Ultrathin poly(N-isopropylacrylamide) grafted layer on polystyrene surfaces for cell adhesion/detachment control

We investigated physicochemical properties of two types of poly(N-isopropylacrylamide) (PIPAAm)-grafted tissue culture polystyrene (TCPS) surfaces, to elucidate the influential factors for thermally regulated cell adhesion and detachment to PIPAAm-grafted surfaces. The two types of PIPAAm-grafted surfaces were prepared by the electron beam polymerization method. Attenuated total reflection Fourier transform infrared spectroscopy revealed that amounts of the grafted polymers were 1.4 +/- 0.1 microg/cm2 for PIPAAm-1.4 and 2.9 +/- 0.1 microg/cm2 for PIPAAm-2.9. Both PIPAAm-grafted surfaces showed hydrophobic/hydrophilic property alterations in response to temperature. However, PIPAAm-1.4 surfaces were more hydrophobic (cos theta = 0.21 at 37 degrees C and cos theta = 0.35 at 20 degrees C) than PIPAAm-2.9 (cos theta = 0.42 at 37 degrees C and cos theta = 0.50 at 20 degrees C) both above and below the PIPAAm's transition temperature. Thicknesses of the grafted PIPAAm layers were estimated to be 15.5 +/- 7.2 nm for PIPAAm-1.4 and 29.5 +/- 8.4 nm for PIPAAm-2.9, by the use of UV excimer laser and atomic force microscope. Bovine carotid artery endothelial cells (ECs) adhere to the surfaces of PIPAAm-1.4 and proliferate to form confluent cell monolayers. The cell monolayers were harvested as single cell sheets by temperature decrease from 37 to 20 degrees C. On the contrary, ECs did not adhere to the surfaces of PIPAAm-2.9. This phenomenon was correlated with an adsorption of cell adhesion protein, fibronectin, onto surfaces ofPIPAAm-1.4 and -2.9. In the case of nano-ordered thin grafted surfaces, the surface chain mobility is strongly influenced by the thickness of PIPAAm grafted layers because dehydration of PIPAAm chains should be enhanced by the hydrophobic TCPS surfaces. PIPAAm graft amounts, that is, thickness of the PIPAAm grafted layers, play a crucial role in temperature-induced hydrophilic/hydrophobic property alterations and cell adhesion/detachment behavior.     

Photochemically controlled electrochemical deposition and dissolution of Ag0 nanoclusters on au electrode surfaces

A photoisomerizable thiolated nitrospiropyran SP, (1a), monolayer is assembled on a Au electrode by the primary deposition of thiolated nitromerocyanine isomer 1b as a monolayer on the electrode, followed by the irradiation of the surface with visible light, lambda > 475 nm. The surface coverage of nitrospiropyran units (1a) on the electrode is 2 x 10-10 mole cm-2. Irradiation of the electrode with UV light, 320 nm < lambda < 360 nm, results in the nitromerocyanine, MR, monolayer on the electrode that binds Ag+ ions to the phenolate units. The Ag+ ions associated with the MR monolayer undergo cyclic reduction to surface-confined Ag0 nanoclusters, and reoxidation and dissolution of the Ag0 nanoclusters to Ag+ ions associated with the monolayer are demonstrated. The electron-transfer rate constants for the reduction of Ag+ to Ag0 and for the dissolution of Ag0 were determined by chronoamperometry and correspond to ketred = 12.7 s-1 and ketox = 10.5 s-1, respectively. The nanoclustering rate was characterized by surface plasmon resonance measurements, and it proceeds on a time scale of 10 min. The size of the Ag0 nanoclusters is in the range of 2 to 20 nm. The electrochemically induced reduction of the MR-Ag+ monolayer to the MR-Ag0 surface and the reoxidation of the MR-Ag0 surface control the hydrophilic-hydrophobic properties of the surface. The advancing contact angle of the MR-Ag0-functionalized surface is 59 degrees , and the contact angle of the MR-Ag+-monolayer-functionalized surface is 74 degrees . Photoisomerization of the Ag0-MR surface to the Ag0-SP state, followed by the oxidation of the Ag0 nanoclusters, results in the dissolution of the Ag+ ions into the electrolyte solution.     

