Suspension in polymerization

Metzner, A. B. 1985. Rheology of suspensions in polymeric liquids. J. Rheol. 29 139-115. 

Encapsulation of drug (liquid, solid or suspension) in polymeric matrix release is controlled by diffusion through capsule wall. 

M. Munzer, E. Trommersdorff, Polymerizations in suspension , in Polymerization Processes , CE. Schildknecht, I. Skeist, eds, WUey Interscience, New York, Ch. 5, 1977... 

Nicodemo, L. and Nicolais, L. (1974) Viscosity of bead suspensions in polymeric solutions, /. Appl. Polym. Sci., 18,2809-18. 

An important step in tire progress of colloid science was tire development of monodisperse polymer latex suspensions in tire 1950s. These are prepared by emulsion polymerization, which is nowadays also carried out industrially on a large scale for many different polymers. Perhaps tire best-studied colloidal model system is tliat of polystyrene (PS) latex [9]. This is prepared with a hydrophilic group (such as sulphate) at tire end of each molecule. In water tliis produces well defined spheres witli a number of end groups at tire surface, which (partly) ionize to... 

Styrene is a colorless Hquid with an aromatic odor. Important physical properties of styrene are shown in Table 1 (1). Styrene is infinitely soluble in acetone, carbon tetrachloride, benzene, ether, / -heptane, and ethanol. Nearly all of the commercial styrene is consumed in polymerization and copolymerization processes. Common methods in plastics technology such as mass, suspension, solution, and emulsion polymerization can be used to manufacture polystyrene and styrene copolymers with different physical characteristics, but processes relating to the first two methods account for most of the styrene polymers currendy (ca 1996) being manufactured (2—8). Polymerization generally takes place by free-radical reactions initiated thermally or catalyticaHy. Polymerization occurs slowly even at ambient temperatures. It can be retarded by inhibitors. 

Suspension polymerization of water-insoluble monomers (e.g., styrene and divinylbenzene) involves the formation of an oil droplet suspension of the monomer in water with direct conversions of individual monomer droplets into the corresponding polymer beads. Preparation of beaded polymers from water-soluble monomers (e.g., acrylamide) is similar, except that an aqueous solution of monomers is dispersed in oil to form a water-in-oil (w/o) droplet suspension. Subsequent polymerization of the monomer droplets produces the corresponding swollen hydrophilic polyacrylamide beads. These processes are often referred to as inverse suspension polymerization. 

Synthetic organic polymers, which are used as polymeric supports for chromatography, as catalysts, as solid-phase supports for peptide and oligonucleotide synthesis, and for diagnosis, are based mainly on polystyrene, polystyrene-divinylbenzene, polyacrylamide, polymethacrylates, and polyvinyl alcohols. A conventional suspension of polymerization is usually used to produce these organic polymeric supports, especially in large-scale industrial production. 

Suspension (co)polymerization is carried out in aqueous solutions of monomers dispersed in the form of 0.1-5 mm diameter droplets by stirring in nonmixed water-organic liquids in the presence of initiators. The organic liquids that are not dissolving monomers and (co)polymers are represented by solvents that either form azeotropic water mixtures (toluene, heptane, cy-... 

Many initiators, such as alkyl and aryllithium and sodium and lithium suspensions in liquid ammonia, effect the polymerization. For example, acrylonitrile combined with n-butyllithium forms a carbanion intermediate ... 

Solutions of some polymeric materials also have similar rheological properties and behave in the same way as suspensions in pipe flow. However, they do in time break down and they do not give any appreciable increase in buoyancy as their densities differ little from that of water. 

A polymer containing side-chain benzylphosphonium residues has been prepared and used in olefin synthesis. A suspension in THF was treated with base and benzaldehyde overnight and the polymeric phosphine oxide was then removed by filtration. The yields of stilbenes, 40% with potassium t-butoxide and 60% with sodium hydride, were not improved by using an excess of base or of aldehyde. 

Figure 2. Representative optical micrographs of poly-HEMA cross-linked with EDMA. (a) and (b) represent the gel-type polymer produced by suspension co-polymerization in the dry and swollen state, respectively, (c) and (d) represent the macroreticular polymer produced by suspension co-polymerization in the presence of a porogen (toluene), in the dry and swollen (vide infra) state, respeetively [13], (Reprinted from Ref [15], 1996, with permission from Elsevier.)...

The concept of extractive reaction, which was conceived over 40 years ago, has connections with acid hydrolysis of pentosans in an aqueous medium to give furfural, which readily polymerizes in the presence of an acid. The use of a water-immiscible solvent, such as tetralin allows the labile furfural to be extracted and thus prevents polymerization, increases the yield, and improves the recovery procedures. In the recent past an interesting and useful method has been suggested by Rivalier et al. (1995) for acid-catalysed dehydration of hexoses to 5-hydroxy methyl furfural. Here, a new solid-liquid-liquid extractor reactor has been suggested with zeolites in protonic form like H-Y-faujasite, H-mordenite, H-beta, and H-ZSM-5, in suspension in the aqueous phase and with simultaneous extraction of the intermediate product with a solvent, like methyl Aobutyl ketone, circulating countercurrently. 

