Radiation grafted poly(vinylidene fluoride)-graft-polystyrene sulfonic acid membranes for fuel cells: Structure-property relationships

<正>Structure-property relationships for poly(vinylidene fluoride)-graft-polystyrene sulfonic acid(PVDF-g-PSSA) fuel cell membranes prepared by a single step method involving radiation-induced grafting of sodium styrene sulfonate(SSS) onto electron beam(EB) irradiated poly(vinylidene fluoride)(PVDF) films were established.The physico-chemical properties of the membranes such as ion exchange capacity,water swelling and proton conductivity were correlated with the degree of grafting(G,%) and the structural changes taking place in the membrane matrix during the preparation procedure. The variation in the crystallinity and the thermal stability of membranes was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis(TGA),respectively.The membranes were found to undergo substantial structural changes in forms of ionic sites increase,hydrophilicity enhancement,hydrophobicity reduction and crystallinity decrease with the variation in G(%) and the preparation method.The structural and thermal properties of the obtained membranes were also compared with their counterparts prepared by a conventional two-steps method i.e.radiation induced grafting of styrene onto EB irradiated PVDF films followed by sulfonation.The PVDF-g-PSSA membranes obtained by a single-step method were found to have superior properties compared to those obtained by the conventional two-steps method.     

Characterization and Catalytic Activity of Titanium－containing Aluminum Phosphate Prepared by Sol－gel and Nonuniform Precipitation for O－Alkylation of Catechol with Ethanol

Three titanium-containing aluminum phosphate catalysts with a general formula A10.77Ti0.23PO4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at roomtemperature (APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N2 temperature, XRD, UV-Vis, NH3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Bronsted acid sites were more effectivo tive for the reaction.     

Surface Modification of Nano－SiO2 by Grafting PMMA／PBA

The surface of nano-SiO2 was modified by being encapsulated with hydroxy-propyl-methyl cellulose (HPMC), and then co-grafted with acrylates. The grafting conditions, such as pH of the medium, and initiator concentration have been studied. The modified nano-SiO2 particles were characterized by TEM, DSC and FT-IR spectra. TEM images show that the surface of the nano-particles has been successfully modified by a thick layer of film-like polymer in this way. The DSC results show that the decomposition temperature of modified nano-particles of SIO2 is 90 ℃ higher than that of grafted-on polymer. According to the FT-IR spectra, It is convinced that poly-methyl methacrylate ( PMMA ) and poly-acrylic butyl-ester ( PBA ) were co-grafted onto the surface of nano-SiO2.     

PREPARATION OF POLY（METHYL METHACRYLATE）/LAYERED DOUBLE HYDROXIDES NANOCOMPOSITES via in situ SOLUTION POLYMERIZATION

An exfoliated layered double hydroxides/poly(methyl methacrylate)(LDHs/PMMA)nanocomposite was prepared by in situ solution polymerization of methyl methacrylate(MMA)in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs).MgAl-VBS LDHs was prepared by the ion exchange method,and the structure and composition of the MgA1-VBS LDHs were determined by X-ray diffraction(XRD),infrared spectroscopy and elemental analysis.XRD and transmission electron microscopy(TEM)were employed to examine the structure of LDHs/PMMA nanocomposite.It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix.The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased.     

GRAFTING ONTO WOOL V.RADIATION-INITIATED GRAFTING OF ACRYLIC ACID ONTO WOOL FIBER

This paper deals with graft copolymerization of acrylic acid (AA) onto Xinjiang fine wool.fiber in aqueous medium initiated by gamma rays. Graft copolymerization was carried out by themutual irradiation method in limited air. Percent grafting and percent efficiency have been deter-mined as a function of total dose, dose rate, concentration of monomer, wool weight and reactiontemperature. Graft copolymers are characterized with infrared (IR) spectroscopy, scanning elec-tron microscopy (SEM), and X--ray diffractometer. Properties of the grafts were studied, and compared with the virgin fiber.     

