Methyl Silsesquioxane Research Articles

Rational synthesis of methylsilsesquioxane aerogels addressing thermal load and compression recovery issues in Li-ion batteries

Li-ion batteries suffer from two key safety issues: thermal overload and compression recovery, which may lead to flammability and mechanical failure. Silica aerogels are promising solutions to both these issues owing to their excellent thermal stability and tailored mechanical properties. However, finding the optimum sol composition in sol-gel-based aerogel synthesis is needed to address these issues at industry-relevant scales. Here, we propose an innovative approach to determine the optimum sol composition for methylsilsesquioxane (MSQ) aerogel sheets, which is based on the mechanisms of the effects of molar ratios of hydrolysis water and isopropyl alcohol (IPA) to methyltrimethoxysilane (MTMS) on the physical properties of MSQ aerogel sheets and according to the ternary contour distribution of their properties. The synthesized MSQ aerogels exhibited a soft, light, and powderless texture and featured superhydrophobic properties (150.2°), low thermal conductivity of 33.6 mW/(m·K), high thermal stability temperature in nitrogen atmosphere at 479.3 °C and moderate short-term (<6 h) service temperature of 120.0 °C. Significantly, the structural stability and elasticity of the aerogels surpassed the current state-of-the-art, showing recovery to 81.3 % of the original thickness and 85.2 % of the original stress after being subjected to 400 cycles of high-speed and high-strain consecutive compression, respectively. These excellent properties make the MSQ aerogel sheets promising for applications in thermal load and compression recovery management of diverse energy storage devices, including batteries for next-generation electric vehicles

Fast Solution Blow Spinning of Lotus-Leaf-Inspired SiO2 Nanofiber Sponge for High Efficiency Purification.

Massive production of SiO2 nanofibers with both high durability and exceptional performance remains a significant challenge. Herein, a novel approach was introduced to achieve the massive production of SiO2 nanofibers with lotus-leaf-inspired surfaces by combining solution blowing spinning (SBS) and the polymer-derived ceramics method. Based on the SBS technique, three types of precursor nanofiber products were fast spined with methyl silsesquioxane polymer and polymethyl hydrogen siloxane employed as Si sources. The flow rate of the SBS spined Si-based ceramic nanofibers was enhanced to 20 mL·h-1. Furthermore, through the integration of hydrophobic-oleophilic SiO2 nanoparticles into the precursor solution, SiO2 nanofibers with lotus-leaf nanoprotrusion surfaces were fabricated. Nanoparticle-decorated SiO2 fibers demonstrated excellent hydrophobicity (138.3°), compression resilience (∼60%), proficiency in organic pollutant adsorption, high-temperature resistance (∼1100 °C), and outstanding thermal insulation properties (thermal conductivity of 0.0165 W·(m·K)-1).

Organic-Inorganic Hybrid Synaptic Transistors: Methyl-Silsesquioxanes-Based Electric Double Layer for Enhanced Synaptic Functionality and CMOS Compatibility.

Electrical double-layer (EDL) synaptic transistors based on organic materials exhibit low thermal and chemical stability and are thus incompatible with complementary metal oxide semiconductor (CMOS) processes involving high-temperature operations. This paper proposes organic-inorganic hybrid synaptic transistors using methyl silsesquioxane (MSQ) as the electrolyte. MSQ, derived from the combination of inorganic silsesquioxanes and the organic methyl (-CH3) group, exhibits exceptional thermal and chemical stability, thus ensuring compatibility with CMOS processes. We fabricated Al/MSQ electrolyte/Pt capacitors, exhibiting a substantial capacitance of 1.89 µF/cm2 at 10 Hz. MSQ-based EDL synaptic transistors demonstrated various synaptic behaviors, such as excitatory post-synaptic current, paired-pulse facilitation, signal pass filtering, and spike-number-dependent plasticity. Additionally, we validated synaptic functions such as information storage and synapse weight adjustment, simulating brain synaptic operations through potentiation and depression. Notably, these synaptic operations demonstrated stability over five continuous operation cycles. Lastly, we trained a multi-layer artificial deep neural network (DNN) using a handwritten Modified National Institute of Standards and Technology image dataset. The DNN achieved an impressive recognition rate of 92.28%. The prepared MSQ-based EDL synaptic transistors, with excellent thermal/chemical stability, synaptic functionality, and compatibility with CMOS processes, harbor tremendous potential as materials for next-generation artificial synapse components.

