Effects of surface-functionalized multi-walled carbon nanotubes on the properties of poly(dimethyl siloxane) nanocomposites

The effects of surface-functionalized multi-walled carbon nanotubes (MWNTs) on the properties of poly(dimethyl siloxane) (PDMS) nanocomposites are investigated in the present study. The surface functionalization of MWNTs is carried out by diphenyl-carbinol functionalization followed by reaction with multifunctional silane, 3-aminopropyltriethoxisilane. Fourier transform infrared spectroscopy (FT-IR) and energy dispersion spectroscopy (EDS) analysis are used to confirm the presence of diphenyl-carbinol and silane on the surface of the MWNTs. The effects of the MWNTs’ surface treatment on the thermal and electrical properties of poly(dimethyl siloxane)-based (PDMS) nanocomposites are also studied. The results show that the grafting of silane molecules onto diphenyl-carbinol-functionalized MWNTs (SD-MWNTs) improves the dispersion of MWNTs in PDMS; this subsequently enhances the thermal conductivity and dynamic mechanical properties as compared to those containing unmodified (U-MWNTs) and diphenyl-carbinol-functionalized MWNTs (D-MWNTs). The electrical conductivity of the nanocomposites is shown to decrease due to the wrapping of MWNTs with non-electrical-conducting organic materials.     

Blends and clay nanocomposites of cellulose acetate and poly(epichlorohydrin)

The aim of this work was to investigate cellulose acetate/poly(epichlorohydrin) (CA/PEPi) blends and cellulose acetate/poly(epichlorohydrin)/organically modified montmorillonite clay nanocomposites (CA/PEPi/MMTO) prepared by melt processing in a twin-screw extruder. The combination of an elastomer and clay in the cellulose acetate matrix was an attempt made to reach a balance between toughness and strength properties. The blend and nanocomposite structure, morphology and thermal properties were investigated by small angle X-ray scattering, transmission electron microscopy and dynamical mechanical analysis. The results showed immiscibility of the polymer components for all the CA/PEPi blend composition range investigated. In the case of the nanocomposites, the results indicated a significant polymer intercalation in the clay gallery as well as the exfoliation of the silicate layers. Moreover, the organoclay was present in the CA phase, but some of the organoclay migrated to the CA/PEPi interface and tended to surround the PEPi phase. The addition of PEPi elastomer to cellulose acetate showed a significant increase in the blend impact resistance. However the combination of PEPi and MMTO did not in fact produce a good stiffness versus toughness balance.     

Graphene foam/carbon nanotube/poly(dimethyl siloxane) composites for exceptional microwave shielding

Highly porous poly(dimethyl siloxane) (PDMS) composites containing cellular-structured microscale graphene foams (GFs) and conductive nanoscale carbon nanotubes (CNTs) are fabricated. The unique three-dimensional, multi-scale hybrid composites with inherent percolation and a high porosity of 90.8% present a remarkable electromagnetic interference shielding effectiveness (EMI SE) of ∼75 dB, a 200% enhancement against 25 dB of the composites made from GFs alone with the same graphene content and porosity. The corresponding specific EMI SE measured against the composite density is 833 dB cm³/g. These values are among the highest for all carbon filler/polymer composites reported thus far. Significant synergy arises from the hybrid reinforcement structure of the composites: the GFs drive the incident microwaves to be attenuated by dissipation of the currents induced by electromagnetic fields, while the CNTs greatly enhance the dissipation of surface currents by expanding the conductive networks and introducing numerous interfaces with the matrix.     

Patterning of TiO2 particles on poly(dimethyl siloxane) films by using proton irradiation and liquid-phase deposition process

Micropatterning of titanium dioxide (TiO2) on the surface of thin poly(dimethyl siloxane) (PDMS) films was described by means of proton irradiation and liquid-phase deposition (LPD) techniques. The surface of thin PDMS films was irradiated with accelerated proton ions through a pattern mask in the absence or presence of oxygen in order to create hydrophilically/hydrophobically patterned surfaces. The results of the surface analysis revealed that the PDMS films irradiated at the fluence of 1 x 10(15) ions cm-2 in the presence of oxygen showed the highest hydrophilicity. The LPD of TiO2 particles on the patterned PDMS film surface showed a selective deposition of TiO2 on the irradiated regions, leading to well defined TiO2 micropatterns. The crystal structure of the formed TiO2 films was found to be in an anatase phase by X-ray diffraction analysis. This process can be applied for patterning various metal and metal oxide particles on a polymer substrate.     

