Pervaporation Characteristics in Removal of Benzene from Water through Polystyrene-Poly (Dimethylsiloxane) IPN Membranes

This paper focuses on the effects of the PSt content of polystyrene (PSt)-poly (dimethylsiloxane) (PDMS) interpenetrateing network (IPN) polymer membranes, on the pervaporation (PV) characteristics during the removal of benzene from an aqueous solution of dilute benzene. When an aqueous solution of 0.05wt% benzene was permeated through the PSt-PDMS IPN membranes, they showed high benzene/water selectivity. Both the permeability and the benzene/water selectivity of the membranes were enhanced with increasing PSt content in the PSt-PDMS IPN membrane. The physicochemical mechanism of permeation and separation through the PSt-PDMS IPN membranes during PV is also discussed. The best normalized permeation rate, separation factor for benzene selectivity, and PV separation index of the PSt-PDMS IPN membrane were 1.27 × 10-6 kgm (m2hr)-1, 3293, and 41821, respectively. These PV characteristics are discussed from the viewpoint of the chemical and physical structure of the PSt-PDMS IPN membranes.

CONFIGURATION-DEPENDENT PROPERTIES OF POLY(DIMETHYLSILOXANE) CHAIN

The intermolecular rotational potential energies for poly(dimethylsiloxane) (PDMS) chains are directly obtained from a priori probability P-alpha beta. Here the differing statistical weight matrices for the Si-O and O-Si bonds are considered in calculating the configuration partition function. In the Bahar's model, as the same statistical weight matrices for the Si-O and O-Si bonds are adopted, there exists a large deviation of a priori probability P-alpha beta between the theory and the molecular dynamics (MD) simulation. Our model gives satisfactory agreement with experiment on the mean-square unperturbed end-to-end distance, the mean-square dipole moment and its temperature dependence, and the molar cyclization equilibrium constants for dimethylsiloxane oligomers. This new rotational isomeric state approach can be widely applied to other chains; such as -CH2-C[(CH2)(m)H](2)- and -O-Si[(CH2)(m)H](2) for arbitrary m.

A Flexible Pressure Sensor Based on Poly(dimethylsiloxane) Nanostructures Film

This paper proposed a flexible pressure sensor based on poly(dimethylsiloxane) nanostructures film and report an efficient,simple,and low-cost fabrication strategy via soft nanoimprint lithography.The pressure sensor can convert external pressure or mechanical deformation into electrical signal to detect pressure and strain changes based on the coupling of triboelectrification and electrostatic induction.To enhance the performance of the pressure sensor,it consists of sub-500 nm resolution on the surface of elastic poly(dimethylsiloxane) sensitive layer and an indium tin oxide electrode thin film.When the pressure applied on the nanostructures layer,triboelectrostatic charges are induced.In the experiment,it measures up to sensitivity of 0.8 V/kPa at frequency of 5 Hz.This study results in potential applications such as wearable smart devices and skin-attachable diagnostics sensing systems.

Mechanical, Thermal and Morphology Properties of Thermoplastic Polyurethane Copolymers Incorporating α,ω-Dihydroxy-[poly(propyleneoxide)-poly (dimethylsiloxane)-poly(propyleneoxide)] of Varying Poly(propyleneoxide) Molecular Weight

Novel segmented thermoplastic polyurethane (TPU) copolymers were synthesized using two-step solventless bulk polymerization. 4,4’-methylenediphenyl diisocyanate (MDI) and 1,4-Butanediol (BDO) were used to form hard segment of TPU and α,ω-dihydroxy-[poly(propyleneoxide)-poly (dimethylsiloxane)-poly(propyleneoxide)] (α,ω-dihydroxy-(PPO-PDMS-PPO)) was used to form soft segment of TPU, where the molar ratio of the –N=C=O/OH was 1.02 and the hard segment weight percentage was 30%. A series of TPUs were characterized by fourier transform infrared spectroscopy (FT-IR). The investigation of triblock oligomer’s PPO molecular weight impact on the derived TPU’s mechanical properties, thermal performance, surface water repellency and morphology performance was carried by Instron material tester, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angles (WCA), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM-EDX) and wide angle X-ray diffraction (WAXD), respectively. FT-IR confirmed α,ω-dihydroxy-(PPO-PDMS-PPO) well cooperating into urethane structure and analyzed hydrogen bonding between N-H group with hard segment C=O group and N-H group with soft segment C-O-C group. DSC and WAXD results showed α,ω-dihydroxy-(PPO-PDMS-PPO) segments crystallization. SEM-EDX results showed that the presence of a spherulitic morphology, which arose from the crystallization of the PPO segments. The thermal properties measured by TGA and DSC were slightly affected by molecular weight of PPO and microphase separation. The weight loss of TPUs started between 294°C and 300°C, and Tg was in the range of -70°C to -107°C. TPU copolymers’ surface hydrophobicity property was excellent with WCA range of 95°?to 112°. TPU-3 with 1000 molecular weight PPO has the optimized mechanical properties with tensile strength 16.4 MPa and the modulus at 100% elongation 6.2 MPa and elongation 398%.