Functional characterization of nano-porous silicate-polymer composite for bovine serum albumin immobilization

The paper dwells upon the elaboration of a simple and energy-efficient approach for the “bottom-up” fabrication of porous polymeric film, which possesses unique surface, structural and bulk properties, followed by its comprehensive study through various characterization techniques. The fabricated film is multi-layered methyl silsesquioxane and suitably modified with the help of several treatments making the film compatible for biosensing applications. Film characterization reports the self- organized topography of the film deposited over the substrate and confirms the successful bonding between the polymers. The influence of the concentration of polypropylene glycol, which itself acts as thermally labile dendrimer, is studied by observing its bond formation ensuring polymer mixing by using FTIR. Energy dispersive x-ray analysis has been performed for the confirmation of elements. In addition to this, the nanoporous film is also studied with the help of variable angle spectroscopic ellipsometry for the determination of film porosity and refractive index. In this analysis, Cauchy model and graded-index model were chosen for data analysis and the Bruggeman effective medium approximation method was used for evaluating the optical constant. The surface of the porous film has been treated with different silane surfaces, characterized with the help of FTIR, UV-VIS, and AFM and envisioned for protein immobilization.

Silsesquioxanes-Based Nanolubricant Additives with High Thermal Stability, Superhydrophobicity, and Self-cleaning Properties

Nanoadditives are promising materials for long-envisioned next-generation lubricants to achieve excellent tribological performance and thermal stability. Here, an instigative and novel approach has been scrutinized to facilely prepare the nanolubricant additive. For this purpose, three synthetic strategies were designed for i) preparation of uniform-sized poly(methyl silsesquioxane) (PMSQ) nanoparticles, ii) hydrosilylation of the long carbon chain of ethyl 10-undecenoate and iii) modification of PMSQ nanoparticles with hydrosilylation product through a condensation reaction, in order to obtain long-carbon-chain grafted nanohybrids. The morphology, composition, and properties of these nanohybrids were confirmed by 1H-NMR, FTIR, SEM, EDS, and TGA. The effects of different concentrations of unmodified and modified PMSQ nanoparticles on the tribological properties of silicone oil were discussed. In the comparison of unmodified PMSQ nanoparticles, the modified one performs very well to reduce the coefficient of friction and wear scar diameter at low concentration. The TGA results revealed the extraordinary thermal stability of these particles, as their weight loss was only 19% at 800 °C which is remarkably higher than other solid lubricant additives. In this research, we tried to fill the deficiency of thermally stable material in the field of heavy machinery and industry. In addition, the environment-friendly (fluorine-free), superhydrophobic and self-cleaning surface effect of modified PMSQ nanoparticles was also observed. These silsesquioxane-based nanohybrids having synergistic effects, advantageous scientific values, and promising application prospects are expected to be more useful with other longer carbon chains.

Radiation shielding properties of silicon polymers

We have studied the X-ray and gamma radiation shielding parameters such as mass attenuation coefficient, linear attenuation coefficient, Half Value Layer (HVL), Tenth Value Layer (TVL), effective atomic number, electron density and specific gamma ray constant in some silicon polymers of different composition such as Polymer A- Poly dimethyl siloxane (C2H6OSi), Polymer B- Polymethyl Hydro silaxane (CH4SiO), Polymer C- Per hydro poly silaxane (H3SiN), Polymer D-poly dimethyl silaxane (C2H6Si), Polymer E− Methylsilses quioxane (C12H32O8Si8), and Polymer F- Silalkalyene polymer (SiC3H8). We have also measured the mass attenuation coefficient at gamma energies 84 keV to 1.3 MeV. We have also studied the neutron shielding properties such as coherent neutron scattering length, incoherent neutron scattering lengths, coherent neutron scattering cross section, incoherent neutron scattering cross sections, total neutron scattering cross section and neutron absorption cross sections in the silicon polymers. We have compared the shielding properties among the studied different silicon polymers. From the detail study, it is clear that the silicon polymer per hydro poly silaxane is good absorber for X-ray, gamma radiation and neutron. Hence, we suggest that the perhydropoly silaxane is good shielding material for X-ray, gamma and neutrons.

