Polysiloxane Backbone Research Articles

In Situ Hybrid Si/F Polymeric Network Electrolyte with Dual Interfacial Stability for High‐Voltage Lithium Metal Batteries

AbstractHigh‐voltage lithium‐metal batteries (LMBs) are promising for energy storage applications but suffer from poor electrochemical window of solid polymer electrolytes (SPEs), which are difficult to achieve via a single polymeric functionality. Herein, a hybrid Si/F‐based polymeric 3D network is reported bearing polysiloxane backbone with fluorinated pendants to tune the highest occupied molecular orbital (HOMO)/the lowest unoccupied molecular orbital LUMO energies, thermodynamically expanding intrinsic electrochemical window of solid polymer electrolyte (SPE). Meanwhile, the hybrid Si/F functionalities with high fluorine abundance is identified to furnish dual interfacial kinetic stability at both anode and cathode interfaces with stabilized solid electrolyte interface (SEI) and cathode electrolyte interface (CEI), respectively. As a result, stable cycling in solid‐state high‐voltage LMBs is achieved up to an ultrahigh operating voltage of 4.9 V. Furthermore, it shows that in situ blending the Si/F SPE with eutectic electrolytes (EE) to form a non‐flammable gel polymer electrolyte can mitigate parasitic reactions of EE against metallic Li anode and achieve highly reversible charge–discharge cycling from 4.2 to 4.8 V at 25 °C.

СИНТЕЗ И ИССЛЕДОВАНИЕ УСТОЙЧИВЫХ К САМОКОНДЕНСАЦИИ ЧАСТИЦ КРЕМНЕЗЁМА С ПОЛИОКСИЭТИЛЕНОВЫМИ ОТВЕТВЛЕНИЯМИ

Surface modification of silicon oxide particles with oligomers or polymers is gaining popularity. Alkoxysilanes and hydroxyl-containing compounds can be used for adsorption interaction with surface hydroxyl groups of silicon dioxide. Interaction processes of alkoxysilanes are based on sol-gel synthesis reactions and, most often, tetraethoxysilane (TEOS) is used as a silane. This reaction is the basis for the preparation of silica gels, xerogels and aerogels. This method holds promise for the production of segregation-resistant organosubstituted silica particles. Alkoxysilanes react very slowly with water and acidic or basic catalysts are used to accelerate the hydrolysis reaction of silanes. Self-segregation resistant polyoxyethylene glycol (PEG) substituted silica particles (ASIP-K) were previously synthesised using potassium diethylene glycolate (DEG-K) as a catalyst of alkaline nature. The preparation of ASIP-K was based on the reactions of hydrolysis of TEOS, condensation of the resulting silanol groups and subsequent transesterification with polyoxyethylene glycol of the remaining ethoxysilane substituents. The peculiarity of the ASIP-K structure is the existence of silica in cubic form. The rate and mechanism of the reaction was controlled not only by the amount of catalyst but also by the water content, which was returned to the system after each act of condensation of the silanol groups. This reaction was very slow and the synthesis of ASIP-K was carried out for more than ten hours. When potassium or sodium hydroxides were used instead of DEG-K, the rate of the condensation reaction of silanol groups exceeds the rate of the transesterification reaction involving PEG. Therefore, only silica gel was formed under these conditions. Due to the existing problem, copper (II) chloride was used as a catalyst in the present work for the gel-silica gel process involving PEG and TEOS. The chemical structure features of the self-segregation resistant substituted polyoxyethylene glycol substituted silica (ASIP-Cu) obtained at different CuCl2 contents were investigated. The structure features of ASIP-Cu were studied using IR spectroscopy, 1H NMR and 29Si NMR spectroscopy, thermogravimetric analysis, viscosity, density, particle size measurements and surfactant property studies. It is shown that as the CuCl2 content increases during the synthesis of ASIP-Cu, the possibility of forming the silica core in cubic form decreases, and the polysiloxane backbone becomes linear. The increase of CuCl2 content up to 0.1-0.5 wt.% leads to coordination binding of polyoxyethylene glycol branches in the ASIP-Cu-0.5 composition by Cu(II) ions.