In the discussion above it has been shown that the lipid can been polymerized through UV irradiation of its aqueous suspension. The polymerization of the system improves the stability of the synthetic liposomes. Since there is an acetal linkage introduced between the polymer chain and the amphiphilic structure, this linkage can be slowly hydrolyzed in aqueous systems to separate the polymer chain from the lipid. 

Some examples in which this agitation effect is more likely to occur are reactions during which the viscosity changes significantly, such as in polymerizations, and reactions with suspensions. Equipment dimensions, type of agitators, and type of solvents and coolants used affect the heat transfer as well [174],... 

STYR0P0R, BASF - polymerization of styrene monomer in suspension in the presence of pentane as the blowing agent. Manufacture of new insulating packaging materials, etc. Suspension polymerization of crystal polystyrene in Ludwigshafen. 

A common method to slip-cast ceramic membranes is to start with a colloidal suspension or polymeric solution as described in the previous section. This is called a slip . The porous support system is dipped in the slip and the dispersion medium (in most cases water or alcohol-water mixtures) is forced into the pores of the support by a pressure drop (APJ created by capillary action of the microporous support. At the interface the solid particles are retained and concentrated at the entrance of pores to form a gel layer as in the case of sol-gel processes. It is important that formation of the gel layer starts... 

Figure 3 Molecular relaxivities of liposomes with different Gd-containing membranotropic chelators. Liposomes (egg lecithin cholesterol chelator = 72 25 3) were prepared by consecutive extrusion of lipid suspension in HEPES buffered saline, pH 7.4, through the set of polycarbonate filters with pore size of 0.6, 0.4, and 0.2 mm. Liposome final size was between 205 and 225 nm. Gd content determination was performed by Galbraith Laboratories, Inc. The relaxation parameters of all preparations were measured at room temperature using a 5-MHz RADX nuclear magnetic resonance proton spin analyzer. The relaxivity of liposomes with polymeric chelators is noticeably greater because of the larger number of Gd atoms bound to a single lipid residue [16].

Water insoluble monomers such as vinyl chloride may be polymerized as suspended droplets (10-1000 nm in diameter) in a process called suspension (pearl) polymerizations. Coalescence of droplets is prevented by the use of small amounts of water-soluble polymers, such as PVA. The suspension process is characterized by good heat control and ease of removal of the discrete polymer particles. 

Munzer, M. andE. Trommsdorff, Polymerizations in Suspension, Chap. 5 in Polymerization Processes,... 

Polymerization of Vinyl Acetate in Suspension (Bead Polymerization)... 

For liquid (e.g., solution, suspension, elixir) and semisolid (e.g., creams, ointments) dosage forms, a change to or in polymeric materials (e.g., plastic, rubber) of primary packaging components, when the composition of the component as changed has never been used in a CDER-approved product of the same dosage form and same route of administration. For example, a polymeric material that has been used in a CDER-approved topical ointment would not be considered CDER-ap-proved for use with an ophthalmic oinhnent. 

When butadiene was polymerized in the presence of a PVC suspension in chlorobenzene using a catalyst system based on Et2AlCl, the methanol-precipitated reaction product had little or no solubility in refluxing hexane. The soluble fraction, when obtainable, was identifiable as a greater than 90% cw-1,4-polybutadiene. In this case, the hexane-insoluble residue was essentially completely soluble in tetrahydrofuran, probably owing to the low molecular weight of the polybutadiene in the PVC-cw-1,4-polybutadiene reaction product. 

The parameter r2 is independent of the initiator type for the emulsion, however, and is slightly higher than that obtained in benzene (r2=1.23) (Table 3). This behavior results from good compatibility of the macromonomer with poly-BzMA. Therefore the reactivity of the macromonomer does not depend so much on the reaction medium type. In contrast, reversed apparent reactivity was observed in heptane in which the clear solution of monomer turned into a polymer suspension upon polymerization. Since BzMA is soluble in the medium, it has been suggested that the polymerization occurs preferentially on the (inverse) micelle surface which is enriched by the macromonomers. 

The viewpoint sketched above has been so far developed and applied mainly in the context of mechanics and thermodynamics of complex fluids (Grmela, 2009 and references cited therein, also Section 3.1.6 of this review). The coupling between macroscopic (hydrodynamic) flow behavior and the behavior of a microstructure (e.g., macromolecules in polymeric fluids or suspended particles or membranes in various types in suspensions) is naturally expressed in the multiscale setting. In this review we shall include in illustrations also... 

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