SiOC-based polymer derived-ceramic porous anodes for microbial fuel cells

The applicability of a new class of ceramic materials in Microbial Fuel Cells (MFCs) was investigated, targeting the development of cost-effective anode materials with long-term durability. In this work, silicon oxycarbide (SiOC)-based porous anodes were prepared by the polymer-derived ceramics (PDCs) route, using poly(methyl silsesquioxane) and poly(methyl phenyl silsesquioxane) as precursors while incorporating carbonaceous fillers (graphite and carbon black) and metal precursor (NiCl2). Tape casting was used in the manufacturing followed by pyrolysis at 1000 °C under nitrogen atmosphere. The interior structure and surface morphology were characterized with scanning electron microscopy (SEM), nitrogen adsorption, vapor adsorption, and contact angle measurements. The developed anodes were tested in MFC with aqueous cathode configuration using a low-cost clayware cylinder as the anodic chamber. The performance of MFC using PDC-based anodes was compared with MFC having carbon felt as anode material, which showed a two-fold increase in power density (211 and 111 mW m−2, respectively) and normalized energy recovery in former and also demonstrated chemical oxygen demand (COD) removal efficiency of about 85%. The improved performance of the PDC-based anodes is attributed to its porous structure, hydrophilic surface, and high specific surface area (39.89 m² g−1). The biocompatibility was confirmed by biofilm growth on the surfaces, while a sufficient electrical conductivity (0.10–0.18 S cm−1) makes it superior electrode material for application in MFCs.

Fabrication and Characterization of MSQ Aerogel Coating on ePTFE Thin Films for Cable Sheaths.

With methylsilsesquioxane (MSQ) aerogels synthesized by the sol-gel method as a raw material and Si-Ti sol as a binder, an alcohol-based aerogel slurry consisting of only MSQ aerogel and Si-Ti sol was prepared and coated on expanded polytetrafluoroethylene (ePTFE) to form an MSQ aerogel coating layer, followed by low-temperature heat treatment. The effect of Si-Ti sol content on the microstructure of the MSQ aerogel coating layer was investigated, and the properties of a typical MSQ aerogel-layer-coated ePTFE film were evaluated. The results show that Si-Ti sol has an important role in terms of film-forming capability, surface smoothness, flexibility, and powder dropping of the MSQ aerogel coating layer. With a Si-Ti sol of 10.5 wt.% content as a binder and after heat treatment at 170 °C for 30 min, the coated ePTFE flexible thin film with a layer thickness of 30 μm shows high uniformity, integrity, and electrical insulation properties, with an elongation at break decrease over 130%, a thermal conductivity of 0.1753 W/(m·K) at 25 °C, a dielectric constant of 16.5674, and a dielectric loss of 0.06369, which can be promisingly applied in cable sheaths.

Facile Synthesis of Methylsilsesquioxane Aerogels with Uniform Mesopores by Microwave Drying.

Methylsilsesquioxane (MSQ) aerogels with uniform mesopores were facilely prepared via a sol–gel process followed by microwave drying with methyltrimethoxysilane (MTMS) as a precursor, hydrochloric acid (HCl) as a catalyst, water and methanol as solvents, hexadecyltrimethylammonium chloride (CTAC) as a surfactant and template, and propylene oxide (PO) as a gelation agent. The microstructure, chemical composition, and pore structures of the resultant MSQ aerogels were investigated in detail to achieve controllable preparation of MSQ aerogels, and the thermal stability of MSQ aerogels was also analyzed. The gelation agent, catalyst, solvent, and microwave power have important roles related to the pore structures of MSQ aerogels. Meanwhile, the microwave drying method was found to not only have a remarkable effect on improving production efficiency, but also to be conducive to avoiding the collapse of pore structure (especially micropores) during drying. The resulting MSQ aerogel microwave-dried at 500 W possessed a specific surface area up to 821 m2/g and a mesopore size of 20 nm, and displayed good thermal stability.

