Amount Of Polydimethylsiloxane Research Articles

Enhancing hydrophobicity through polydimethylsiloxane-blended poly(vinylidene fluoride-co-hexafluoropropylene) electrospun membranes: A well-designed approach

With the growing environmental concerns over the use of chemicals and nanomaterials to achieve membrane hydrophobicity, polydimethylsiloxane (PDMS) has emerged as a sustainable and eco-conscious alternative. Introducing PDMS into the doping solution to be used for electrospinning is a simple yet highly efficient means of augmenting the hydrophobicity of the electrospun membrane. Nevertheless, to achieve stable nanofibers and an appropriate structure as a membrane when using PDMS introduction, it is imperative to regulate the polymer concentration. In the present investigation, we explored modifications in the physicochemical characteristics of the membrane, specifically changes in hydrophobicity, upon the addition of PDMS to a 15 % poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) solution. Increasing the amount of PDMS was found to introduce more CH3 groups to the membrane's surface, but it also had the side effect of enlarging the fiber diameter. Thus, the maximum contact angle improved to 148° with the addition of 10 % PDMS. However, the membrane distillation system using the membrane that included 5 % PDMS exhibited the most stable performance, as it sustained continuous operation for more than 170 h and effectively prevented membrane wetting.

Polydimethylsiloxane-coated macroporous silica adsorbent in thermal desorption gas chromatography

Polydimethylsiloxane (PDMS)-coated macroporous silica (MPSi) particles were developed for the extraction of volatile organic compounds (VOCs) from air samples in thermal desorption-gas chromatographic analysis. The gas sample was collected by a gas sampling pump at 100 mL/min. Different amounts of PDMS coating were prepared, and the fundamental extraction and desorption performances were investigated using even numbered n-alkanes of C8–C28. The extraction efficiency increased by increasing PDMS coating, and the desorption efficiency showed more than 99% at a desorption temperature of 310°C for all the investigated adsorbents. This remarkable desorption performance showed a higher peak area of the analytes than that of the Tenax TA-packed thermal desorption tube, especially for higher molecular weight compounds. Furthermore, an activated carbon particle of Carbopack X was introduced on the latter side of the PDMS-MPSi to extract low-molecular weight compounds. This double-bed-type extraction tube showed a successful determination of a wide range of VOCs. The double-bed-type extraction tube was then applied to the extraction of VOCs related to sick building syndrome (SBS). The results for the extraction and desorption performances of the SBS-related VOCs were well agreed with that of alkanes, and the applicability of the extraction tube to the determination of other types of conventional VOCs were confirmed.

Block copolymer functionalized quartz fibers/cyanate ester wave-transparent laminated composites

A block copolymer of PDMS- b -PGMA is synthesized by polymerizing glycidyl methacrylate (GMA) via reversible addition-fragmentation chain transfer (RAFT) polymerization applying a polydimethylsiloxane (PDMS) based macro-RAFT agent, which is then performed to functionalize the quartz fibers (QFs@PDMS- b -PGMA) via a simple coating process. Finally, the QFs@PDMS- b -PGMA/bisphenol A dicyanate ester (BADCy) wave-transparent laminated composites are fabricated by high-temperature molding. Nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and size exclusion chromatography (SEC) demonstrate the successful preparation of PDMS- b -PGMA with expected structure. When the molar mass and coating amount of PDMS- b -PGMA are respectively 8100 g/mol and 2.0 wt.%, QFs@PDMS- b -PGMA/BADCy wave-transparent laminated composites present optimal mechanical properties and wave-transparent performance. The interlaminar shear strength (ILSS) and flexural strength are 53.6 and 552.0 MPa, respectively. Meanwhile, the dielectric constant and dielectric loss values are 2.61 and 0.0028 at 1 MHz (wave transmittance of 93.8%), showing good stability at different frequencies (10 2 -10 6 Hz and 8.4-12.4 GHz) and temperatures (25-250 °C).

