Styrene-methyl methacrylate silica

Hamann et al. (11) have prepared phenylazo-bound silica via four-step reactions from the starting silica (Aerosil 200) and carried out the polymerizations of styrene, methyl methacrylate, acrylamide, acrylonitrile, acrylic acid, and 4-vinylpyri-... 

As it was mentioned above, olefin groups attached to silica surface under conditions of 7-irradiation or in the presence of benzoyl peroxide enter into the reaction of copolymerization with unsaturated acids, styrene, methyl methacrylate, acrylonitrile, and other compounds whose molecules have unsaturated bonds [1,91,101,108,109,153-155]. The au-... 

A 30-min 99/1->93/7 chloroform/ethanol gradient was used with a silica column (A = 254nm) to characterize styrene/methyl and ethyl methacrylate copolymers [755]. That the ethanol content was critical was shown through a series of chromatograms for a 50/50 styrene/methyl methacrylate co-polymer and a 35/65 styrene/ethyl methacrylate co-polymer. For 25 pL injections of 0.1% w/v samples, the 50/50 co-polymer completely eluted with a 97/3 chloroform/ethanol mobile phase but was completely adsorbed to the silica at 99/1. Similarly, the 35/65 copolymer eluted at 95/5 chloroform/ethanol and did not elute at 98/2. Temperature effects (40-70°C) on the level of ethanol needed for elution were tabulated for these co-polymers as well. 

The adsorption of block and random copolymers of styrene and methyl methacrylate on to silica from their solutions in carbon tetrachloride/n-heptane, and the resulting dispersion stability, has been investigated. Theta-conditions for the homopolymers and analogous critical non-solvent volume fractions for random copolymers were determined by cloud-point titration. The adsorption of block copolymers varied steadily with the non-solvent content, whilst that of the random copolymers became progressively more dependent on solvent quality only as theta-conditions and phase separation were approached. 

Poly(methyl methacrylate) provides a level of stabilization even though the solution in CCl is below the 0-temperature. All the copolymers, both random and block, are better stabilizers than PMM, the methacrylate units acting as anchors, with stabilizing sequences of styrene loops, of block copolymers, or mixed loops and tails, of random copolymers, at better than 0-conditions. Higher M.W. polystyrenes give silica dispersions too unstable to measure by our optical method the sediment volumes are between those of poly(methyl methacrylate) solutions and pure solvent. 

Fig. 1 Chemical structures of the polymers commonly used for preparation of beads poly (styrene-co-maleic acid) (=PS-MA) poly(methyl methacrylate-co-methacrylic acid) (=PMMA-MA) poly(acrylonitrile-co-acrylic acid) (=PAN-AA) polyvinylchloride (=PVC) polysulfone (=PSulf) ethylcellulose (=EC) cellulose acetate (=CAc) polyacrylamide (=PAAm) poly(sty-rene-Wocfc-vinylpyrrolidone) (=PS-PVP) and Organically modified silica (=Ormosil). PS-MA is commercially available as an anhydride and negative charges on the bead surface are generated during preparation of the beads...

Braun et al. [258] used a combination of tert-butyllithium (t-BuLi) and tetramefhy-lethylenediamine to create initiator sites at the surface of carbon black for the LASIP of styrene. Schomaker et al. [259] first immobilized a methyl methacrylate derivative on colloidal silica and after activation by a Grignard reagent polymerized MMA. 

Hadziioannou et al. [296] employed an analog surface-bond initiator for RAFT-SIP on silica substrates to prepare homogeneous block copolymers of styrene and methyl methacrylate. A patterned substrate was prepared by selective deposition of the initiator. 

Tsubokawa et al. (12-14) have introduced radical sources of azo or peroxy groups by another methods, and successively conducted the radical polymerization of vinyl compounds, such as styrene or methyl methacrylate, to give polymer-grafted particles see Reaction (3). The grafting by the radical polymerization of methyl methacrylate, initiated from a peroxy group introduced on silica, takes place at relatively high efficiency, compared with those from azo group-introduced particles. 