Magnetic field assisting DC electrodeposition: general methods for high-performance Ni nanowire array fabrication

One-dimensional magnetic nanowires are generally thought to show fine axial magnetism for their special high aspect ratio of the shape. However, the magnetic nanowire arrays fabricated by DC electrodeposition in template pores always show a low squareness in parallel to the nanowire direction. We developed two general and simple methods to improve the squareness of the as-fabricated Ni nanowire arrays parallel to the nanowire direction. The nanowires are found to be polycrystalline. The magnetism of the nanowire is also analyzed based on the microstructure.     

Pinning of single-walled carbon nanotubes by selective electrodeposition

A maskless method for the fabrication of electrical or mechanical contacts to the single-walled carbon nanotubes (SWNTs) by selective electrodeposition is reported. Both semiconducting SWNTs and metallic SWNTs can be pinned on prepatterned electrodes by the locally deposited metal, leaving the section of SWNTs between the electrodes clean. The distribution of deposited metal on the SWNTs is mainly determined by the covering power of the plating bath and the plating potential. This research provides a parallel method for the large-scale integration of SWNTs into electronic, optoelectronic, and sensing systems.     

Chitosan-mediated and spatially selective electrodeposition of nanoscale particles

Nanoscale particles offer a variety of interesting properties, and there is growing interest in their assembly into higher ordered structures. We report that the pH-responsive aminopolysaccharide chitosan can mediate the electrodeposition of model nanoparticles. Chitosan is known to electrodeposit at the cathode surface in response to a high localized pH. To demonstrate that chitosan can mediate nanoparticle deposition, we suspended fluorescently labeled latex nanoparticles (100 nm diameter spheres) in a chitosan solution (1%) and performed electrodeposition (0.05 mA/cm2 for several minutes). Results demonstrate that chitosan is required for nanoparticle electrodeposition; chitosan confers spatial selectivity to electrodeposition; and nanoparticles distribute throughout the electrodeposited chitosan film. Additionally, we observed that the deposited films reversibly swell upon rehydration. This work indicates that chitosan provides a simple means to assemble nanoparticles at addressable locations and provides further evidence that stimuli-responsive biological materials may facilitate fabrication at the microscale.     

Chitosan biotinylation and electrodeposition for selective protein assembly

An alternative route to protein assembly at surfaces based on using the unique capabilities of biological materials for the spatially selective assembly of proteins is described. Specifically, the stimuli-responsive properties of aminopolysaccharide chitosan are combined with the molecular-recognition capabilities of biotin-streptavidin binding. Biotinylated chitosan retains its stimuli-responsive properties and is capable of electrodepositing at specific electrode addresses. Once deposited, it is capable of binding streptavidin, which can mediate the subsequent assembly of biotinylated proteins. Spatially selective protein assembly using biotinylated Protein A and fluorescently-labeled antibodies is demonstrated.     

Preparation of thermoplastic elastomer from natural rubber grafted with polystyrene

Thermoplastic elastomer was prepared from deproteinized natural rubber (DPNR) by graft-copolymerization of styrene, which was performed onto rubber particles of about 1 μm in diameter in latex stage with tert-butyl hydroperoxide/tetraethylenepentamine as an initiator. Suitable initiator concentrations were determined to be 3.3 × 10⁻² and 20 × 10⁻² mol/kg-rubber for the graft-coplymerization of styrene of 1.5 and 5.5 mol/kg-rubber, respectively, in which conversion and grafting efficiency of styrene were more than 90 mol% and 80 mol%, respectively. The resulting polystyrene, grafted onto the rubber particles, was characterized by size exclusion chromatography after ozonolysis. Morphology of the DPNR grafted with polystyrene (DPNR-graft-PS) was observed by transmission electron microscopy (TEM). Change in morphology after processing the DPNR-graft-PS at 150 °C was associated with change in mechanical properties, i.e. stress at strain of 1 and stress at break. The outstanding mechanical properties, maintained even after processing, were assigned to the thermoplasticity of the DPNR-graft-PS, based on the high conversion and high grafting efficiency.     