SiO2-PDMS as oil removal system

This work presents an oil removal system design based on the use of hydrophobic silica (SiO2/PDMS) obtained by the co-condensation of silica with polydimethylsiloxane (PDMS) using DBTL as a polycondensation catalyst. The amount of PDMS in the SiO2/PDMS structure varied from 10 to 40%w. The SiO2/PDMS was impregnated into a sponge system and the amount of hydrophobic silica trapped in the sponge was evaluated by gravimetry; in addition, infrared spectroscopy will allow the identification of the hydrophobic silica in the sponge and the main functional groups of the sponge. The hydrophobic character was determined by changing the water absorption capacity of the sponge and by measuring the contact angle. On the other hand, optical microscopy allowed the identification of changes in the sponge surface due to the presence of SiO2/PDMS. Finally, the effect of the amount of PDMS on the oil-in-water removal capacity was determined.

Novel Reproducible Manufacturing and Reversible Sealing Method for Microfluidic Devices.

Conventional manufacturing methods for polydimethylsiloxane (PDMS)-based microdevices require multiple steps and elements that increase cost and production time. Also, these PDMS microdevices are mostly limited to single use, and it is difficult to recover the contents inside the microchannels or perform advanced microscopy visualization due to their irreversible sealing method. Herein, we developed a novel manufacturing method based on polymethylmethacrylate (PMMA) plates adjusted using a mechanical pressure-based system. One conformation of the PMMA plate assembly system allows the reproducible manufacture of PDMS replicas, reducing the cost since a precise amount of PDMS is used, and the PDMS replicas show uniform dimensions. A second form of assembling the PMMA plates permits pressure-based sealing of the PDMS layer with a glass base. By reversibly sealing the microdevice without using plasma for bonding, we achieve chip on/off configurations, which allow the user to open and close the device and reuse it in an easy-to-use way. No deformation was observed on the structures of the PDMS microchannels when a range of 10 to 18 kPa pressure was applied using the technique. Furthermore, the functionality of the proposed system was successfully validated by the generation of microdroplets with reused microdevices via three repetitions.

A sensitivity-enhanced temperature sensor with end-coated PDMS in few mode fiber based on vernier effect

In this paper, a few mode fiber temperature sensor based on vernier effect is proposed. The sensor consists of two cascaded microcavities and realizes temperature sensing based on vernier effect. The single mode fiber(SMF) and few mode fiber(FMF) are fixed by a capillary glass tube to form an air reference microcavity. The end of the FMF is dipped with an appropriate amount of polydimethylsiloxane(PDMS) to form a sensing microcavity with a certain thickness, which is an air microcavity-FMF–PDMS structure. Due to the different refractive index of each medium, the light is reflected on the four critical surfaces, and the four reflected light beams interfere, the vernier effect is formed by adjusting the microcavity length to a suitable length. When the external temperature changes, the microcavity length and refractive index of PDMS change, which leads to the change of interference spectrum. Therefore, the high sensitivity measurement of temperature can be realized by the change of reflection spectrum. The temperature characteristics of the sensor are studied experimentally. The results show that the temperature sensitivity is significantly improved compared with the traditional single microcavity sensor. In the temperature range of 35°C∼45°C, the temperature sensitivity can reach 4.7nm/°C, and the linearity is very good. The sensor has the advantages of compact structure, simple fabrication and high sensitivity, so it has wide application prospects in the field of temperature sensing.

Impact of PDMS-Based Microfluidics on Belousov-Zhabotinsky Chemical Oscillators.