Fig. 12.1.1 Dependence of order parameter, S. of the secondary polymer, spin-labeled poly (methyl methacrylate) (PMMA) and polystyrene (PST), bound to poly(maleic anhydride—styrene )-grafted silica on hexane content in ethyl acetate-hexane cosolvent. Numbers in parentheses are number average molecular weight of the secondary polymer. (From Ref. 48.)...

Fig. 12.1.4 Immobilization of bovine serum albumin on colloidal silica grafted with poly (maleic anhydride-styrene) (O), poly(maleic anhydride-methyl methacrylate) ( ), and poly (ethylene glycol)-poly(maleic anhydride-styrene) (A). (Front Ref. 42.)...

Porous silica is most widely used as adsorbent, but bonded phase materials with polar groups or crosslinked acrylonitrile39> have also been tested. Silica requires painstaking control of activity. In the separation of poly(styrene-co-methyl methacrylate) samples with dichloroethane—chloroform mixtures, clearer results were obtained with a silica column previously rinsed with methanol40. Continuously decreasing activity of silica columns was observed in the elution of poly(styrene-co-methyl acrylate) with CCU-methyl acetate mixtures38). 

Fig. 9. Copolymer separation. Gradient elution of the mixture of three poly(styrene-co-methyl methacrylate) samples on a silica column (250 x 6 mm d0 = 5nm dP = 9pm). Gradient 1,2-dichloroethane/tetrahydro-...

Fig. 10. Copolymer separation. Gradient elution of the mixture of seven poly(styrene-co-methyl methacrylate) samples on a silica column (150x4.6 mm d0 = 6 nm dP = 5 pm). Gradient iso-octane/(tetrahydrofuran +10% methanol), 10% B (0 min), 50% (8 min), 80% (10 min), 100% (11 min) flow rate 1 ml/min, reduced to 0.3 ml/min after 9.9 min. Methyl methacrylate content (wt %) indicated. Molar mass values 11.4 — 160 kg/mol 23.8 — 250 37.0 — 150 49.5 — 185 64.0 — 235 76.2 — 220 88.5 — 220. Column temperature 50 °C. (By courtesy of Elsevier Science Publ. [43])...

In the polymer impregnated gels, some porosity typically remains. Although some copolymers of methyl methacrylate, butadiene and styrene have been used to impregnate silica, the best known system is still silica impregnated with polymethyl methacrylate (PMMA)150-153. While this type of hybrid was important at first, it has been surpassed by other methods of hybrid synthesis that are simpler, with fewer steps and shorter times. 

The second step, the Interpretation in terms of -potentials and conductivities. requires theory. For non-dilute dispersions this implies consideration of hydrodynamic and electrostatic particle Interaction. James et al. l, working with poly(styrene) and poly(methyl methacrylate) latlces, alumina and silica sols confirmed that u obtained from ESA agreed with the (static) values, obtained mlcro-electrophoretlcally. if the theory by O Brien (see [4.3.45-481) was applied in the analysis. Marlow et al. already noted the same for dilute rutile dispersions their mobility (or Q curves as a function of pH agreed with those in flg. 3.63. 

Other organic and inorganic binders have also been tested. Polymerization of styrene or methyl methacrylate in cancrinite-monomer mixtures produces hard, rugged products. Sodium silicate solution mixed with powdered silica also appears to be an effective binder for the cancrinite. 

The free radical polymerization of styrene initialized by iniferter is influenced by chemical binding of iniferter on the surface of the silica." This reaction is used for grafting the polymer onto the surface of the silica. A similar approach is used when carbon whisker is incorporated during the graft-polymerization of methyl methacrylate. Depending on how the whisker is prepared, surface conversion can be increased up to twelve times compared to a polymerization with no whisker present. The addition of graphite to the poly esterification reaction doubles the molecular weight of the polymer. ... 

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