Polyacrylonitrile silica

Wang N, Si Y, Wang N, Sun G, El-Newehy M, Al-Deyab SS, Ding B (2014) Multilevel structured polyacrylonitrile/silica nanofibrous membranes for high-performance air filtration. Separation Purification Technol 126 44—51... 

Ji L and Zhang X (2008) Ultrafine polyacrylonitrile/silica composite fibers via electrospinning. 

The hybrid nanocomposite polymer-silica materials on the basis of oligomer alkoxysilane (polyethoxysilane (PES) obtained from tetraethoxysilane) with polycaproamide, polyacrylonitrile, chitosan and zirconyl oxychloride were investigated. 

Select mobile phases for HPSEC based on their ability to dissolve the sample and their compatibility with the column. Zorbax PSM columns are compatible with a wide variety of organic and aqueous mobile phases (Table 3.4), but analysts should avoid aqueous mobile phases with a pH greater than 8.5. As mentioned earlier, select mobile phases that minimize adsorption between samples and silica-based packings. Sample elution from the column after the permeation volume indicates that adsorption has occurred. If adsorption is observed or suspected, select a mobile phase that will be more strongly adsorbed onto the silica surface than the sample. For example, N,N-dimethyl-formamide (DMF) is often used for polyurethanes and polyacrylonitrile because it eliminates adsorption and dissolves the polymers. When aqueous mobile phases are required, highly polar macromolecules such as Carbowax can be used to coat the silica surface and eliminate adsorption. Table 3.5 provides a list of recommended mobile-phase conditions for some common polymers. 

Oxide-water interfaces, in silica polymer-metal ion solutions, 22 460—461 Oxidimetric method, 25 145 Oxidization devices, 10 77-96 catalytic oxidization, 10 78—96 thermal oxidation, 20 77-78 Oxidized mercury, 23 181 Oxidized polyacrylonitrile fiber (OPF), 23 384... 

Silica-supported cyclized polyacrylonitrile (PAN) metal complexes, claimed to be better oxidation catalysts than the polyphthalocyanine-metal complexes, have been obtained shown below as [11] ... 

Silica gel-supported, cyclized polyacrylonitrile metal complexes as well as PMAA-Pd and PMAA-Pt complexes were prepared by copolymerization of MAA and a mixture of m- and p-DVB in the presence of silica gel [131]. The catalytic activity of the obtained complexes was examined in the reaction of cumene and ethylbenzene hydrogenation [131] and in the hydrogenation of aromatic and aliphatic nitrocompounds, alkenes and aliphatic aldehydes. Based on the decrease in the bond energy of Cu2p3/2 from 935 to 932.4 eV and the increase in the bond energy of Ajs from 399 to 399.6 eV, it was found, by XPS, that Cu is bound to a complex through a nitrogen atom of PAN. 

Porous membranes can be made of polymers (polysulfones, polyacrylonitrile, polypropylene, silicones, perfluoropolymers, polyimides, polyamides, etc.), ceramics (alumina, silica, titania, zirconia, zeolites, etc.) or microporous carbons. Dense organic membranes are commonly used for molecular-scale separations involving gas and vapor mixtures, whereas the mean pore sizes of porous membranes is chosen considering the size of the species to be separated. Current membrane processes include microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), gas and vapor separation (GS), and pervaporation (PV). Figure 1 indicates the types and sizes of species typically separated by these different separation processes. 

Making use of constrained polymerisation of divinylbenzene on surfactant-modified colloid silica, Jang and Lim prepared carbon nanocapsules and mesocellular foams. Later, they reported that mesoporous carbons with highly uniform and tunable mesopores were fabricated by one-step vapour deposition polymerisation using colloidal silica nanoparticles as template and polyacrylonitrile as carbon precursor. Hampsey et al. recently reported the synthesis of spherical mesoporous carbons via an aerosol-based, one-step approach using colloidal silica particles and/or silicate clusters as template. ... 

Fig. 10 TEM images (scale bars. 100 nm) of (a) PMMA latex armored with Ludox silica nanoparticles. Multilayered nanocomposite polymer colloids with (b) a hairy outer layer of polyacrylonitrile, and (c) a soft shell of poly(n-butyl acrylate). Reproduced from [66] with permission of American Chemical Society...