Sub-nanoliter volumes of the Belousov-Zhabotinsky (BZ) reaction are sealed in microfluidic devices made from polydimethylsiloxane (PDMS). Bromine, which is a BZ reaction intermediate that participates in the inhibitory pathway of the reaction, is known to permeate into PDMS, and it has been suggested that PDMS and bromine can react ( J. Phys. Chem. A. 108, 2004, 1325-1332). We characterize the extent to which PDMS affects BZ oscillations by varying the volume of the PDMS surrounding the BZ reactors. We measure how the oscillation period varies with PDMS volume and compare with a theoretical reaction-diffusion model, concluding that bromine reacts with PDMS. We demonstrate that minimizing the amount of PDMS by making the samples as thin as possible maximizes the number of oscillations before the BZ reaction reaches equilibrium and ceases to oscillate. We also demonstrate that the deleterious effects of the PDMS-BZ interactions are somewhat mitigated by imposing constant chemical boundary conditions through using a light-sensitive catalyst, ruthenium, in combination with patterned illumination. Furthermore, we show that light can modulate the frequency and phase of the BZ oscillators contained in a PDMS matrix by 20-30%.

Water management improvement in PEM fuel cells via addition of PDMS or APTES polymers to the catalyst layer.

Water management is one of the obstacles in the development and commercialization of proton exchange membrane fuel cells (PEMFCs). Sufficient humidification of the membrane directly affects the PEM fuel cell performance. Therefore, 2 different hydrophobic polymers, polydimethylsiloxane (PDMS) and (3-Aminopropyl) triethoxysilane (APTES), were tested at different percentages (5, 10, and 20 wt.%) in the catalyst layer. The solution was loaded onto the surface of a 25 BC gas diffusion layer (GDL) via the spraying method. The performance of the obtained fuel cells was compared with the performance of the commercial catalyst. Characterizations of each surface, including different amounts of PDMS and APTES, were performed via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses. Molecular bond characterization was examined via Fourier transform infrared spectroscopy (FTIR) analysis and surface hydrophobicity was measured via contact angle measurements. The performance of the fuel cells was evaluated at the PEM fuel cell test station and the 2 hydrophobic polymers were compared. Surfaces containing APTES were found to be more hydrophobic. Fuel cells with PDMS performed better when compared to those with APTES. Fuel cells with 5wt.% APTES with a current density of 321.31 mA/cm 2 and power density of 0.191 W/cm 2 , and 10wt.% PDMS with a current density of 344.52 mA/cm 2 and power density of 0.205 W/cm 2 were the best performing fuel cells at 0.6V.

PVA-PDMS-Stearic acid composite nanofibrous mats with improved mechanical behavior for selective filtering applications

In this work, we report a facile way to fabricate composite nanofibrous mats of polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS), and stearic acid (SA) by employing the electrospinning-technique, with PDMS fraction ranging from 40w% to nearly 80w%. The results show that for a predetermined fraction of PVA and SA, incorporation of an optimal amount of PDMS is necessary for which the mats exhibit the best mechanical behavior. Beyond this optimal PDMS fraction, the mechanical properties of the composite mats deteriorate. This result has been attributed to the ability of the SA molecules to mediate binding between the PVA and PDMS long-chain molecules via van-der-Waals bonding. The morphological, structural, mechanical, and thermal characterizations respectively using SEM, XRD, DMA/tensile test, and DSC lend support to this explanation. By this method, it is possible to control the hydrophilicity/oleophilicity of the mats, and the mats show an excellent selective permeability to oil as compared to water and successfully filter water from a water-in-oil emulsion. Incorporation of SA not only serves to aid in electrospinning of a PDMS-rich nanofibrous mat with good mechanical strength and control over hydrophilicity/oleophilicity, but also has a potential use in fabricating sheets impregnated with phase change materials for thermal energy storage.

Persistence of Polydimethylsiloxane Condom Lubricants.

Polydimethylsiloxane (PDMS) is commonly used to lubricate condoms. The detection of PDMS on swabs from complainants can be used to support an allegation of sexual assault. Previous research has focused on establishing analytical techniques for detecting PDMS. This research examined the persistence of PDMS on the penis, in the vagina, in the mouth, and on skin. The longest PDMS detection times were 20h on the penis, 35h in the vagina, and 52h on skin. PDMS was detected up to 4h in the mouth if the participant did not eat or drink and up to 9h if the participant slept. PDMS was not detected in the mouth after eating or drinking. The presence of biological fluids had no detrimental effect on the analysis. Aqueous extraction of swabs for DNA did not remove any significant amount of PDMS; hence, swab remains could be subsequently analyzed for PDMS.