Enantiomer Separation of α—Dimethyl Dicarboxylate Biphenyl and Related Biphenyl Compounds by Normal Phase HPLC on Polysaccharide Based Chiral Stationary Phases

Cellulose tris(4-methylphenylcarbamate),amylose tris(3,5-dimethylphenylcarbamate) and amylose tris (phenylcarbamate) were prepared by the method reported by Okamoto and were coated onto an aminopropylated mesoporous spherical silica gel.These final products were used as chiral stationary phases of high performance liquid chromatography for the eighteen structurally related biphenyl compounds.The resolution was made using normal-phase methodology with a mobile phase consisting of n-hexane-alcohol(ethanol,1-propanol,2-propanol or 1-butanol).The effects of various aliphatic alcohols in the mobile phase were studied.The structural features of the solutes that influence their k′ were discussed.A dominant effects of trifluoroacetic acid on chiral separation of acidic solutes was noted.     

Preparation of single-hole hollow polymer nanospheres by raspberry-like template method

Single-hole hollow polymer nanospheres were fabricated by raspberry-like template method using "graft-from" strategy through atom transfer radical polymerization (ATRP). Nanometer-sized silica spheres were covalently attached onto the surfaces of micrometer-sized silica spheres. Crosslinked polymer shells on the nano-sized spheres outside the attached area were formed by "graft-from" strategy through ATRP. After removal of the silica cores, single-hole hollow crosslinked polymer nanospheres were obtained. In this strategy, most of ATRP monomers may be used and thus many functional groups can be easily incorporated into the single-hole hollow crosslinked polymer nanospheres.     

Nanomechanical properties of polyaniline and azo polyelectrolyte multilayer films

<正>Nanomechanical properties of multilayer films constructed of polyaniline(PANI) and azobeneze-containing polyelectrolytes(PNACN and PPAPE) were studied by using nanoindentation method.The multilayer films were prepared by the electrostatic layer-by-layer self-assembly through alternately dipping in the polymer solutions.The multilayer films deposited onto the glass slides after proper dry were used for the nanomechanical property testing.The nanomechanical measurement indicated that the PANI/PNACN and PANI/PPAPE multilayers possessed the mean elastic modulus of 5.42 GPa and 4.35 GPa,and hardness of 0.26 GPa and 0.18 GPa,respectively.The nanoscratch properties of the PANI/PNACN and PANI/PPAPE multilayer films were also measured.The critical loads of PANI/PNACN and PANI/PPAPE films were 103.52 mN and 100.59 mN.The degree of electrostatic cross-linking in the multilayers could be altered by exposing the films to aqueous solutions with different pH values.As a result,the modulus and hardness of the multilayer films were changed through the solvent treatment.Both modulus and hardness of the PANI/PNACN films obviously increased after dipping the multilayer films in solutions with pH in a range from 9 to 11.     

Fabrication of Layer-by-layer Films of Polyhedral Oligomeric Silsesquioxanes

Layer-by-layer(LBL)self-assembly method was used to fabricate siliceous ultrathin films by using polyhedral oligomeric silsesquioxanes as building blocks.Ammonium salt of kctasilsesquioxane acid (OSi8) and bply(diallyldimethylammonium chloride)(PDDA) were altermately assembled onto CaF2 slide to form nanocomposite multilqyers,Linear build-up of the LBL films was confirmed by UV-Vis spectroscopy.IR spectrum suggests existence of OSi8 and PDDA in the LBL films.Atomic force microscopic surface topography of the LBL films indicates the OSi8 covers the entire surface of the topmost layer and shows a granular morphology.     

Preparation and Characterization of Nano-Structured SiO2 Thin Films on Carbon Steel

Nano-structured SiO2 thin films were prepared on the surface of carbon steel for the first time by LPD. The compositions of the films were analyzed by XPS, and the surface morphology of the thin films were observed by AFM. The thin films were constituted by compact particles of SiO2, and there was no Fe in the films. In the process of film forming, the SiO2 colloid particles were deposited or absorbed directly onto the surface of carbon steel substrates that were activated by acid solution containing inhibitor, and corrosion of the substrates was avoided. The nano-structured SiO2 thin films that were prepared had excellent protective efficiency to the carbon.     