Freshly distilled 4-VP was mixed with dihaUdes (molar ratio 2 1) in bulk or in solution. The polymerization proceeded to virtual completion in bulk or in solvents (benzene, methanol, dimethylformamide (DMF) or mixtures of DMF with methanol) and in presence of e.g., silica gel, carbon black, sand, porous materials, e.g., paper, cloth, polyacrylonitrile fibers, etc. The rate of polymerization was significantly enhanced in absence of air or by COy irradiation. The mixtures of 4-VP and dihalides were left at room temperature for periods of 5 days during which time the color changed from colorless to pink or red. The resin was isolated by addition of acetone and washing with acetone. After drying it was obtained in the form of a light yellow powder in yields of 70 to 100% of the theoretical amount. 

Loger et al. (24,25) chromatographed 19 basic dyes for polyacrylonitrile fibers on alumina with ethanol-water (5 2) and another 11 dyes on silica gel G with pyridine-water (1 2) as the solvent system. Arsov et al. (26) chromatographed 23 basic dyes on silica gel with various solvents. Takeshita et al. 

Thirteen dyes were separated by reversed phase TLC on C g modified silica gel using methanol-acetonitrile-aq. 5% Na2S04 (3 3 10) and then methanol-ethylmethyl ketone-aq. 5% Na2 SO4 (1 1 1) as mobile phases in same direction. Separation was optimum between pH 6.0 to 7.0 (145). Four basic dyes were separated on pretreated silica gel plates using HCIO4 or benzene sulphonic acid as counter ion and aqueous 50% or 60% ethanol as mobile phase (146). Polyacrylonitrile plates have been used for the separation of ten basic and common food dyes along with other dyes using diethylamine-anhy. acetic acid-H20 (4 1 15) as mobile phase (147). 

In a way similar to PDMS and TEOS, other organic polymers have been functionaliz with alkoxysilyl groups and covalently bonded to silica. Polymers that have been coupled with silica are PTMO-based polyurethane oligomers T69 polyoxazolines , polyimide, poly(arylene ether ketone) poly(arylene ether sulfone), polystyrene polyoxopropylene (PPO) ", polyacrylonitrile, copolymers of methyl methacrylate and allyl methacrylate and cyclophosphazenes. ... 

The ATRP fabrication of polyacrylonitrile (PAN), poly (2-(dimethyl-amino)ethyl methacrylate), and polystyrene end-grafted chains on the inner walls of ordered mesoporous silica [31]... 

Yu T, Lin J, Xu J, Chen T, Lin S and Tian X (2007) Novel polyacrylonitrile/Na-MMT/silica nanocomposite Co-incorporation of two different form iiauo materials into polymer matrix. Compos Sd Technol 67 3219-3225. 

Membranes with pores having pore diameters in the nanometer range ean be obtained by pyrolysis. Molecular sieves can be prepared by controlled pyrolysis of thermoset polymers [poly(vinylidene chloride), poly(furfuryl alcohol), cellulose, cellulose triacetate, polyacrylonitrile (PAN), and phenol formaldehyde] to obtain carbon membranes, or of silicone rubbers to obtain silica filters. For example, carbon molecular sieves can be obtained by pyrolysis of PAN hollow fibers in an inert atmosphere, which leads to dense membranes whose pores are opened by oxidation, initially at 400°-500°C and finished at 700°C [15]. These membranes are used to separate O2 /N2 mixtures. Le Carbone-Lorraine deposits a resin into a tubular macroporous substrate and then by pyrolysis creates a thin (< 1 pm) carbon active layer. Silicon rubber tubes can be pyrolyzed in an inert atmosphere at temperatures around 700°C followed by oxidation in air at temperatures from 500° to 900°C [16]. The membranes are composed almost completely of Si02 with pores having a maximum porosity of 50% and diameters fi om 5 to 10 nm. The permeabilities for He, H2, O2, and Ar range from 0.5 to 5 x 10 m s Pa. 

Jung H-R, Ju D-H, Lee W-J, Zhang X, Kotek R (2009) Electrospun hydrophilic fumed silica/polyacrylonitrile nanofiber-based composite electrolyte membranes. Electrochim Acta 54(13) 3630-3637. doi 10.1016/j.electacta.2009.01.039... 

---