Radiation effect on polystyrene deposited and grafted on silica gel

The effect of radiation on polystyrene was studied in the presence and absence of silica gel by molecular weight measurement with GPC. Polystyrene crosslinked under vacuum in the absence of silica gel, but it either crosslinked or degraded by radiation, depending on the molecular weight of the polymer in the presence of silica gel. Part of the deposited polymer bonded to silica gel by radiation; the G value for graft-chain formation is in the range of 0.01–0.1. Irradiation of polystyrene grafted on silica gel resulted in degradation of the graft chain because of the transfer of energy from silica gel. The G value for main chain scission was about 2 when graft polymer was irradiated in the absence of homopolymer. The degradation of graft polymer was suppressed when the polymer was irradiated in the presence of homopolymer, and the amount of unextractable polymer from silica gel increased with increasing irradiation. This adds evidence to the estimation that an increase in grafting percent coupled with a slight decrease in molecular weight at a later stage of radiation-induced polymerization of styrene adsorbed on silica gel is due to a secondary effect of radiation on the polymer.     

聚N-异丙基丙烯酰胺接枝聚苯乙烯高分子刷的构象

当长链高分子高密度接枝到一个表面上时,由于分子链间的相互作用使得接枝的高分子链扩张而形成伸直链的构象,这种形态被称为高分子刷.     

Increasing selective bilirubin removal by hypercross-linked polystyrene hemosorbents

A high efficiency of indirect bilirubin removal from systems modelling blood plasma by polymers of various structures and, most importantly, by hemocompatible hypercross-linked polystyrenes such as Styrosorb is demonstrated. Approaches to increasing the selectivity of hypercross-linked polystyrenes for the removal of bilirubin from biological fluids with a high serum albumin content were found, making them promising materials for the manufacture of hemosorption columns effective for hepatitis therapy and other conditions caused by a high bilirubin content in the blood plasma.     

Microporous polystyrene particles for selective carbon dioxide capture

This study presents the synthesis of microporous polystyrene particles and the potential use of these materials in CO(2) capture for biogas purification. Highly cross-linked polystyrene particles are synthesized by the emulsion copolymerization of styrene (St) and divinylbenzene (DVB) in water. The cross-link density of the polymer is varied by altering the St/DVB molar ratio. The size and the morphology of the particles are characterized by scanning and transmission electron microscopy. Following supercritical point drying with carbon dioxide or lyophilization from benzene, the polystyrene nanoparticles exhibit a significant surface area and permanent microporosity. The dried particles comprising 35 mol % St and 65 mol % DVB possess the largest surface area, ～205 m(2)/g measured by Brunauer-Emmett-Teller and ～185 m(2)/g measured by the Dubinin-Radushkevich method, and a total pore volume of 1.10 cm(3)/g. Low pressure measurements suggest that the microporous polystyrene particles exhibit a good separation performance of CO(2) over CH(4), with separation factors in the range of ～7-13 (268 K, CO(2)/CH(4) = 5/95 gas mixture), which renders them attractive candidates for use in gas separation processes.     

Synthesis and characterization of styrene grafted carbon nanotube and its polystyrene nanocomposite

Effective side wall functionalization of single-walled carbon nanotube (SWCNT) with 4-vinylaniline was carried out through solvent free functionalization. The functionalized SWCNT was characterized through FT-IR and NMR. Typical peaks to identify the functionalization were observed. Thermal analysis shows around 48% weight loss in functionalized SWCNT in comparison to the pure SWCNT. The ratio of disordered to order transition (I_D/I_G) in FT-Raman, indicated the generation of some surface defects due to functionalization. Near infrared spectrum of functionalized SWCNT also confirmed the functionalization of SWCNT. The polystyrene nanocomposite materials were prepared with functionalized SWCNT as fillers by solution casting from tetrahydrofuran. The functionalized SWCNT nanocomposite showed significant improvement in mechanical properties and electrical properties. The dispersibility of the carbon nanotube in the composite was investigated by using scanning electron microscopy.     

通过原子转移自由基聚合合成可光交联的聚苯乙烯接枝共聚物

聚苯乙烯(PS)在氯化锌(ZnCl_2)做催化剂下,通过氯甲基甲基醚氯甲基化反应,合成了氯甲基化聚苯乙烯(CMPS).在氯化亚铜/联二吡啶(CuCl/bpy)催化下,以CMPS为大分子引发剂引发甲基丙烯酸甲酯(MMA)、甲基丙烯酸酯化查尔酮(MSPK)进行原子转移自由基聚合,成功合成了侧链含有查尔酮结构的光敏聚苯乙烯接枝共聚物(PSMM),所得聚合物结构经过红外光谱(FT-IR)、核磁共振氢谱(~1H NMR)得到确认,通过热重分析(TG)、示差扫描量热法(DSC)测试了该聚合物的热学性能.结果表明,该接枝共聚物具有较好的热学性能及良好的光敏性.     