Sustainable production of polyurethane from castor oil,functionalized with epoxy- and hydroxyl-terminated poly(dimethyl siloxane) for biomedical applications

A sustainable method has been employed for the production of a biomedical material in an economical way. Among biomedical polymers, two mostly used polymers are silicones (PDMS) and polyurethanes (PU). PDMS can outperform other polymers due to its biocompatibility and flexibility, but its high cost became a major roadblock for many applications. PU can be produced from a variety of sustainable resources in a cost effective manner. In this work, vegetable oil-based PU is blended with PDMS to produce a biomedical material which can contribute to the economy and environment. In this method, siliconized epoxy-terminated polyurethanes (EPDMS) were prepared from castor oil, 4,4’ methylene-bis-(cyclohexyl isocyanate), glycidol, and hydroxy-terminated poly-(dimethyl siloxane) (HTPDMS). The properties of the resulting products were compared with virgin PU with a NCO/OH ratio of 1.2:1 and epoxy-terminated PU (EPU) with a polyol/diisocyanate/glycidol ratio of 1:3:3. The structural elucidation of PU, EPU, and EPDMS were carried out by FTIR and ¹HNMR spectroscopic techniques. The effect of incorporation of siloxane and glycidol on the thermal properties of PU was analyzed by thermogravimetric analysis and differential scanning calorimetry analysis. The improved hydrophobicity of the EPDMS was observed from water contact angle measurements. The surface morphology was examined using atomic force microscopy analysis. In vitro cytotoxicity analysis revealed the cytocompatibility of the EPDMS which makes them suitable for biomedical applications.     

氨基硅油改性聚丁二烯聚氨酯脲的合成与性能

过量的甲苯二异氰酸酯（TDI0加入氨乙基氨丙基聚二甲基硅氧烷（AEAPS）,端羟基聚丁二烯（HTPB）中制成预聚体,以3,3′－二氯－4,4′二苯基甲烷二胺（MOCA）为固化剂,合成了一系列不同含量的硅氧烷改性聚丁二烯聚氨酯脲,通过接触角,表面光电子能谱（ESCA）测试,应用应变,动态力学热分析,结果表明,氨基硅油在聚氨酯脲表面明显富集,聚丁二烯聚氨酯脲的力学性能改变不大。     

含亚苯基甲基苯基硅树脂的合成及表征

以甲基、苯基氯硅烷和1,4-二(羟基二甲基硅基)苯为原料,采用水解-缩聚法合成了主链含亚苯基的甲基苯基有机硅树脂,并对其结构和性能进行了研究。红外光谱(FT-IR)和核磁共振(29Si NMR)分析表明,亚苯基被成功引入到硅树脂主链中。差式量热扫描(DSC)分析表明硅树脂为均聚物。热失重(TG)结果表明,在N2氛中,硅树脂在450℃失重约1%,优于普通甲基苯基硅树脂。硅树脂的清漆涂层在300℃下使用时,附着力、抗冲击、柔韧性能仍保持良好。电化学阻抗分析(EIS)结果表明,硅树脂的清漆涂层常温固化后、经300℃的高温烘烤后都具有优良的耐腐蚀性能。     

聚甲基三氟丙基硅氧烷合成的研究进展

聚甲基三氟丙基硅氧烷(PMTFPS)可通过1,3,5-三甲基-1,3,5-三(3′,3′,3′-三氟丙基)环三硅氧烷(D3F)的阴离子开环聚合制备。归纳总结了PMTFPS合成方法的最新研究进展,主要从聚合机理、工艺条件的研究进行了总结与分析;并对合成方法目前存在的问题和发展方向进行了展望。     

Microfluidic characterization and continuous separation of cells and particles using conducting poly(dimethyl siloxane) electrode induced alternating current-dielectrophoresis

This paper presents a poly(dimethyl siloxane) (PDMS) polymer microfluidic device using alternating current (ac) dielectrophoresis (DEP) for separating live cells from interfering particles of similar sizes by their polarizabilities under continuous flow and for characterizing DEP behaviors of cells in stagnant flow. The ac-DEP force is generated by three-dimensional (3D) conducting PDMS composite electrodes fabricated on a sidewall of the device main channel. Such 3D PDMS composite electrodes are made by dispersing microsized silver (Ag) fillers into PDMS gel. The sidewall AgPDMS electrodes can generate a 3D electric field that uniformly distributes throughout the channel height and varies along the channel lateral direction, thereby producing stronger lateral DEP effects over the entire channel. This allows not only easy observation of cell/particle lateral motion but also using the lateral DEP force for manipulation of cells/particles. The former feature is used to characterize the frequency-dependent DEP behaviors of Saccharomyces cerevisiae (yeast) and Escherichia coli (bacteria). The latter is utilized for continuous separation of live yeast and bacterial cells from similar-size latex particles as well as live yeast cells from dead yeast cells. The separation efficiency of 97% is achieved in all cases. The demonstration of these functions shows promising applications of the microfluidic device.     

低交联季铵化改性氨基硅油的合成

采用四甲基氢氧化铵的硅醇盐为阴离子催化剂,以八甲基环四硅氧烷(D4)、N-(β-氨乙基)-γ-氨丙基甲基二甲氧基硅烷(KH602)和止链剂六甲基二硅氧烷(MM)为原料通过一步聚合法制备得到了具有一定黏度的氨基硅油,并通过环氧氯丙烷对双氨基硅油进行处理得到了低交联氨基硅油,后者通过环氧氯丙烷再一次处理制备得到了低交联季铵化改性氨基硅油.研究发现改性后的氨基硅油具有良好的抗黄变性能,其水溶性也得到了改善.     

