Polydimethylsiloxane Polymer Research Articles

A grafted-liquid lubrication strategy to enhance membrane permeability in viscous liquid separation

While membrane technology has shown promising separation applications, efficient separation of viscous organic liquids remains a great challenge as they can readily adhere to and foul membranes, leading to severely declined permeation flux and even failure of the membranes. Herein, a unique grafted-liquid lubrication strategy is introduced for the first time by covalently grafting highly flexible polydimethylsiloxane (PDMS) brushes onto membranes to tackle the above challenge. The PDMS polymer brush featuring extremely low glass transition temperature (Tg: 127 °C) is rotationally dynamic at room temperature and acts as a liquid-like lubrication layer, which can both reduce the foulant adhesion and promote liquid slippage at the membrane-liquid interface. As a result, a remarkably improved permeation flux and superior antifouling ability towards highly viscous organic liquids (i.e., crude oil) are achieved for the PDMS-brush lubricated membrane compared with conventional solid membranes of similar surface structure and wettability. It is believed that the grafted-liquid lubrication strategy will open a promising avenue for developing high-performance membranes dealing with viscous liquids.

Facile synthesis of composite films featuring bulk superhydrophobicity, durability, and repairability for aquatic show

Synthesis of bulk superhydrophobic composite materials with durable and repairable properties is of important theoretical and practical significance. Herein, a bulk superhydrophobic composite film (BSCF) is fabricated by integrating organic polymer components, polyurethane acrylate (PUA) and polydimethylsiloxane (PDMS), and inorganic component, silica particles (SiO2). Due to the bulk deposition and construction of the covalently cross-linking polymer scaffolding, the composite film exhibits a unique bulk superhydrophobic property, which is capable of being exposed to the surface under mechanical shear to preserve durable superhydrophobicity. Therefore, the extreme water repellency of the BSCF maintains unaltered even cyclic sandpaper abrasion is conducted (>150 cycles). By exploiting the advantage of the extreme water repellency inside the composite film bulk, the BSCF is also able to repair its deprived superhydrophobicity via a sanding treatment (>30 cycles), which is completely different from the depletion of healing agents. Furthermore, the aquatic light-reflective function of superhydrophobic materials is exploited in this work for the first time and the exploitation of it may broaden the potential application fields of superhydrophobic materials in deep-sea exploitation, undersea transportation, and aquatic decoration. Based on the aquatic light-reflective principle, a series of patterns on the BSCF surface display dazzling light under the illumination of a flashlight and the aquatic show is successfully realized on each layer of the BSCF. Our studies convincingly show a new direction to synthesize composite materials featuring bulk superhydrophobic, durable, and repairable performances for various potential applications.

Experimental study of resistive load for impedance matching of triboelectric energy harvester fabricated with patterned polydimethylsiloxane polymer layer

Impedance matching of the power source with the external load is one of the imperative parameters of any electronic system for the optimized power transfer from the power source to the load. Mismatch in impedance of power source and the external load may cause a drastic reduction in the power transfer due to reflections. In this paper, a systematic experimental study of load matching between energy harvester and load resistance has been presented. The experimental results showed output voltage without external load condition is 68.46 V with the output current of 14.59 µA, consequently instantaneous power of 0.937 mW. Under the optimum load of 4 MΩ, the output power reduced to 0.248 mW. A rigorous experimental study has been carried out under the frequency and force of 4.5 Hz and 2.8 N, respectively. The triboelectric energy harvester device has also been demonstrated for the potential applications of the self-sustained system.