Sulfonated polystyrene grafted polypropylene composite electrolyte membranes for direct methanol fuel cells

Polypropylene (PP)-g-sulfonated polystyrene (SPS) composite membranes were prepared by grafting polystyrene (PS) on microporous polypropylene membranes via plasma-induced polymerization. Grafting of polystyrene was established not only inside the pores but also on the surface of PP membranes, followed by the sulfonation reaction. The chemical and physical structure of PS-g-PP membranes was investigated using FTIR and SEM. The thickness and weight of the composite membrane increased with increasing grafting time. Ion exchange capacity (IEC), ion conductivity, and methanol permeability coefficient were measured and analyzed according to grafting reaction and sulfonation time. While both the ion conductivity and methanol permeability coefficient increased with grafting amount, the characteristic factor was comparable to that of Nafion^®.     

Structural investigation of polystyrene grafted and sulfonated poly(tetrafluoroethylene) membranes

Structural investigation of polystyrene grafted and sulfonated poly(tetrafluoroethylene) (PTFE) membranes prepared by radiation-induced grafting of styrene onto commercial PTFE films and subsequent sulfonation was carried out by differential scanning calorimetry and X-ray diffraction. The effect of the structural changes taking place in the membranes during the preparation procedure (grafting and sulfonation) and the variation of the degree of grafting on melting temperature (T_m), glass transition temperature (T_g), heat of melting (ΔH_m), and degree of crystallinity was studied. The melting temperature (T_m) was found to be independent of the degree of grafting unlike glass transition temperature (T_g), which was found to be a function of the degree of grafting. Moreover, the degree of crystallinity of the membranes was found to decrease with the increase in the degree of grafting. The results of this work suggest that grafting takes place in the entire amorphous region without any significant disruption in the crystalline structure of PTFE film and the decrease in the degree of crystallinity is mainly attributed to the dilution effect.     

Nanotube brushes: polystyrene grafted covalently on CNx nanotubes by nitroxide-mediated radical polymerization

Polymer brushes consisting of polystyrene (PS) chains bonded covalently to N-doped multiwalled carbon nanotubes (CNx) were synthesized by a "grafting from" route using nitroxide mediated radical polymerization (NMRP).     

Organotin catalysts grafted onto cross‐linked polystyrene supports through polar spacers

The present study investigates the suitability of a HypoGel support bearing oligomeric poly(ethylene glycol) (PEG) chains to act as an insoluble carrier for grafted organotin catalysts. Through the introduction of polar spacers, an improved swelling and site accessibility in the polar media typically involved in transesterification reactions are targeted. Advanced structural investigation shows that quantitative conversion into the targeted HypoGel‐supported organotin trichloride is hampered by the existence of intra‐ and/or intermolecular donor‐acceptor O→Sn interactions caused by the presence of donor moieties in the PEG‐linker. Support is provided to the proposal that the latter interactions are at the origin of the moderate catalytic performance displayed by these HypoGel‐supported catalysts, achieving only 41% conversion after 2 hours in the transesterification of ethyl acetate and n‐octanol. In contrast with similar organotin catalysts supported by an alkyl spacer, the HypoGel‐supported materials appear to be poorly recyclable and display poor leaching resistance. Copyright © 2009 John Wiley & Sons, Ltd.     

Self-assembled electrodes based on polyaniline grafted with reduced graphene oxide and polystyrene sulfonate

Journal of Solid State Electrochemistry - In this work, composites based on polyaniline (PAni) grafted with reduced graphene oxide (rGO) were obtained by the in situ chemical polymerization of...     

Thickness of the soft layer on glassy polystyrene surfaces

The flow behavior of the near-surface region of polystyrene films was studied via the decay kinetics of imprinted corrugation gratings at elevated temperatures. The speed of the decay is the result of a balance between surface tension, on the one hand, and viscous drag, on the other. Depth profiling is possible because the penetration depth of a surface wave is proportional to its wavelength. From the dependence of the decay rate on the penetration depth one concludes that the surface region displays an increased molecular mobility. The soft surface layer has a thickness of about 20 nm. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3031–3036, 2006