Ultralight, hydrophobic, monolithic konjac glucomannan-silica composite aerogel with thermal insulation and mechanical properties

Konjac glucomannan (KGM) aerogel was prepared by a facile freeze-drying process, which was used as green sustainable biopolymer matrix to synthesis three-dimensional (3D) network interpenetrated KGM-SiO2 aerogel with thermal insulation performance and high mechanical properties. Herein, we explored that the potential structure–performance relationship of KGM aerogel between the physical parameters, morphology and thermal insulation. Besides, the preparation conditions of KGM aerogel including concentration of KGM, Na2CO3-to-KGM mass ratio were investigated. Meanwhile, the KGM aerogel and KGM-SiO2 aerogel were characterized using scanning electron microscopy, Fourier transform infrared spectrometer, Brunauer-Emmett-Teller method, thermogravimetric analysis and contact angle test. Results showed that the as-prepared KGM aerogel exhibited excellent thermal insulation performance (λ = 0.021 W m−1 K−1) and low bulk density (ρ = 0.030 g cm−3) when concentration of KGM was 2 wt% and Na2CO3-to-KGM mass ratio of 0.12. In order to improve the mechanical properties and high hydrophobicity of biopolymer aerogel, a novel of KGM-SiO2 aerogel was successful fabricated by incorporating methylsilsesquioxane (MTES) derived SiO2 into the KGM matrix via the freeze-drying method. The obtained aerogel exhibited remarkable compressive strength (δmax = 1.65 MPa at 80% strain), high specific surface area of 416.1 m2 g−1, high hydrophobicity (θ = 146° for water) and low thermal conductivity of 0.032-0.039 W m−1 K−1. Thus, the high-performance KGM-SiO2 aerogel would be further expand the thermal insulation application in sustainable development and energy-saving building.

Structure and its thickness dependence of thin films of phenyl and methyl silsesquioxane polymers

Silsesquioxane (SSQ) polymers are important thin film materials in lithography, sensing, opto materials, and low k materials in electronics applications. There is a strong fundamental and practical need to understand the network structure in silsesquioxane films. In this study, two types of SSQ polymer (PSSQ), poly(methylsilsesquixoane) (PMSSQ) and poly(phenylsilsesquioxane) (PPhSSQ), were synthesized and their thin films were examined. Grazing angle reflection absorption infrared spectroscopy (GARAIR) was shown to be a good method to characterize the structure of the SSQ films and quantitative analysis can be done on films of a range of thickness between 7 nm and 150 nm. In particular, the orientation of the Si-O-Si network can be probed with GARAIR due to the polarization effect of the measurement. With increasing film thickness, a decrease in the planarity of the chains (orientation) in the Si-O-Si network was observed and possibly an increasing in the degree of condensation happened as indicated by the red shift of one IR absorption peak in PMSSQ. XRD study shows that both PMSSQ and PPhSSQ films have similar network comprising ladder component. Furthermore, GARAIR established that PPhSSQ shows more isolated silanol content while PMSSQ possesses mostly vicinal silanols.

Facile Synthesis of Flexible Methylsilsesquioxane Aerogels with Surface Modifications for Sound- Absorbance, Fast Dye Adsorption and Oil/Water Separation.

New flexible methylsilsesquioxane (MSQ) aerogels have been facilely prepared by a sol–gel process with methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) as co-precursors, followed by surface modification and ambient pressure drying. The microstructure, mechanical properties and hydrophobicity of these MSQ aerogels after surface modifications of hexamethyldisiloxane (HMDSO) and/or hexamethyldisilazane (HMDS) were investigated in detail, and the applications of surface-modified MSQ aerogels in sound-absorbance, fast dye adsorption and oil/water separation were evaluated, respectively. The MSQ aerogels surface-modified by HMDS possess flexibility, elasticity and superhydrophobicity, and demonstrate good performance in the mentioned applications. The resultant MSQ aerogel used in sound-absorbance has high frequency (about 6 kHz) acoustic absorptivity of up to 80%, benefiting from its macroporous structure and porosity of 94%, and it also possesses intermediate frequency acoustic absorptivity (about 1 kHz) up to 80% owing to its elasticity. This MSQ aerogel can selectively separate oil from oil/water mixtures with high efficiency due to its superhydrophobicity and superlipophilicity, resulting from a lot of methyl groups, density as low as 0.12 cm3·g−1 and a water contact angle as high as 157°. This MSQ aerogel can be assembled to be a monolithic column applied for fast dye adsorption, and shows selective adsorption for anionic dyes and removal efficiency of methyl orange of up to 95%.