A distinct structure of TiC for electromagnetic interference shielding and thermal stability of SiTiOC ceramic nanocomposites

Materials capable of thermal stability electromagnetic interference (EMI) shielding have practical significance in the fields of aerospace. In this paper, a brand-new polymer-derived SiTiOC ceramic nanocomposites with tubular carbon was designed. The titanium atoms were uniformly introduced into the polysiloxane backbone by the transesterification between tetrabutyl titanate and silanol prepolymer, leading to excellent thermal stability properties. By controlling the pyrolysis temperature, a distinct structure of TiC was formed between the amorphous SiTiOC matrix and free carbon phase for enhanced electromagnetic interference shielding performance. More conductive paths were established, and the TiC structure initiated interfacial polarization and space charge polarization, contributing to the improvement of the dielectric loss and relaxation phenomena. Simultaneously, a total electromagnetic interference shielding efficiency of 27.85 dB at the entire X-band was reported for SiTiOC ceramic nanocomposites. A maximum SET of 38.59 dB was examined at around 12 GHz, suggesting that over 99.99% of the electromagnetic waves were shielded. The SiTiOC ceramic nanocomposites exhibited outstanding prospects in thermal stability electromagnetic interference shielding application in a severe environment.

Influence of Concentration of Thiol-Substituted Poly(dimethylsiloxane)s on the Properties, Phases, and Swelling Behaviors of Their Crosslinked Disulfides

A simple, efficient procedure has been employed to effect intra- and inter-chain crosslinking of two commercially available thiolated poly(dimethylsiloxane) copolymers (T-PDMS) with 4–6% or 13–17% of mercaptopropyl side-chains. The thiol functional groups were converted to disulfides (D-PDMS) in chloroform solutions of I2. Importantly, the conditions employed avoid over-oxidation to other types of sulfur-containing species, and the concentration of T-PDMS during the crosslinking reaction dictated the rheological properties and liquid or solid nature of the D-PDMS. The procedure for obtaining the crosslinked copolymers is simpler than other approaches in the literature used to crosslink polysiloxane backbones and to modulate their properties. By changing the concentration of T-PDMS during the treatment with I2, the degree of intra- and inter-chain crosslinking can be controlled (as assessed qualitatively by the solid or liquid nature of the products and their viscoelastic properties). For each of the T-PDMS materials, there is a concentration threshold, above which products are solids, and below which they are oils. Liquid and solid materials were characterized using 1H and 13C solution-state and 13C solid-state NMR spectroscopy, respectively. They indicate greater than 90% conversion of thiols to disulfides in the presence of excess I2. The rheological behavior of the liquid products, solvent swelling ability of solid products, and the thermal stability of the reactants and products are described. Furthermore, the solid products exhibit some of the highest swelling values reported in the literature for poly(dimethylsiloxane) (PDMS) materials. As assessed by thermal gravimetric analyses, the disulfide-crosslinked materials are more stable thermally than the corresponding thiols.

Main-chain modified polysiloxane towards ratiometric fluorescent probes for dynamic visualization of ClO-/GSH oxidation reduction fluctuations in vivo

