-cleaning and icephobic properties. In this work, the chemical modification of an epoxy–silicone hybrid resin using dually functionalized polysiloxanes was carried out. The icephobic properties (ice adhesion and freezing delay time of water droplets), hydrophobic properties (water contact angle, contact angle hysteresis, and roll-off angle), average surface roughness, and optical properties were characterized. It can be concluded that the performed chemical modification resulted in a significant improvement of the icephobic properties of the investigated coatings: ice adhesion decreased by 69%, and the freezing delay time increased by 17 times compared to those of the unmodified sample. The polysiloxanes also caused a significant reduction in the contact angle hysteresis and roll-off angle. The chemical modifications did not negatively affect the optical properties of the coatings, which is a key requirement for photovoltaic applications.

Blue‐emitting thermally activated delayed fluorescence (TADF) polymers are still in demand for high‐efficiency display materials. Through‐space charge transfer (TSCT) strategy is promising for keeping color purity of blue‐emitting polymers with nonconjugated main chains. It is, however, hard to synthesize copolymers with well‐dispersed donors or acceptors utilizing traditional polyethylene backbones via radical polymerization. Herein, two series of blue‐emitting polysiloxane with TADF properties, random and order‐controlled copolysiloxanes, are successfully designed and synthesized and their photophysical properties are investigated and compared in detail. All of them display short prompt and delay fluorescence lifetimes and a very fast reverse intersystem crossing (RISC) rate of 107 s−1. Compared with random copolysiloxanes, acceptors are well separated by donors for order‐controlled copolysiloxanes, which exhibit the faster RISC processes and the higher photoluminescence quantum yield. Therefore, the order‐controlled architecture provides a guide for improving light‐emitting efficiency of TSCT‐type TADF polymers. [ABSTRACT FROM AUTHOR]

Donor–acceptor Stenhouse adducts (DASAs) are a rapidly emerging class of visible light‐activated photochromes and DASA‐functionalized polymers hold great promise as biocompatible photoresponsive materials. However, the photoswitching performance of DASAs in solid polymer matrices is often low, particularly in materials below their glass transition temperature. To overcome this limitation, DASAs are conjugated to polydimethylsiloxanes which have a glass transition temperature far below room temperature and which can create a mobile molecular environment around the DASAs for achieving more solution‐like photoswitching kinetics in bulk polymers. The dispersion of DASAs conjugated to such flexible oligomers into solid polymer matrices allows for more effective and tunable DASA photoswitching in stiff polymers, such as poly(methyl methacrylate), without requiring modifications of the matrix. The photoswitching of conjugates with varying polymer molecular weight, linker type, and architecture is characterized via time‐dependent UV–vis spectroscopy in organic solvents and blended into polymethacrylate films. In addition, DASA‐functionalized polydimethylsiloxane networks, accessible via the same synthetic route, provide an alternative solution for achieving fast and efficient DASA photoswitching in the bulk owing to their intrinsic softness and flexibility. These findings may contribute to the development of DASA‐functionalized materials with better tunable, more effective, and more reversible modulation of their optical properties. [ABSTRACT FROM AUTHOR]

PDMS telechelics are important both in industry and in academic research. They are used both in the free state and as part of copolymers and cross-linked materials. At present, the most important, practically used, and well-studied method for the preparation of such PDMS is diorganosiloxane ring-opening polymerization (ROP) in the presence of nucleophilic or electrophilic initiators. In our brief review, we reviewed the current advances in the field of obtaining polydiorganosiloxane telechelics and monofunctional PDMS, as well as well-organized branching centers by the ROP mechanism and catalytic rearrangement, one of the first and most important reactions in the polymer chemistry of silicones, which remains so at the present time. [ABSTRACT FROM AUTHOR]