Fabrication of a versatile composite material with three-dimensional superhydrophobic for aquatic show

Versatile composite materials integrating extreme water repellency with a series of characteristics have been seen as potential competitors for innovative applications. In this work, the author designs a three-dimensional superhydrophobic composite material (TSCM) featuring robustness and repairability by utilizing organic polymer components, polydimethylsiloxane (PDMS), and epoxy acrylate (EPA) and inorganic component, silica particle (SiO2). The bulk deposition and construction preparation method enables the TSCM to exhibit a special three-dimensional superhydrophobic property with a contact angle of 161° and a sliding angle of 2°. Benefiting from the establishment of the covalently cross-linking polymer scaffolding, the TSCM is able to withstand multi-cycles mechanical damage (>150 cycles) and present a damage-insensitive performance. Due to the three-dimensional superhydrophobic and roughness-regenerative characteristics, the TSCM also has the capability of repairing its deprived superhydrophobicity by a polishing procedure (>30 cycles), distinguishing the depletion of healing agents. Most importantly, the TSCM is used to exploit the aquatic light-reflective function of superhydrophobic materials for the first time. Desirably, on the basis of the aquatic light-reflective principle, not only the design control is realized but also the aquatic show is accomplished on each layer of the TSCM, which may widen the applications of superhydrophobic materials in various progressive and intelligent fields, such as deep-sea exploitation, undersea transportation, and aquatic decoration. Our studies convincingly show that this is a worthwhile approach to invent versatile composite materials featuring three-dimensional superhydrophobicity, robustness, and repairability for innovative applications.

Enhancing dielectric and piezoelectric properties of micro-ZnO/PDMS composite-based dielectrophoresis

This work aims to enhance the dielectric and piezoelectric properties of polydimethylsiloxane (PDMS) polymer filled with zinc oxide (ZnO) powders. Both ZnO nanoparticles and microparticles are used to prepare piezoelectric composites and a comparison of their dielectric responses is carried out. The experimental results reveal that a higher particle concentration gives rise to the increased dielectric permittivity of composites, especially when particles are aligned in the poling-direction-based dielectrophoretic process. Hence, the microparticles are chosen instead of the nano ones because the microscale facilitates the fabrication process of the composite, especially with high filler content. It also makes it possible to clearly record the movement of particles under alternating (AC) voltage application using optical microscopy. Significant improvement in the dielectric and piezoelectric behavior of the proposed composite has been successfully achieved via dielectrophoretic alignment of ZnO microparticles. This technique leads to increased connectivity between ZnO/ZnO interfaces, allowing for the creation of continuous aligned piezoelectric particles inside the polymer matrix. As a result, the piezoelectric effect is considerably boosted. Finally, the dielectric constant, as well as the charge coefficient of the ZnO particles, is estimated through theoretical approaches for composites containing particles arranged in chains or randomly dispersed. The model predictions are in good agreement with the experimental results. Furthermore, a finite element model (FEM) is developed using Comsol Multiphysics to evaluate these parameters in a 3D structure, which is then compared to those obtained by the above 2D-analytic models.

Mechanical characterization of polydimethylsiloxane (PDMS) exposed to thermal histories up to 300 °C in a vacuum environment

Flexible electronic devices consisting of sensors and interconnects integrated with a soft polymer platform are being considered for emerging applications such as smart clothing, soft robotics, conformal batteries, and biomonitoring decals. Fabrication processes for such devices can require that the polymer platform be subjected to temperatures up to 300 °C without a significant deterioration of its physical properties such as stretchability and stiffness. In this communication, we report the stress–strain behavior of relatively thin sheets of polydimethylsiloxane (PDMS) polymer (thickness ∼30 µm) made with a base-to-hardener ratio of 20:1 and heated up to 300 °C in a vacuum environment. It is shown that in spite of the exposure to high temperatures used in this study, the PDMS sheets maintained their hyperelastic behavior as represented by the Ogden model. The elastic modulus is shown to decrease from 0.81 MPa to 0.62 MPa while average strain to failure is shown to decrease from 250% to 106% as the temperature of thermal exposure in vacuum is increased from 100 °C to 300 °C. The retention of high stretchability even after the thermal exposures opens up the possibility of high-density microelectronic circuit interconnects to be fabricated on PDMS substrates.