Dip-pen nanolithography with poly(diallyl dimethyl ammonium) chloride

Poly(diallyl dimethyl ammonium) chloride (PDAC), a high molecular weight cationic polyelectrolyte, was used as ink for dip-pen nanolithography. Line patterns were generated on bare silicon wafers directly with PDAC-coated tips. Widths and heights of lines increased with decreasing scan rates. At the same scan rate, widths and heights of patterning decreased with increasing PDAC molecular weight. The dependence of line width on inverse writing speed was found to be consistent with a modified diffusion model.     

Radical reactions of [60]fullerene mediated by manganese(III) acetate dihydrate

Mn(OAc)3 x 2H2O is an excellent reagent to promote free radical reactions of C60. C60 reacted with various methylene active compounds, methyl ketones, beta-enamino carbonyl compounds, carboxylic acid derivatives, and diallylamines in the presence of Mn(OAc)3 x 2H2O to afford singly-bonded fullerene dimers, 1,4-bisadducts and 1,16-bisadducts of C60, C60-fused dihydrofuran derivatives, methanofullerenes, C60-fused pyrroline derivatives, C60-fused lactone derivatives, and C60-fused pyrrolidine derivatives. Mn(OAc)3 x 2H2O was successfully employed to transform ArC60-H into ArC60-OAc.     

Water-soluble binder of cellulose acetate butyrate/poly(ethylene glycol) blend for powder injection molding

A new binder system consisting of cellulose acetate butyrate (CAB) and poly(ethylene glycol) (PEG) with various molecular weights was introduced. CAB and PEGs with various molecular weights had good compatibility. The blends exhibited low enough viscosity to make homogeneous feedstock for the injection molding. Shape maintenance during the extraction by an environmentally favored solvent of water was excellent, and final sintered parts had excellent dimensional stability (±0.3%) and high sintered density over 98%. We also found that injection cycle time was comparable to that of commonly used wax-based feedstock.     

多糖介质中分散聚合法合成P(PEGDA)凝胶微球

以聚乙二醇双丙烯酸酯(PEGDA)为单体,过硫酸铵(APS)为引发剂,N,N'-亚甲基双丙烯酰胺(BIS)为交联剂,聚乙烯吡咯烷酮(PVP)为分散剂,在一定比例的壳聚糖多糖介质中,用分散聚合法制备P(PEGDA)凝胶微球.采用傅立叶红外光谱仪及扫描电镜对微球成分和形貌进行了表征,并研究了反应时间、反应温度、KCl用量和...     

Electromechanical response of a soft and flexible actuator based on polyaniline particles embedded in a cross-linked poly(dimethyl siloxane) network

Electroviscoelastic characteristics of poly (dimethyl siloxane) (PDMS) networks containing camphorsulfonic acid (CSA) — doped polyaniline (PANI) particles were investigated. Samples were prepared by dispersing fine PANI particles in a cross-linked PDMS matrix. Rheological properties of the PANI/PDMS composites were studied in oscillatory shear mode to elucidate the effects of electric field strength, particle concentration, and operating temperature on the electromechanical response. On application of an electric field the storage modulus G′ increases by an amount ▵G′ ∼ 10–50%, depending on PANI volume fraction, as the field strength is increased to 2 kV/mm. This increase in modulus is only partially reversible (about 37.5% recovery) on removal of the applied field, indicating that a quasi-permanent polarization is induced in the PANI particles. It is presumed that the increase in storage modulus originates in an electrostriction effect due to the attractive forces between polarized PANI particles embedded in the PDMS network. The temperature dependence of ▵G′ shows a maximum at T ∼ 325 °K, corresponding to the temperature range where the conductivity of PANI attains its maximum value. Finally, we report observations of the electromechanical response of a PANI/PDMS composite film, suspended in silicone oil between copper electrodes, which is manifested upon application of an electric field as a field-dependent deflection.     

Charge injection into poly[methyl(phenyl)silylene]

Space-charge-limited currents have been measured in thin films of poly[methyl(phenyl)silylene] provided with Al and hole-injecting ITO electrodes. Electroluminescence observed at high voltages was interpreted as being due to a double injection. The thermo-modulated space-charge-limited current technique has been employed to determine the structure of traps in the low-voltage (single-injection) regime.     

Separation of proteins from aqueous solution using cellulose acetate/poly (vinyl chloride) blend ultrafiltration membrane

Cellulose acetate (CA) membranes are widely used for ultrafiltration applications. CA and poly (vinyl chloride) (PVC) blend membranes are prepared by using polar solvent of N, N-dimethylformamide (DMF) by phase inversion method. Polyethylene glycol (PEG 600) is used as polymeric additive in the casting solution. The effect of polymer composition and additive concentration on surface morphology, porosity are studied. The morphology of prepared membranes is found to have asymmetric structure with dense skin layer and porous sub-layer. Applications of these membranes are carried out for rejection and permeation of macromolecular proteins such as trypsin, pepsin, egg albumin, bovine serum albumin. On increasing the concentration of PVC and PEG 600, protein rejection decreases whereas permeate flux increases.CA/PVC/PEG (70/30/10 wt%) blend membrane shows the highest permeation flux of 211.1 lm⁻² h⁻¹ for trypsin.