Synthesis of Polydimethylsiloxane-Modified Polyurethane and the Structure and Properties of Its Antifouling Coatings

Polydimethylsiloxane (PDMS) could be used to improve the antifouling properties of the fouling release coatings based on polyurethane (PU). A series of polydimethylsiloxane-modified polyurethane coatings were synthesized with various PDMS contents, using the solvent-free method. The effects of PDMS content and seawater immersion on the chain structure and surface morphology were investigated by confocal laser scanning microscopy (CLSM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Based on the measurements of contact angles of deionized water and diiodomethane, surface free energies of the coatings were estimated according to the Owens two-liquid method. The PDMS-modified polyurethane exhibited lower surface free energy and a lower glass transition temperature than polyurethane. The presence of PDMS increased the degree of microphase separation, and enhanced the water resistance of the coatings. The optimum amount of PDMS reduced the elastic modulus and increased the ductility of the coating. The presence of PDMS benefited the removal of weakly attached organisms. Panel tests in the Yellow Sea demonstrated the antifouling activity of the PDMS-modified polyurethane.

Simultaneous Improvement of Oxidative and Hydrolytic Resistance of Polycarbonate Urethanes Based on Polydimethylsiloxane/Poly(hexamethylene carbonate) Mixed Macrodiols.

The degradation behaviors including oxidation and hydrolysis of silicone modified polycarbonate urethanes were thoroughly investigated. These polyurethanes were based on polyhexamethylene carbonate (PHMC)/polydimethylsiloxane (PDMS) mixed macrodiols with molar ratio of PDMS ranging from 5% to 30%. It was proved that PDMS tended to migrate toward surface and even a small amount of PDMS could form a silicone-like surface. Macrophages-mediated oxidation process indicated that the PDMS surface layer was desirable to protect the fragile soft PHMC from the attack of degradative species. Hydrolysis process was probed in detail after immersing in boiling buffered water using combined analytical tools. Hydrolytically stable PDMS could act as protective shields for the bulk to hinder the chain scission of polycarbonate carbonyls whereas the hydrolysis of urethane linkages was less affected. Although the promoted phase separation at higher PDMS fractions lead to possible physical defects and mechanical compromise after degradation, simultaneously enhanced oxidation and hydrolysis resistance could be achieved for the polyurethanes with proper PDMS incorporation.

Mechanical Properties of Ultralow Density Graphene Oxide/Polydimethylsiloxane Foams

ABSTRACTLow-density, highly porous graphene/graphene oxide (GO) based-foams have shown high performance in energy absorption applications, even under high compressive deformations. In general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. In the case of graphene-based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and/or GO electronic and mechanical properties. Despite the attractive physical properties of graphene/GO based-foams, their structural and thermal stabilities are still a problem for some applications. For instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. Recently, a new and scalable synthetic approach to produce low-density 3D macroscopic GO structure interconnected with polydimethylsiloxane (PDMS) polymeric chains (pGO) was proposed. A controlled amount of PDMS is infused into the freeze-dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like a glue bonding PDMS and GO sheets. In order to obtain further insights on mechanisms behind the enhanced mechanical pGO response we carried out fully atomistic molecular dynamics (MD) simulations. Based on MD results, we build up a structural model that can explain the experimentally observed mechanical behavior.

High Toughness in Ultralow Density Graphene Oxide Foam

Here, the scalable synthesis of low‐density 3D macroscopic structure of graphene oxide (GO) interconnected with polydimethylsiloxane (PDMS) is reported. A controlled amount of PDMS is infused into the freeze‐dried foam to result into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. The PDMS wets the graphene oxide sheets and acts like glue between the 2D sheets. Molecular dynamics simulations are used to further elucidate the mechanisms of the interactions of graphene oxide layers with PDMS. The ability of using the interconnecting graphene oxide foam as an effective oil–water separator and stable insulating behavior to elevated temperatures are further demonstrated. The structural rigidity of the sample is also tested using laser impact and compared with GO foam.