Universally autonomous self-healing elastomer with high stretchability

Developing autonomous self-healing materials for applications in harsh conditions is challenging because the reconstruction of interaction in material for self-healing will experience significant resistance and fail. Herein, a universally self-healing and highly stretchable supramolecular elastomer is designed by synergistically incorporating multi-strength H-bonds and disulfide metathesis in polydimethylsiloxane polymers. The resultant elastomer exhibits high stretchability for both unnotched (14000%) and notched (1300%) samples. It achieves fast autonomous self-healing under universal conditions, including at room temperature (10 min for healing), ultralow temperature (−40 °C), underwater (93% healing efficiency), supercooled high-concentrated saltwater (30% NaCl solution at −10 °C, 89% efficiency), and strong acid/alkali environment (pH = 0 or 14, 88% or 84% efficiency). These properties are attributable to synergistic interaction of the dynamic strong and weak H-bonds and stronger disulfide bonds. A self-healing and stretchable conducting device built with the developed elastomer is demonstrated, thereby providing a direction for future e-skin applications.

Non-centrosymmetric zinc silicate-graphene based transparent flexible piezoelectric nanogenerator

Abstract Rapid advancement of transparent flexible electronics has great potential for next-generation energy devices for self-powered nanosystems and nanosensors. Here, we present the transparent and flexible piezoelectric lead free zinc silicate (Zn2SiO4) nanorods-graphene based nanogenerators for harvesting mechanical energies for the first time. A simple and cost effective hydrothermal method was used to synthesize the piezoelectric Zn2SiO4 nanorods with non-centrosymmetricity property. Tetragonal crystal system and dimension of nanorods were investigated using X-ray diffraction spectroscopy and high resolution electron microscopies, respectively. Raman spectra exhibited all characteristic signature peaks of the Zn2SiO4 nanorods. Piezoelectric properties of grown Zn2SiO4 nanorods was confirmed and a piezoelectric charge coefficient (d33) of about 117 p.m./V was obtained through piezoelectric force microscopy study. A high performance piezoelectric hybrid composite nanogenerator was successfully fabricated using polydimethylsiloxane (PDMS) polymer, Zn2SiO4 nanorods and CVD grown monolayer graphene sheet. The average piezoelectric output voltage and current density of 5.5 V and 0.50 μA/cm2 were obtained under very small pressure of 0.15 kgf applied through computer controlled dynamic shaker without applying any external electric poling. The average energy conversion efficiency of the flexible piezoelectric Zn2SiO4: PDMS-based device was found to be ≈ 29.10%. The mechanism of high piezoelectric output performance from Zn2SiO4 nanorods device was discussed and co-related with dielectric, piezoelectric and proper adhesion of graphene sheet with polymer composites.

Creation of a PDMS Polymer Brush on SiO2-Based Nanoparticles by Surface-Initiated Ring-Opening Polymerization.

The incorporation of nanoparticles into soft matrices opens a broad spectrum of novel property combinations. However, one of the major challenges for these systems remains the compatibilization of particles with the surrounding matrix by proper surface functionalization. For silicon-based systems or liquid crystalline phases, polydimethylsiloxane (PDMS) brushes at the surface of particles increase the stability against particle agglomeration in such systems. Here, we report a novel approach for the functionalization of particles with a polysiloxane brush by surface-initiated ring-opening polymerization of a cyclosiloxane. For this purpose, surface hydroxy groups of silica and silica-coated hematite particles are used as initiators in combination with phosphazene bases as catalysts. The ring–chain equilibrium of a model-based solution polymerization is investigated in detail to find the appropriate reaction parameters. The corresponding molar masses are determined and compared by 1H-NMR and SEC measurements to confirm the underlying mechanism. In the resulting hybrid nanostructures, a covalently bound PDMS fraction is achieved up to 47 mass %.

Matching the Directions of Electric Fields from Triboelectric and Ferroelectric Charges in Nanogenerator Devices for Boosted Performance.