壳聚糖-对羟基苯甲酸酶法接枝及表征

从土豆中提取酪氨酸酶(tyr),以该酶催化氧化对羟基苯甲酸(BA)成活性邻醌,成功地实现了壳聚糖(Cs)上的接枝。通过UV-Vis、FTIR、TG-SDTA对其反应产物进行结构和性能的初步表征,由线性电位滴定法测得其接枝率为47%~58%。     

磷酸可待因在安伯来特IRP-69上的离子交换平衡特性研究

采用批式离子交换法研究了磷酸可待因在安伯来特IRP-69上的离子交换平衡特性、动力学及热力学特征.结果表明,在3个温度(298K、308K和318K)及研究的浓度范围内,离子交换吸附等温方程和Freundlich方程都能够对磷酸可待因在安伯来特IRP-69上的离子交换平衡等温线进行很好的拟合,其离子交换动力学特征基本符合二级动力学方程.磷酸可待因在安伯来特IRP-69上的离子交换行为的热力学参数(ΔH、ΔG、ΔS)都小于0.在3个温度(298K、308K和318K)下,同一初始浓度(350mmol/L)的磷酸可待因在安伯来特IRP-69上的平衡交换吸附量分别为1.1295mmol/g、1.1203 mmol/g和1.1129 mmol/g.     

Directed assembly of Au nanoparticles onto planar surfaces via multiple hydrogen bonds

We have developed a new concept to effect nanoparticle binding on surfaces by use of directed, specific molecular interactions. Hamilton-type receptors displaying a binding strength of approximately 10(5) M(-)(1) were covalently fixed onto self-assembled monolayers via Sharpless-type "click" reactions, thus representing an efficient method to control the densities of ligands over a range from low to complete surface coverage. Au nanoparticles covered with the matching barbituric acid receptors bound with high selectivity onto this surface by a self-assembly process mediated by multiple hydrogen bonds. The binding process was investigated with atomic force microscopy. Moderate control of particle density was achieved by controlling the receptor density on the self-assembled monolayer surface. The method opens a general approach to nanoparticle and small object binding onto patterned surfaces.     

Graft copolymers containing nucleic acid bases and L-α-amino acids

Graft copolymers of nucleic acid bases and L-α-amino acids on polyethyleneimine were synthesized, and carboxyl derivatives of adenine and thymine were grafted by the p-nitrophenyl ester method onto linear and branched polyethyleneimine. The carboxyl derivatives of nucleic acid bases were also grafted onto the monomeric graft copolymers of L -α-amino acids on polyethyleneimine; the carboxyl derivatives were obtained by the condensation of polyethyleneimine with L -α-amino acids with a coupling agent.     

Writing with DNA and protein using a nanopipet for controlled delivery

We present a new, general method for the controlled deposition of biological molecules on surfaces, based on a nanopipet operating in ionic solution. The potential applied to the pipet tip controls the flux of biological molecules from the pipet, allowing fine control of the delivery rate. We used the ion current to control the distance of the pipet from the surface of a glass slide and deposited the fluorescently labeled DNA or protein G at a defined location onto the surface. Features of 830 nm size were obtained by depositing the biotinylated DNA onto a streptavidin surface; 1.3 mum size spots were obtained by depositing protein G onto a positively charged glass surface.     

复合型多糖类手性固定相的制备及其手性识别能力

将纤维素三(3,5-二甲基苯基氨基甲酸酯)(cellulose tris(3,5-dimethyIphenylcarbamate),CDMPC)和淀粉三(3,5-二甲基苯基氨基甲酸酯)(Amylose tris(3,5-dimethylphenylcarbamate),ADMPC)分别涂敷于氨丙基硅胶上然后混合,或者将...     

Radiation induces grafting of styrene onto silicone sealant films

Grafting of styrene onto silicone sealant films was realized in different methanol solutions by gamma radiation, from a ⁶⁰Co source at room temperature. The styrene grafted onto silicone sealant films was synthesized by pre-irradiation oxidative method. Pre-irradiation method was optimized by tuning the γ-irradiation dose, reaction time, temperature, and monomer concentration. The characterization of silicone sealant films were examined by infrared, differential scanning calorimetry, and swelling behavior analysis. The silicone sealant films could be applied to radiation resistance materials or in separation process of low volatile organic compounds from aqueous solution.     