Atomic force microscopy technique for the surface characterization of sol–gel derived multi-component silica nanocomposites

Sol–gel derived multi-component silica nanocomposites are widely accepted as materials in a host of medical applications including bioactive drug carriers. In this paper, both the effect of polydimethylsiloxane (PDMS) (20, 25, and 30wt.%) on nanometre-scale phase separation and the surface properties of sol–gel processed polydimethylsiloxane/calcium phosphate/silica (PDMS-modified CaP/SiO2) are reported. The evaporation-induced self-assembly (EISA) technique was used to prepare the solid films of multicomponent silica nanocomposites. Atomic force microscopy (AFM) in PeakForce quantitative nanomechanical mapping (PF-QNM) mode was used to examine the surface heterogeneity including morphology, surface roughness, adhesion and elasticity of the composites structure on the nanometre-scale. The resulting materials were nanoscopically phase separated, but macroscopically uniform. PF-QNM results revealed the presence of elastic domains of PDMS-rich nanophase and rigid domains belonging to bioactive silica-rich nanophases. The nanophase separation depends on the amount of PDMS. This effect was correlated with an increase in the adhesion force, mean roughness (Ra) and root mean square roughness (Rq) and a decrease in the Young’s modulus in the composites as a function of PDMS content. The statistical analyses of these results showed significant differences between nanocomposites with different amounts of PDMS. The best compatibility and the nanophase dispersion were observed for 20% of PDMS in the nanocomposite’s structure.

Comment on: "Analysis of Silicones Released from Household Items and Baby Articles by Direct Analysis in Real Time-Mass Spectrometry" by Jürgen H. Gross. J. Am. Soc. Mass Spectrom. 26, 511-521 (2015).

In a recent paper, Gross [1] reported the release of silicone oligomers from articles of daily use by their exposure to a direct analysis in real time (DART) ion source and expressed concern for a substantial dose of silicones available for human intake. Although the results of the article clearly demonstrate that DART-MS may be used as a qualitative tool to identify silicone rubbers, there appear to be major errors introduced to the quantitation of silicone species by the calibration method employed. Additionally, the report considerably understates that the amount of polydimethylsiloxane (PDMS) observed after exposure of silicone materials directly to the DART source at 300 °C is substantially higher than what is released under normal use conditions.

Study on the Preparation and Properties of Colored Iron Oxide Thin Films

Colored iron oxide thin films were prepared using Sol-gel technique. The raw materials were tetraethyl orthosilicate (TEOS), etoh ehanol (EtOH), iron nitrate, and de-ionized water. Various properties were measured and analysed, including the colour of thin films, surface topography, UV-Visible spectra, corrosion resistance and hydrophobicity. To understand how these properties influenced the structural and optical properties of Fe2O3 thin films, Scanning Electron Microscope (SEM), UV Spectrophotometer and other facilities were employed. Many parameters influence the performance of thin films, such as film layers, added H2O content, and the amount of polydimethylsiloxane (PDMS). When the volume ratio of TEOS, EtOH and H2O was 15: 13: 1, the quality of Fe(NO3)3·9H2O was 6g, and pH value was 3, reddish and uniform Fe2O3 thin films with excellent properties were produced. Obtained thin films possessed corrosion resistance in hydrochloric acid with pH=l and the absorption edge wavelength was ~350.2nm. Different H2O contents could result in different morphologies of Fe2O3 nanoparticles. When 1.5 ml PDMS was added into the Sol, thin films possessed hydrophobiliry without dropping. Coating with different layers, thin films appeared different morphologies. Meanwhile, with the increment of film layers, the absorbance increased gradually.