SummaryEmbedding additional ferroelectric dipoles in contacting polymer layers is known to enhance the performance of triboelectricnanogenerator (TENG) devices. However, the influence of dipoles formed between the triboelectric surface charges on two contacting ferroelectric films has been ignored in all relevant studies. We demonstrate that proper attention to the alignment of the distinct dipoles present between two contacting surfaces and in composite polymer/BaTiO3 ferroelectric films can lead to up to four times higher energy and power density output compared with cases when dipole arrangement is mismatched. For example, TENG device based on PVAc/BaTiO3 shows energy density increase from 32.4 μJ m−2 to 132.9 μJ m−2 when comparing devices with matched and mismatched dipoles. The presented strategy and understanding of resulting stronger electrostatic induction in the contacting layers enable the development of TENG devices with greatly enhanced properties.

Effect of ZIF-71 ligand-exchange surface modification on biofuel recovery through pervaporation

In this paper, zeolitic imidazolate framework-71 (ZIF-71) particles (~500 nm diameter) were modified with four different ligands through the solvent-assisted linker exchange (SALE) method. The objective of this was to assess the effect of ligand exchanged ZIF-71 on the performance of ZIF-71/polydimethylsiloxane (PDMS) mixed matrix membranes (MMMs) for removal of alcohol from dilute aqueous solutions. Both Fourier-transform infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy confirmed the exchange of the new ligands into the ZIF-71 material. The 1H NMR spectra demonstrated the molar ratios of the ligand-exchange into the ZIF-71 particles. X-ray diffraction and scanning electron microscopy results showed that the crystal structure and the morphology of ZIF-71 were maintained after the ligand-exchange modification process. Modified ZIF-71/PDMS composite membranes were synthesized to study the effect of ligand modification on alcohol/water separation performance. Ligand-modified ZIFs dispersed more evenly in the condensation cure PDMS polymer matrix than the unmodified ZIFs. The alcohol permeability and alcohol/water selectivity for ethanol and 1-butanol remained the same or decreased for membranes made with ligand-exchanged ZIF-71 particles.

A Comparative Study of Compressible and Conductive Vertically Aligned Carbon Nanotube Forest in Different Polymer Matrixes for High-Performance Piezoresistive Force Sensors.

In the present scenario, conducting and lightweight flexible polymer nanocomposites rival metallic and inorganic semiconducting materials as highly sensitive piezoresistive force sensors. Herein, we explore the feasibility of vertically aligned carbon nanotube (VACNT) nanocomposites impregnated in different polymer matrixes, envisioned as highly efficient piezoresistors in sensor applications. Polymer nanocomposites are selectively designed and fabricated using three different polymer matrixes, i.e., polydimethylsiloxane (PDMS), polyurethane (PU), and epoxy resins with ideal reinforcement of VACNTs to enhance the thermal stability, conductivity, compressibility, piezoresistivity, and sensitivity of these nanocomposites. To predict the best piezoresistive force sensor, we evaluated the structural, optical, thermal, electrical, mechanical, and piezoresistive properties of the nanocomposites using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), I-V measurements, compressive stress-strain measurements, hysteresis, sensitivity, and force studies. The results demonstrate that the PDMS/VACNT nanocomposite is capable of sustaining large force with almost complete recovery and enhanced sensitivity, thereby fulfilling the desirable need for a highly efficient conductive and flexible force sensor as compared to PU/VACNT and epoxy/VACNT nanocomposites.

Development of a Composite Material Based on Polymers Polydimethylsiloxane and Polytetrafluoroethylene Use in Human Prosthetic Coatings

The purpose of this study is the development of a composite material composed of a main layer of polydimethylsiloxane (PDMS) and a reinforcement of polytetrafluoroethylene (PTFE), to be used later in human prosthesis coatings. A mass ratio of the main layer consisting of PDMS:Tetraethyl orthosilicate (TEOS):Di-n-butyl tin dilaurate (DBTL) in the range of 33:1:0.5; 25:1:0.5; 10:1:0.5, and the mass ratio of the composite material (PTFE:PDMS) with a range was evaluated of 1:9; 1:1; 2:3. Obtaining the following results: Tensile strength of 0.085 MPa based on the ratio of 33:1:0.5 - 1:9 and 0.59 MPa with respect to the ratio of 10:1:0.5 - 2:3, evidencing an increase in tensile strength by decreasing the weight of PDMS and increasing the weight of PTFE. On the other hand, the composite material obtained is hydrophobic, insoluble in ethanol and water, has a cross-linking percentage of 98.74 % and 99.66 % respectively, also has a minimum permeance of 5.24x10-7 (g Pa-1 s-1 m-2). With which it is concluded that the treatment whose properties resemble the human skin is the combination 10:1:0.5 - 1:1 that allowed to obtain an average tensile strength of 0.66 MPa, average modulus of elasticity of 6.56 MPa, similar to the dermis of a 43 year old person.