Fabrication of highly monodisperse CeO2@poly(methyl silsesquioxane) microspheres and their application in UV‐shielding films

ABSTRACTHighly monodisperse CeO2@poly(methyl silsesquioxane) (PMSQ) microspheres were successfully prepared by a facile chemical precipitation technique. The structures and properties of CeO2@PMSQ were analyzed by Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy techniques. We confirmed that the PMSQ microspheres were uniformly coated by CeO2 nanoparticles, with about an 8 nm crystallite diameter. Then, CeO2@PMSQ was incorporated into a poly(vinyl alcohol) (PVA) matrix to fabricate PVA/CeO2@PMSQ composite films by the casting of homogeneous solutions. The thermal and optical properties of the composite films were investigated by thermogravimetric analysis and UV–visible spectroscopy. The results show the high UV‐shielding efficiency of the composites: for a film containing 2.5 wt % CeO2@PMSQ microspheres, about 80% UV light at wavelengths between 200 and 360 nm was absorbed, whereas the optical transparency in the visible region still remained very high. The addition of CeO2@PMSQ microspheres improved the thermal stability of the PVA films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45065.

Operating mechanisms of highly-reproducible write-once-read-many-times memory devices based on graphene quantum dot:poly(methyl silsesquioxane) nanocomposites

Resistive switching memory devices were fabricated utilizing graphene quantum dot (GQD):poly(methyl silsesquioxane) (PMSSQ) hybrid nanocomposites. Current-voltage curves for the Al/GQD:PMSSQ/indium-tin-oxide devices at room temperature showed write-once-read-many-times memory (WORM) characteristics with an ON/OFF ratio of as large as 106 due to the homogeneous dispersion of the GQDs in the PMSSQ matrix. The WORM devices maintained retention times larger than 2 × 104 s under ambient conditions. The devices showed high device-to-device reproducibility with threshold-voltage distributions between 3 and 5 V. The ON state currents remained between 10−6 and 10−3 A, and the OFF state currents maintained between 10−12 and 10−9 A. The operating mechanisms concerning the interaction between the GQDs and the PMSSQ matrix for the resistive-switch phenomenon were analyzed on the basis of the I–V results and with the aid of the energy band diagram.

Millimeter-Wave GaN HEMTs With Cavity-Gate Structure Using MSQ-Based Inter-Layer Dielectric

We have fabricated millimeter-wave gallium nitride high electron mobility transistors (GaN HEMTs) using methyl silsesquioxane (MSQ)-based inter-layer dielectric to suppress current collapse by enhancing the moisture resistance, and removed MSQ around the gate electrode for reducing parasitic capacitance. We clarified that the moisture resistance of conventional benzocyclobutene (BCB) is insufficient to suppress current collapse because water molecules easily permeate BCB, especially when using a cavity-gate structure. On the other hand, the moisture resistance of MSQ is very high because of the excellent hydrophobic property, and the current collapse due to moisture was effectively suppressed. So, improving the moisture resistance with hydrophobic low-k films plays a key role in reducing the current collapse of GaN HEMTs, especially when using a cavity-gate structure. Moreover, the parasitic capacitance of GaN HEMTs was successfully reduced by using the MSQ-cavity, and RF performance was improved by around 20%.

Hysteresis free carbon nanotube thin film transistors comprising hydrophobic dielectrics

We present two examples of carbon nanotube network thin film transistors with strongly hydrophobic dielectrics comprising either Teflon-AF or a poly(vinylphenol)/poly(methyl silsesquioxane) (PVP/pMSSQ) blend. In the absence of encapsulation, bottom gated transistors in air ambient show no hysteresis between forward and reverse gate sweep direction. Device threshold gate voltage and On-current present excellent time dependent stability even under dielectric stress. Furthermore, threshold gate voltage for hole conduction is negative upon device encapsulation with PVP/pMSSQ enabling much improved current On/Off ratio at 0 V. This work addresses two major challenges impeding solution based fabrication of relevant thin film transistors with printable single-walled carbon nanotube channels.