Redox homeostasis contributing to the maintenance of normal cellular physiological states. On the contrary, off-kilter redox as a resolution member in the production of cardiovascular disease, rheumatoid arthritis, and even cancer. To date, a few reports have focused on ratiometric sustainable assays for ClO- and GSH cycling due to the headache of transient reactivity, ultra-low concentrations and short lifetimes. However, methods for the design of ratiometric fluorescent probes also need to be further expanded. In this paper, we present a novel approach to the construction of ratiometric fluorescent probes via controlled modification of polysiloxane backbones. We aimed at the controlled assembly of a biocompatible, more pliable and stable “Si-O-Si” bridging framework, “red gene” perylenetetracarboxylic anhydride and “green gene” molecular sensors, successfully constructing a dual-excitation, dual-emission ratiometric fluorescent probe (PBN-1) with favorable biosafety properties, excellent photostability and promising sensitivity. PBN-1 sustainability dynamically tracked ClO-/GSH oxidation fluctuations in HepG2 cells and zebrafish. Notably, PBN-1 distinguished dramatically the fluctuations of ClO-/GSH in zebrafish at different growth and developmental periods. We expect that PBN-1 could provide an effective method for the design of future ratiometric fluorescent probes and expand the application of polysiloxanes in bioimaging.

Thiol-acrylate side-chain liquid crystal elastomers.

The Michael addition ‘click’ chemistry was used to graft acrylate-terminated mesogenic groups onto the polysiloxane backbone polymer chain with thiol functional groups, with a constant 15% fraction of diacrylate reacting monomers as crosslinkers. Three different types of mesogens were used, and also their 50 : 50 mixtures, and in all cases we have obtained the smectic-A phase of the resulting liquid crystalline elastomer. Using X-ray diffraction, calorimetry and dynamic mechanical analysis, we investigated the relationship between the molecular structure of mesogenic side groups and the structure and properties of the elastomers. The shape-memory of smectic elastomers was verified. The unusual features were the semi-crystalline nature of elastomers with non-polar mesogens and the clear role of side-by-side rod dimerization of polar mesogens leading to a higher smectic layer spacing. We investigated the evolution of the smectic alignment on uniaxial stretching along the layer normal and identified two distinct ways in which the elastomer responds: the coarsened Helfrich–Hurault zig-zag layer texture and the large-scale stripe domains of uniform layer rotation in the systems with lower order parameter and the associated layer constraints.

Mechanically Strong, Autonomous Self‐Healing, and Fully Recyclable Silicone Coordination Elastomers with Unique Photoluminescent Properties

The combination of excellent mechanical performances, high reprocess efficiency, and wide-range tunability for functional dynamic siloxane materials is a challenging subject. Herein, the fabrication of mechanically strong, autonomous self-healing, and fully recyclable silicone elastomers with unique photoluminescent properties by coordination of poly(dimethylsiloxane) (PDMS) containing coordination bonding motifs with Zn2+ ions is reported. Salicylaldimine groups, which are introduced into the polysiloxane backbone via mild Schiff-base reaction, coordinate with zinc ions to form elastomeric networks The obtained supramolecular elastomers have excellent mechanical properties, with the optimized tensile strength up to 10.0MPa, which is unprecedented among the reported thermoplastic polysiloxane-based elastomers. Both mechanical properties and stress relaxation kinetics are tunable via adjusting the length of PDMS segments or the molar ratio of metal versus salicylaldimine. Furthermore, these elastomers can be conveniently healed and recycled to regain their original mechanical properties and integrity under mild conditions. In addition, this new kind of polysiloxane also exhibits coordination-enhanced fluorescence, showing great promise for preparing photoluminescent elastomers or coatings.

Photoalignment in Polysiloxane Liquid‐Crystalline Elastomers with Rearrangeable Networks

AbstractMolecular alignment in liquid‐crystalline elastomers with polysiloxane backbone is controlled with the aid of photoalignment and exchangeable links to enhance performance as photoactuators. The photoalignment is triggered by trans‐cis‐trans isomerization of azobenzene moieties, which are introduced at crosslinking points, upon irradiation with linearly polarized UV (LPUV) light under heating. The induced alignment is memorized by rearrangement of network structures through exchange reactions of covalent bonds. When irradiated with LPUV light, freestanding films show bending along with the alignment change in surface regions. Macroscopic shapes are also rememorized by exchange reactions at crosslinks. Combination of photoalignment and network rearrangement allows continuous deformation of freestanding films upon exposure to LPUV light with varying polarization directions. This approach enhances the degree of freedom in alignment control, photoactuation, and reshaping of polysiloxane‐based liquid‐crystalline elastomers, which are feasible as soft actuators.