Textured PDMS Films Applied to Thin Crystalline Silicon Solar Cells

Front surface texturization is a standard procedure used to improve optical properties of photovoltaic devices. In some particular cases, such as when dealing with ultrathin substrates, common texturization techniques can become unpractical or even unfeasible. Texturized polymer films applied on top of such devices may be used as an alternative. In this article, we report on the development of textured polydimethylsiloxane (PDMS) films to be placed on top of planar crystalline silicon solar cells based on thin substrates (≤40 μ m). The PDMS polymer is deposited onto a rough surface (conventional random pyramid textured silicon), cured and detached from it. By scanning electron microscope images, we demonstrate that the dilution of PDMS into toluene helps in a better replica of the master surface. Next, we apply the optimized PDMS films on top of dummy samples based on 10, 20, and 40 μm thick crystalline silicon (c-Si) substrates whose reflectance is significantly reduced after placing the PDMS films. Accurate optical simulations indicate that the optical improvement comes from three mechanisms: higher light transmission into the device, lower reflectance at the c-Si surface, and better light trapping properties at the thin c-Si absorber. Experimental verification of the optical improvement with texturized PDMS films is reported based on 40 μ m thick solar cell, where a short-circuit current density gain of 1.7 mA/cm2 is observed.

Nanocomposite film with green synthesized TiO2 nanoparticles and hydrophobic polydimethylsiloxane polymer: synthesis, characterization, and antibacterial test

Abstract The green synthesis of nanoparticles is of considerable interest because it is eco-friendly, cost-effective, biocompatible, and non-toxic. Split pulse extract was used as a reducing/capping agent for the synthesis of titanium dioxide (TiO2) nanoparticles. Green synthesized nanoparticles were embedded in the polydimethylsiloxane (PDMS) membrane by using a solution casting technique to develop a nanocomposite. This thin film was characterized using Fourier transform infrared spectroscopy, scanning probe microscopy, high-resolution scanning electron microscopy, ultraviolet-visible spectroscopy, and contact angle analysis. The antibacterial property of the TiO2/PDMS nanocomposite was examined, and the results showed excellent antibacterial activity of TiO2/PDMS compared to PDMS without nanoparticles. The nanocomposite film exhibited antibacterial activity against Gram-positive and Gram-negative bacteria in the presence of TiO2 nanoparticles in the polymer. Here, different weight percentages of TiO2 nanoparticles, i.e. 0%, 7%, 10%, and 13%, were loaded on the PDMS surface to enhance its antibacterial activity. The green synthesis of TiO2 nanoparticles embedded in PDMS and their suitability for antibacterial activity are reported for the first time.

Preparation of a self-healing silicone coating for inhibiting adhesion of benthic diatoms

This work reports a silicone coating (PDMS-UIa) with marine antifouling and self-healing properties, which was prepared by the first synthesis of polydimethylsiloxane polymer containing imine and urea groups and then adding a small amount of eco-friendly antifoulant. The characteristic structure of the polymer was verified via Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). The PDMS-UIa coating has rapid self-repairing performance, excellent transparency and the ability to control the release of antifouling agents at a certain rate. The adhesion experiment using four typical benthic diatoms indicated that the PDMS-UIa coating can effectively inhibit the attachment of diatoms, which effectively improves the static antifouling ability of silicone materials.