Inhibition of sulfate-reducing bacteria influenced corrosion on hydrophobic poly(dimethylsiloxane)coatings

Sulfate-reducing bacteria(SRB)has been pointed out as one of the causative agents of microbial induced corrosion in the marine environment.To address this problem,novel strategies are being experimented as against the earlier methods which have been banned due to their toxic effects on useful aquatic lives.Thus,the aim of this study was to investigate the effect of non-toxic perfluorodecyltrichlorosilane(PFDTS)on resistance of hydrophobic poly(dimethylsiloxane)/phosphoric acid-treated zinc oxide(PDMS/PA-treated ZnO)coatings to SRB-induced biofouling and corrosion.The surface features of the coatings before and after exposure to SRB/NaCl solution were analyzed by scanning electron microscopy(SEM).Wettability of the coatings before and after exposure was also measured.The interaction of SRB with the coatings was investigated by FTIR spectroscopy.The resistance performance of the modified coatings against SRB-induced corrosion was monitored by electrochemical impedance spectroscopy(EIS).The EIS measurements revealed that 0.20 g PFDTS-based coating displayed highest corrosion resistance with impedance modulus of 6.301×10^10 after 15 d of exposure to SRB/NaCl medium.The results were corroborated by surface and chemical interaction analyses,and thus,indicate that 0.20 g PFDTSmodified PDMS/PA-treated ZnO coating has potentials for excellent SRB-induced corrosion resistance and anti-biofouling performance.

Poly dimethylsiloxane/carbon nanofiber nanocomposites: fabrication and characterization of electrical and thermal properties

This article presents the fabrication and characterization of poly dimethylsiloxane/carbon nanofiber(CNF)-based nanocomposites.Although silica and carbon nanoparticles have been traditionally used to reinforce mechanical properties in PDMS matrix nanocom-posites,this article focuses on understanding their impacts on electrical and thermal properties.By adjusting both the silica and CNF concentrations,12 different nanocomposite formulations were studied,and the thermal and electrical properties of these materials were experimentally characterized.The developed nano-composites were prepared using a solvent-assisted method pro-viding uniform dispersion of the CNFs in the polymer matrix.Scanning electron microscopy was employed to determine the dispersion of the CNFs at different length scales.The thermal properties,such as thermal stability and thermal diffusivity,of the developed nanocomposites were studied using thermogravi-metirc and laser flash techniques.Furthermore,the electrical volume conductivity of each type of nanocomposite was tested using the four-probe method to eliminate the effects of contact electrical resistance during measurement.Experimental results showed that both CNFs and silica were able to impact on the overall properties of the synthesized PDMS/CNF nanocomposites.The developed nanocomposites have the potential to be applied to the development of new load sensors in the future.

Poly（dimethylsiloxane） Microchips with Two Sharpened Stretching Tips and Its Application to Protein Separation Using Dynamic Coating

An integrated poly（dirnethylsiloxane） （PDMS） microchip with two sharpened stretching tips for convenient sample injecting, running buffer refreshing and channel cleaning has been presented. The sample was directly introduced into the separation channel through the stretching inlet tip without complicated power switching supplies and injection cross channel. The operation of running buffer refreshing or channel cleaning was simplified by vacuuming one end of the tip and placing the other tip into the solution vial. Therefore, this fabrication method can be easily applied to most analytical laboratories economically without soft lithography and plasma bonding equipments. The attractive performance of the novel PDMS microchips has been demonstrated by using laser-induced fluorescence detection for separation of proteins. The addition of 0.04% Brij 35 in 0.04 mol/L phosphate buffer （pH 7.0） can reduce the adhesion of proteins in multienzyme tablet and make separation more easily. The electroosmotic flow （EOF） exhibits pH-independence in the range of 3-1 1 in dynamic modified microchannel.

A robust mechanochromic self-healing poly(dimethylsiloxane)elastomer

Simultaneously introducing mechanochromic and self-healing properties into polymers is almost a field unexplored,and the integration of these capabilities in one material has important theoretical and substantial significance.In this paper,a mechanochromic poly(dimethylsiloxane)(PDMS)elastomer with self-healing ability and superior mechanical properties is first reported.Spiropyran mechanophore and reversible hydrogen bonds are incorporated into the system to realize multi-stimuliinduced color change and self-healing ability,respectively.Upon uniaxial stretching,heating or UV irradiation,the elastomer exhibits a reversible color variation from yellow to purple,which can recover rapidly by white light illumination.Its excellent tensile strength(10.5 MPa)and elongation at break(785%)are distinctive among PDMS elastomers with no fillers.After heat treatment at 60℃for 24 h,the self-healing efficiency of strength can achieve 92.1%.This novel robust PDMS elastomer holds great promise for applications in visualized stress/strain sensing,self-healing biomaterials and wearable devices.