Effect of copolymerizing fluorine‐bearing monomers on the relationship among internal structure, gas permeability, and transparency in copolymer networks composed of methacrylates and siloxane macromers

AbstractTo clarify the effect of the type of acrylic monomer and the molecular weight (Mn) of polydimethylsiloxane (PDMS) on the relationship among the internal structure, oxygen permeability coefficient [P(O2)] and transparency, crosslinked copolymers were prepared with two different acrylic monomers : methyl methacrylate (MMA) and trifluoroethyl methacrylate (TFEMA). PDMS macromers with Mn of 1700, 3300, 4700, and 7800 g/mol were used. DSC measurements suggested that all constituent phases were insoluble with each other. The Mn of PDMS affected both the light transmittance and P(O2). The relationship between the Mn and P(O2) over the low Mn range (1700 and 3300 g/mol), and the calculated PDMS domain size ratio, were found to support the [Mn]2/3 rule into the crosslinked copolymer. Furthermore, a 3300 g/mol Mn copolymer became transparent when the amount of PDMS was greater than PMMA. In addition, copolymerization with TFEMA drastically affected those properties, and this effect was much greater than the effect of the PDMS Mn. To clarify the mechanism of P(O2) improvement induced by TFEMA copolymerization, calculations on the relationship among the P(O2), PDMS volume fraction, and morphology model were performed, and some properties such as solubility parameters should play important roles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Improved soiling resistance of polypropylene fibers on the addition of synthetic compounds

With the aim of enhancing the soil resistance of polypropylene (PP) fibers, polydimethylsiloxane (PDMS) and/or oleamide (OA) were added, and the soiling and wear resistances of the obtained fibers were evaluated. Films made from PP with the addition of PDMS and/or OA were fabricated and their water repellencies were evaluated by using droplets to measure their contact angles. The water contact angle increased with increasing amount of PDMS and/or OA added to PP. These blended resins were then used to produce fibers, which were in turn used to form fabrics. The soil resistances of these fabrics were evaluated by immersing them in aqueous solutions of a water-soluble artificial soiling substance for 1 min. Fiber G, for which both PDMS and OA had been added to PP, had a soiling ratio that was about 8–15% lower than that of pure PP fibers to which nothing had been added. Longer immersion of 24 h resulted in Fiber E, for which only PDMS had been added, having the lowest soiling ratio. In contrast, Fibers L and G (produced by adding OA) had relatively high soiling ratios when immersed for a long time. The wear resistances of knitted fabrics were evaluated using an abrasion tester. Fabric made from pure PP fibers had holes after 20 cycles of abrasion, whereas fabrics formed from fibers to which PDMS and/or OA had been added did not have holes even after 100 cycles of abrasion, which represents a remarkable improvement in wear resistance.

Analysis and improvement on frequency sensitivity of series photodetector frequency circuit system and its application for HEX fluorescence measurement

This study reported the improvement of frequency sensitivity of series photodetector frequency circuit system for fluorescence detection. The 48 MHz series photodetector frequency circuit system matched with polydimethyl siloxane (PDMS) focusing lens was applied to the detection of emissive fluorescence intensity. MEMS technology processes were used to fabricate PDMS focusing lens, the mixing amount of PDMS and the curing temperature were adjusted, and self-improved mold-transfer technology was used to make a 3D planar lens of diameter of 3 to 10 mm. While the series photodetector frequency circuit system matched with PDMS focusing lens of diameter 10 mm was used for fluorescence detection, the relative fluorescence intensity was enhanced by approximately two times, which indicated that the frequency sensitivity of the 48 MHz sensor system was improved. Besides, the bias of the photodetector was also adjusted to improve the frequency sensitivity. According to the optimal conditions of PDMS focusing lens and bias of a photodetector, the detection limit of HEX fluorescence dye concentration 3.3 pmol/L can be measured. The results of the fluorescence experiment also demonstrated that the frequency shift of the 48 MHz sensor system was linearly related to the logarithm of fluorescence dye concentration from 333.3 nmol/L to 3.3 pmol/L.