Synthesis and properties of thermoplastic and dissolvable polysiloxanes containing polyhedral oligomeric silsesquioxane

AbstractThere are many benefits associated with thermoplastic silicones, but very few examples exist: silicone resins or rubbers are normally thermosets. In this article, a facile and efficient approach was reported to prepare thermoplastic silicone by introducing a bulky side siloxane group. Monofunctional polyhedral oligomeric silsesquioxane (POSS), as the bulky siloxane group, was grafted onto the linear polysiloxane backbone via thiol–ene click reaction, endowing the liquid polysiloxane with thermoplastic nature. The POSS‐grafted polysiloxane could be remolded by a hot‐melting or solution casting process. It was worth noting that the novel thermoplastic silicone was composed of both linear siloxane main chains and siloxane side groups, which was distinctly different from previous researches on thermoplastic silicones consisted of siloxane main chains and organic side groups. Thermal analysis, rheological characterization and molecular dynamics simulation results revealed the thermoplastic properties of POSS‐grafted polysiloxane depended on the bulky POSS's hindrance to the movement of the polymer backbone rather than the interaction between the organic side groups.

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

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

Structure of vinyl polysiloxane on properties of polyacrylates film and its pigment printing application

Polysiloxane is a promising modified material due to its good hydrophobicity and toughness, but it suffers from serious uneven distribution and migration during film formation process which gradually lead to the destruction of the hydrophobic structure. A novel silicon-modified copolymer with different molecular weight and vinyl content was synthesized to overcome this problem: an appropriate amount of double bonds between the polysiloxane backbone ensures uniform distribution. Moreover, a multicrosslinked network binder was prepared by miniemulsion polymerization of the polyacrylate copolymers and polysiloxane. Unlike the common crosslinked network of an uneven distribution and migration of silicone backbone, the polysiloxane with suitable crosslinking degree and molecular weight could be effectively distributed evenly during the film formation process. As a result, a better hydrophobicity and toughness performance (89.7° ± 0.5°, 2500% elongation at break) was achieved with this novel poly(methylvinylsiloxane) with 11,024 g/mol at 0.804 mmol/g vinyl content. The product was applied to pigment printing with better wet rubbing fastness and soft handle compared with the unmodified polyacrylates binder. The DSC, SAXS, and XPS indicated that high molecular organosilicon chain and moderate vinyl content were prone to phase separation and obviously shifted onto the surface of film, enriching a uniform organosilicon layer, which played a vital role in the surface hydrophobicity and mechanical properties.

Porous films from cyclic block copolymers

Porous films are attractive materials used in numerous fields, such as catalysis, templating, and separation. In previous examples of porous films prepared from block polymers, the pore size was usually determined by various factors, including mutual interaction between polymer chains, and was hard to precisely manipulate by modification of the block polymers. Herein, we report a novel method of preparing porous films from cyclic block copolymers with the pore size determined by the size of individual components. The incompatibility of the dangling polystyrene arms and cyclic polysiloxane backbones drove the assembly, which then led to the vertical alignment of the cyclic polysiloxane backbone to form porous films. Coarse-grained molecular dynamics simulations were also implemented to gain insight into the assembly process and the film microstructure at the molecular scale. A cyclic block copolymer allows feasible fabrication of porous films through designed interaction between its macromolecular arms. The morphology of pores is directly determined by the structural features of the block copolymer and can be easily tuned by modification of the length of its ring and arms.