Facile One-Step Method to Fabricate a Slippery Lubricant-Infused Surface (LIS) with Self-Replenishment Properties for Anti-Icing Applications

In this work, a slippery lubricant-infused surface (LIS) was prepared by simple one-step mixing of polydimethylsiloxane (PDMS) resin and dimethyl silicone oil (PMX-200) directly. Silicone oil showed good compatibility with PDMS resin, and the added amount of silicone oil had no significant effect on the surface morphology of LIS. According to the results of surface observations, once the silicone oil film anchored on the LIS was removed, the silicone oil inside the PDMS polymer automatically diffused to the surface and formed a new silicone oil film again in a short time. Furthermore, with the increase of silicone oil content, the oil self-replenishment speed and amount of the LIS were enhanced, which also promoted a decrease of the surface water sliding angle and the improvement of the lubrication ability of the LIS. In the icing/deicing cycle tests, the slippery LIS still maintained very low ice adhesion strength after 24 cycles, showing excellent anti-icing performance.

Investigation of synergetic effect of PDMS polymer hydrophobicity and polystyrene-silica particles roughness in the content of microporous layer on water management in PEM fuel cell

Water management is still challenging issue in PEM fuel cells and many researchers have tried to elucidate the behavior of liquid water in cell media. Gas Diffusion Layer (GDL) or Microporous Layer (MPL) are usually chosen to modify their surfaces with hydrophobic materials for better water removal ability. Distinctly, this study deals with using both hydrophobicity of polydimethylsiloxane (PDMS) and roughness of polystyrene (PS) - silica particles together in the content of MPL. The best fuel cell performance was obtained with the MPL included binary of PDMS-1 (3% wt.) and PS-silica (1% wt.) particles. The highest current density value of this MPL was recorded as 287.5 mA/cm2 (@0.6 V) which is corresponded to the 172 mW/cm2 power density with 0.1 mg Pt/cm2 catalyst loading. Contact angle and avearge surface roughness were respectively measured as 122° ± 4.7 and 2.63 µm for the mentioned MPL. It was assumed that optimum hydrophobicity and surface roughness distinguished this MPL from the other prepared MPLs in terms of PEM fuel cell performance.

Detection of Nicotine Effect on Colon Cells in a Plasmonic Platform.

Introduction: Smoking as one of the causes of various diseases has encouraged worldwide studies on its adverse pharmacological effects on different organs. Nicotine may influence the smooth muscles of the colon and subsequently the gut motility, which leads to a change in the moving rate of digested material through the gastrointestinal tract. Methods: Among various techniques, optical detection methods benefit from non-contact and highsensitivity for studying the early effect of nicotine on the cells. Thus, we used an optically ellipsometric method to get the fast and sensitive nicotine effect on the colon cell. Two-dimensional plasmonic platforms by gold deposition onto the polydimethylsiloxane polymer (PDMS) patterned substrate were used as the guest medium of the cell and the sample was excited by all of the visible region wavelengths at different exposure time and maintenance time. Results: Our results showed that the phase difference between each polarization increased by augmenting the exposure time of smoke over the cell at a fixed maintenance time and there was a general red-shift by increasing the maintenance time at a fixed exposure time. Conclusion: Using different exposure time to cigarette smoke, we optically showed that the cigarette containing the addicting chemical of nicotine had a direct effect on the cultured colon cells on our 2D biocompatible plasmonic chip. It demonstrated considerable changes in the amplitude and phase of the interacted light by injecting nicotine into the system with the aid of the label-free and non-invasive plasmonic technique.

Robust superhydrophobic SiO2/polydimethylsiloxane films coated on mild steel for corrosion protection

One of the biggest obstacles for superhydrophobic films in applications is their poor mechanical resistance. In this research, robust superhydrophobic SiO2 films were constructed on mild steel (MS) for corrosion protection by the combination of rough electrodeposited SiO2 (E-SiO2) films and durable polydimethylsiloxane (PDMS) polymer with low surface energy. Results show that the PDMS content has a great effect on the microtopography, wettability, roughness, and wear-resistance of the final films. EIS measurements indicate that as-prepared robust superhydrophobic E-SiO2/PDMS films exhibit good corrosion inhibition efficiency of up to 99.99 % for MS substrates in 3.5 wt.% NaCl solution.