Highly Sensitive Chemiluminescence Detection for PDMS/GIass Micro-chip Electrophoresis

This paper described a highly sensitive chemiluminescence detection system for micro-chip electrophoresis (MCE) based on luminol-hydrogen peroxide reaction catalyzed by the metal ions. The micro-chip was composed of poly(dimethylsiloxane) (PDMS) and glass, and was fabricated by micro-machining technology. The surface of channels was dynamically modified by polydimethylacrylamide (PDMA) in order to eliminate unhomogeneous electroosmotic flow (EOF) of the PDMS/glass chip, adsorption of molecules, and improve hydrophobicity on PDMS surface. The detection modes, reagent mix procedures and reaction conditions were optimized and the detection limit of 5×10 mol/L for cobalt (II) was achieved by MCE with chemiluminescence detection, which was about four orders of magnitude more sensitive than that reported in the reference.

Determination of Specific Refractive Index Increment (dn/dc)_μ at a Constant Chemical Potential,for Solutions of Polymer in Mixed Solvents by the GPC Method

A new chromatographic method is described for the determination of specific refractive index increment（dn/dc）μ at a constant chemical potential,for polymer/mixed solvent systems.In this method the（dn/dc）is obtained by measuring the areas of solvated-polymer peaks when the mixed solvent is used as an eluent.Values of（dn/dc）μ for the poly（dimethylsiloxane）（PDMS）-benzene-methanol system,determined by the proposed method are in good agreement with those determined by the conventional dialysis method.The new approach has the advantages of simplicity,fast speed,and high reproducibility.The experimental results for stearic acid-chloroform-methanol system show that this method can also be applied to nonpolymer/mixed solvent systems for the determination of（dn/dc）μ.

CuSO_4 Micro-crystal Lattice Produced by Microcontact Printing

An elastic stamp was produced by molding poly(dimethylsiloxane)(PDMS) against a master with micro\|patterns on the surface. Then a procedure named microcontact printing was carried out on the glass substrate with the ink of an octadecylsiloxane(OTS) solution. The OTS reacted with the glass and formed a self\|assembly monolayer, and the process produced hydrophobic micro\|patterns on hydrophilic substrate. Owing to a simple hydrophobic interaction between the CuSO\-4 solution and the monolayer, a regular CuSO\-4 micro\|crystal lattice could be produced.

Facile fabrication of self-healing silicone-based poly(urea-thiourea)/tannic acid composite for anti-biofouling

A novel silicone-based poly(urea-thiourea)/tannic acid composite(PDMS-P(Ua-TUa)-TA)with excellent mechanical,self-healing and antifouling properties is developed.The multiple dynamic hydrogen bonds formed by thiourea groups,urea groups,and tannic acid(TA)molecules ensured a tough elastomer(ultimate strength:2.47 MPa)with high stretchability(~1000%).TA molecules as partial hydrogen bonding cross-linking sites interacted rapidly with urea and thiourea groups before the migration of polymer chains,resulting in fast and efficient self-healing.Scratches on the film completely disappeared within12 min,and the repair efficiency of strength was up to 98.4%within 3 h under ambient condition.Selfhealing behavior was also evaluated in artificial seawater and the healing efficiency(HE)was 95.1%.Furthermore,TA uniformly dispersed in the polymer matrix provides good antibacterial and anti-diatom properties,as well as strong adhesion to the substrate(~2.2 MPa).Laboratory bioassays against marine bacteria adhesion(~96%,~95%and~93%reduction for P.sp.,E.coli,and S.aureus,respectively)and diatom attachment(~84%reduction)demonstrated an outstanding antifouling property of the PDMSP(Ua-TUa)-TA.This work provides a promising pathway towards the development of high-performance silicone-based coatings for marine anti-biofouling.

Structured PDMS Chambers for Enhanced Human Neuronal Cell Activity on MEA Platforms

Structured poly（dimethylsiloxane） （PDMS） chambers were designed and fabricated to enhance the signaling of human Embryonic Stem Cell （hESC） - derived neuronal networks on Microelectrode Array （MEA） platforms. The structured PDMS chambers enable cell seeding on restricted areas and thus, reduce the amount of needed coating materials and cells. In addition, the neuronal cells formed spontaneously active networks faster in the structured PDMS chambers than that in control chambers. In the PDMS chambers, the neuronal networks were more active and able to develop their signaling into organized signal trains faster than control cultures. The PDMS chamber design enables much more repeatable analysis and rapid growth of functional neuronal network in vitro. Moreover, due to its easy and cheap fabrication process, new configurations can be easily fabricated based on investigator requirements.