Radical Graft Polymerization of Vinyl Monomers Initiated by A20 Groups Introduced Onto a Carbon Black Surface: Effect of azo Groups on Graft Polymerization

The radical graft polymerization of vinyl monomers from carbon black initiated by azo groups introduced onto the surface was investigated. The introduction of azo groups onto carbon black surface was achieved by three methods: the reaction of 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (AIP) with (1) epoxide groups, which were introduced by the reaction of carbon black with chlorometh-yloxirane; (2) acyl chloride groups, which were introduced by the reaction of carboxyl groups on the surface with thionyl chloride; and (3) 3-chloroformyl-1-cyano-1-methylpropyl groups, which were introduced by the reaction of carbon black with 4,4′-azobis(4-cyanovaleric acid) and then thionyl chloride. The amount of azo groups introduced onto the surface by the above methods was determined to be 0.07-0.19 mmol/g. The graft polymerization of methyl methacrylate was found to be initiated by azo groups introduced onto the carbon black surface. During the polymerization, poly(methyl methacrylate) was effectively grafted onto carbon black through propagation of the polymer from the radical produced on the surface by the decomposition of the azo groups. The percentage of grafting using carbon black having azo groups introduced by method 1 increased to 40%. It was also found that the graft polymerization of several vinyl monomers such as styrene, acrylonitrile, and acrylic acid was initiated by the azo groups introduced onto the surface and the corresponding polymer was effectively grafted onto the surface. Furthermore, the effect of the amount of carbon black having azo groups on the graft polymerization was investigated.     

Immunosensing based on site-directed immobilization of antibody fragments and polymers that reduce nonspecific binding

Antibody Fab'-fragments can be directly coupled onto gold, and the space between the fragments can be filled with protein repellent disulfide bearing polymers. Coupling of the antibody Fab'-fragments, and thus both the amount of nonspecific binding and antigen binding but also the ability to regenerate the layer, is dependent on the immobilization procedure. First, the immobilization has taken place by coupling the Fab'-fragments to the surface and thereafter attaching the polymer in the remaining space between the antibodies. Second, the Fab'-fragments have been added after the surface has been coated by polymer. Third, the Fab'-fragments and polymer have been added onto the surface from the same solution. Up to 80% of the antigen could be removed during regeneration, if proper concentrations of polymer and Fab'-fragments were immobilized onto the gold surface. Only about 60% of the antigen could be removed, when the fragments were coupled directly onto a clean Au surface before the polymer or if low concentrations of polymer were attached onto gold before the Fab'-fragments. The first immobilization method, however, showed the highest response to antigen.     

Screening for inhibitors of histone deacetylase by incorporating a spraying method to micro-arrayed compound screening

We have developed a method of spraying assay reagents onto a target gel in the Micro-Arrayed Compound Screening ( micro ARCS) format. After application of target gels to compound sheets, subsequent reagents can be applied by spraying onto the target gel. The spraying method conserves on assay reagents by up to 10-fold, eliminates the need for casting additional agarose gels, and increases the throughput of a screen by 3-fold. To demonstrate the efficacy of applying the spraying method to micro ARCS, we screened over 600,000 compounds for inhibitors of histone deacetylase (HDAC). Commercially available HDAC substrate and reaction developer were sprayed directly onto the gel to initiate the reaction and to amplify the signal, respectively. Picks in the primary screen were retested at a density of 384 compounds per sheet in the micro ARCS format. IC(50) values for active compounds were confirmed in a 96-well plate assay. The screen identified several small molecule inhibitors of the enzyme, including members of several classes of known HDAC inhibitors. The combination of the high-density format of micro ARCS, the efficiency of the spraying method, and a timed sequence of adding assay reagents permitted a screening throughput of 200,000 tests an hour. We present the details of the screening format and the analysis of the hits from the screen.