Synthesis and properties of a novel asymmetric gemini surfactant based on siloxane skeleton

The paper introduced a kind of hydrogen-containing epoxy polysiloxane skeleton of different chain lengths with a defined molecular weight. Based on the skeleton, a novel asymmetric gemini siloxane surfactant (AGSS) was synthesized by reacting with maleic anhydride monoester and taurine. The chemical structure of AGSS was characterized by 1H NMR and FT-IR. At the same time, the physical and chemical properties of the three oil displacants were systematically studied. The results show that the minimum surface tension of the series of oil displacing agents is 29.02 mN/m, and the corresponding critical micelle concentration (cmc) is 0.416 mmol/L. As the silica chain in the polysiloxane backbone increases from n = 0 to n = 8, the surface tension corresponding to the critical micelle concentration decreases, much lower than conventional hydrocarbon surfactants. Besides, the study results show that the AGSS have good temperature resistance, salt resistance and resistance to divalent ions (Ca2+, Mg2+), and the above properties meet the needs of oil displacement applications.

Polysiloxanes Modified by Thiol‐Ene Reaction and Their Interaction with Gold Nanoparticles

AbstractA poly(vinylmethyl‐co‐dimethyl)siloxane has been functionalized with phenylethanethiol, N‐methylmercaptoacetamide and heptadecafluoro‐1‐decanethiol by a thermal radical thiol‐ene reaction initiated by azobisisobutyronitrile. The resulting polymers were obtained in good yields with most of the time a complete conversion of the vinyl groups. The reaction also preserved the fragile polysiloxane backbone. The polymer, grafted with about 25 % of mercapto‐acetamide groups is soluble in polar solvents such as dimethylformamide and dimethyl sulfoxide, opening the way for further functionalization with polar molecules such as unprotected carbohydrates. Spherical and branched gold nanoparticles were coated with these polymers. This coating induced a surface resonance plasmon shift resulting from the interaction of the grafted polysiloxanes with the nanoparticle surface. The shift can be explained by the variation of the refractive index of the side groups but may be also related to the self‐organization of polysiloxanes and their interactions with the gold surface depending on their polarity.

High-performance solid polymer electrolytes for lithium ion batteries based on sulfobetaine zwitterion and poly (ethylene oxide) modified polysiloxane

Herein we report a new high ionic conductivity and wide electrochemical window solid polymer electrolyte (SPE), which is developed via grafting sulfobetaine zwitterion (ZI) and poly (ethylene oxide) (PEO) chains on highly flexible polysiloxane backbone followed by crosslinking of tri(ethylene glycol) divinyl ether. The synergistic effect of zwitterion and PEO endows the SPE with an excellent ionic conductivity of 3.39 × 10−4 S cm−1 and the wide electrochemical stable window of 5.0 V (vs. Li/Li+) at room temperature. LiFePO4/Li half-cells with as-prepared solid polymer electrolyte present a high initial discharge capacity of 155 mAh g−1 and superior cycle stability with a capacity retention of 93% at 0.1 C after 100 cycles at 30 °C. In addition, LiNi0.5Mn1.5O4/Li half-cells employing such polymer electrolyte also deliver excellent cycle performance and stability. The above results indicate that the designed zwitterionic SPE appears to be a potential candidate for application in all-solid-state lithium-ion batteries.

Grafting triphenylamine groups onto polysiloxanes to improve interaction between the electrochromic films and ITO

A novel series of triphenylamine (TPA)-contained polysiloxanes (PTPASi) have been synthesized by a normal reaction of hydrosilylation through poly(methylhydrosiloxane)(PMHS) with four TPA-based alkenes (TPAA) for electrochromic applications. Grafting TPA onto polysiloxanes was employed as a strategy to ameliorate the thermal stability and cycle stability of the electrochromic properties due to the enhanced force of adhesion between the polymer films and the ITO substrate. The morphology and impedance of the polymers after electro-oxidizing reaction was studied and didn’t reveal significant change suggesting good stability of the hybrid system. Meanwhile, with the introducing of the polysiloxane backbones, the four polymer films appeared nearly colorless in their natural state, in contrast to three primary colors of red, green and blue in their oxidized state. Hence, these PMHS films can be mixed to obtain all the other colors on the basis of the color mixing theory. In addition, the potential switching properties of the four polymers at the temperature of 150°C have been investigated for the first time, which indicate high thermal stability and potential for relatively high temperature and/or long term cycling applications.