Interaction of SF6 and O2 plasma with porous poly phenyl methyl silsesquioxane low-κ films

A reduction in the κ-value of dielectric materials is of great interest today as it leads to the reduction of resistance–capacitance delays and parasitic capacitances within integrated circuits, thereby improving device performance. We have recently reported our studies on the great potential of the Poly phenyl methyl silsesquioxane (PMSQ) low-κ films (κ = 2.7 ± 0.2) for interlayer dielectric applications. Here we report on the deposition and characterisation of porous PMSQ thin films using Heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin as the porogen. A reduction in the κ-value of the films was achieved as a function of the increase in porogen loading in the film. The removal of the thermally liable porogen material from the hybrid films was studied using thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The change in density as a function of the porosity was studied using x-ray reflectivity techniques. The interaction of the films with pure SF6 and O2 plasmas was studied and the surface modification that occurs in the films as a result of the interaction was studied using FTIR and x-ray photoelectron spectroscopy. A change in the κ-value of the films was observed after plasma treatment which is attributed to the chemical modification of the film surface due to plasma interaction.

Low damage etching method of low-k material with a neutral beam for interlayer dielectric of semiconductor device

To reduce the cross-talk between nanoscale devices, low-k materials such as methyl silsesquioxane (MSQ), which is damaged easily during plasma etching, are introduced as an intermetallic dielectric material in addition to the use of copper as the conducting material for the reduction of parasitic resistance and capacitance. In this study, beam techniques such as neutral/ion beams were used in the etching of MSQ and the effect of these beam techniques on the reduction of the degradation of the MSQ were investigated. When MSQ was etched using the same CF4 etch gas at the similar etch rate as that used for conventional MSQ etching using inductively coupled plasmas (ICPs), the neutral/ion beam etching showed lower F contents and lower penetration depth of F, indicating decreased degradation by fluorination of MSQ during etching using the beam techniques. Especially, the neutral beam etching technique showed the lowest F contamination and the lower penetration depth of F among the etch methods. When the dielectric constant was measured after the etching of the same depth, the MSQ etched with the neutral beam showed the lowest change of the dielectric constant, while that etched using the ICP showed the highest change of dielectric constant. The lower degradation, that is, the lower chemical modification of MSQ material with the beam technique is believed to be related to the decreased concentration of radical species in the processing chamber reacting with the MSQ surface, while the lowest degradation using the neutral beam is believed to be due to the lower reaction rate of the reactive neutral compared to reactive ions.

Robust spin-on-glass poly(methyl)silsesquioxane-based low-k materials derived from a cyclic siloxane precursor

Low dielectric constant poly(methyl)silsesquioxane spin-on-glass resins incorporating a cyclic precursor exhibited exceptional mechanical properties to withstand CMP processes.

Reduction in current collapse of AlGaN/GaN HEMTs using methyl silsesquioxane‐based low‐k insulator films

We have investigated the effect of moisture on current collapse of AlGaN/GaN high‐electron mobility transistors (HEMTs) when using low dielectric constant (low‐k) insulator films to reduce the parasitic capacitance of millimeter‐wave amplifier monolithic microwave integrated circuits. We clarified that current collapse is caused by moisture uptake through the surface and the sidewall of low‐k films. Moreover, the moisture resistance of conventional carbon‐based low‐k films, such as benzocyclobutene, are insufficient to suppress current collapse because of hydrophilic surface and highly hydrophilized sidewall by the contact hole etching. We proposed the use of methyl silsesquioxane (MSQ)‐based low‐k films to improve the moisture resistance because of methyl group's hydrophobic property. This is the first time that MSQ has been used in AlGaN/GaN HEMTs. After appling MSQ, the moisture resistance of low‐k films at the surface and the sidewall improved, and current collapse due to humidification was successfully reduced. Our findings suggest that improving the moisture resistance with hydrophobic low‐k films does play a key role in reducing current collapse of AlGaN/GaN HEMTs.