ポリ（シルアリーレンシロキサン）誘導体を用いたシリコーンゴム創製

Polydimethylsiloxane (PDMS) is the typical material for catheter, although the excellent biocompatibility of PDMS, PDMS has some problems such as difficulty in coating and operability. We consider the introduction of an aromatic ring with sulfobetaine substituents into the main chain of PDMS to solve the problems. Poly(tetramethylsilphenylenesiloxane)(PTMS) is the representative polymer where an aromatic moiety is incorporated into the polysiloxane backbone, which would presumably improve the good properties of polysiloxane, especially the thermostability. It has been reported that the properties of poly(tetramethylsilarylenesiloxane) derivatives depend on the kind of arylene moiety, the substituted position of dimethylsilyl groups as well as the substituent, on the arylene moiety. Therefore, we examined the synthesis and physical properties of the multi-block copolymer based on polysiloxane with sulfobetaine substituents.

The influence of the aromatic character in the gas chromatography elution order: the case of polycyclic aromatic hydrocarbons

ABSTRACTA link between the aromatic character of polycyclic aromatic hydrocarbons (PAHs) and gas chromatography (GC) elution order in columns with a polysiloxane backbone in the stationary phase is reported for the first time. The aromatic character was calculated using a method that combines the π-Sextet Rule and the Pauling Ring Bond Orders to allow the establishment of the location and migration of aromatic sextets in PAH structures. One GC column with a polysiloxane-like backbone (Rxi-PAH) and three GC columns with a polysiloxane backbone (DB-5, SE-52 and LC-50) were used for the analysis. According to the results of this study, within an isomer group, PAHs that contain a lower number of rings affected by the aromatic sextets tend to elute earlier than PAHs that contain a higher number of rings affected by the aromatic sextets. The PAHs that follow the calculated elution order are 88% in the Rxi-PAH column, 88% in the DB-5 column, 93% in the SE-52 column and 85% in the LC-50 column. It is expected that future analyses with other aromatic compounds in GC columns with a polysiloxane backbone in the stationary phase will follow a GC elution order that agrees with the aromatic character of the molecules.

Photomobile Liquid-Crystalline Elastomers with Rearrangeable Networks.

Incorporation of dynamic covalent bonds into photomobile liquid-crystalline elastomers with a polysiloxane backbone enables the alignment of mesogens and macroscopic shapes to be controlled through the rearrangement of the network topology, even after the formation of chemically crosslinked networks. The reshaped samples show various sophisticated 3D motions upon irradiation with UV and visible light, depending on their initial shapes.

Temperature and humidity effect on aging of silicone rubbers as sealing materials for proton exchange membrane fuel cell applications

Durability and reliability of seals around perimeter of each unit are critical to the lifetime of proton exchange membrane fuel cells. In this study, we investigate the aging of silicone rubbers with different hardness, often used as sealing materials for fuel cells, subjected to dry and humidified air at different temperatures. The aging properties are characterized by variation of permanent compression set value under compression, mechanical properties, and surface morphology as well. The results show that aging of silicone rubbers becomes more severe with the increase in subjected temperature. At temperature above 100°C, silicone rubbers are not suitable for fuel cell applications. The existed water molecules from humidified gases can accelerate the aging of silicone rubbers. Among the tested samples, silicone rubber with hardness of 40 is more durable than that with hardness of 30 and 50 for fuel cells. The change of chemical structure after aging suggests that the aging of silicone rubbers mainly results from the chemical decomposition of cross-linker units for connection of polysiloxane backbones and of methyl groups attached to silicon atoms.