Water-soluble vinylic monomer

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

Many water-soluble vinyl monomers may be polymerized by the emulsion polymerization technique. This technique, which differs from suspension polymerization in the size of the suspended particles and in mechanism, is widely used for the production of a number of commercial plastics and elastomers. While the particles in the suspension range from 10 to 1000 nm, those in the emulsion process range from 0.05 to 5 nm in diameter. The small beads produced in the suspension process may be separated by filtering, but the latex produced in emulsion polymerization is a stable system in which the charged particles cannot be recovered by ordinary separation procedures. 

Table 3. Copolymerization of MAOFU, MAOT, AOT, and MAOA with water-soluble-vinyl monomers...

Such a substrate effect is observed in a wide variety of hydrogels prepared from water-soluble vinyl monomers (e.g., the sodium salt of styrene sulfonate, acrylic acid, and acrlyamide), and on various hydrophobic substrates, such as Teflon, polyethylene, polypropylene, PVC, and polymethyl methylacrylate (PMMA) [52]. This template effect is due to retardation of the radical polymerization near the rough and hydrophobic substrates that trap oxygen at the solid surface [82]. 

To test whether any free aryl radicals can be formed in the course of reactions of the Sandmeyer type, decompositions of aqueous solutions of stabilized diazonium salts, such as the borofluorides, have been carried out in the absence of oxygen or of traces of oxidizing agents, in the presence of the water-soluble vinylic monomers, acrylonitrile and methyl methacrylate. Polymerization has regularly been observed when one-electron transfers of type (3) above are possible and the isolated polymers, after washing free from simple aromatic materials, have been shown, by inspection of infrared spectra and often by detection of halogens derived from the diazonium salts, to contain aromatic nuclei as end groups. 

Cryogels from Water-Soluble Vinyl Monomers. 209... 

While not strictly considered emulsions, two other systems may be classified in this category, both of which comprise very small particles of silicone fluids in aqueous dispersions. The first method of preparing these microdroplets involves in situ polymerization of a water-soluble vinyl monomer or mixtures of said monomer and acryl comonomers. The silicone fluids are first dispersed into microdroplets in the water phase by means of high-speed agitation and then the vinyl monomers or cationic polymers are added at elevated temperatures in the presence of free-radical catalysts. The resulting aqueous polymer matrix contains stable, discreet microdroplets of the silicone fluids. The second method utilized to prepare such a fine dispersion is very-high-pressure injection of silicone into the aqueous phase. These microdroplets have been referred to as nanoparticles, but they are actually nanometer-sized fluid droplets as opposed to nanometer-sized sihcone resin particles, which are referred to by the same term (86). Both of the systems described above have been claimed to readily deposit onto hair and skin, and to increase ease of formulation (87,88). 

Uniform-submicron size polymer spheres can be made through emulsion pol)mierization [106]. When a sparingly water-soluble vinyl monomer like styrene tiiat pol)rmeri2es by a free radical mechanism is dispersed in water in the presence of a surfactant and a water-soluble initiator, uniform-sized polystyrene beads can be obtained by controlling the number of micelles and ensuring that each micelle traps an initiator at about ttie same time. 

Emulsion polymerization is widely used to produce polymers in the form of emulsions, such as paints and floor polishes. It also used to polymerize many water insoluble vinyl monomers, such as styrene and vinyl chloride. In emulsion polymerization, an agent emulsifies the monomers. Emulsifying agents should have a finite solubility. They are either ionic, as in the case of alkylbenzene sulfonates, or nonionic, like polyvinyl alcohol. 

Polymerization of vinyl chloride occurs through a radical chain addition mechanism, which can be achieved through bulk, suspension, or emulsion polymerization processes. Radical initiators used in vinyl chloride polymerization fall into two classes water-soluble or monomer-soluble. The water-soluble initiators, such as hydrogen peroxide and alkali metal persulfates, are used in emulsion polymerization processes where polymerization begins in the aqueous phase. Monomer-soluble initiators include peroxides, such as dilauryl and benzoyl peroxide, and azo species, such as 1,1 -azobisisobutyrate, which are shown in Fig. 22.2. These initiators are used in emulsion and bulk polymerization processes. 

Both the poly (vinyl acetate)-poly (vinyl alcohol) and styrene-shellac examples of colloid participation in the polymerization require much investigation especially with respect to whether grafting to the colloid occurs in aqueous solutions or at the particle surface. The former would appear more likely for the relatively water soluble vinyl acetate monomer, while the latter should be favored for the less soluble styrene. In any case, both would result in identical particle stabilization. 

The copolymerization of monomers where one of the monomers acts as the hydrophobe was reported by Reimers and Schork [26]. MMA was copolymerized with p-methylstyrene, vinyl hexanoate, or vinyl 2-ethylhexanoate. The resulting copolymer composition tended to follow the predictions of the reactivity ratios, i.e., the reaction progresses as a bulk reaction. In contrast, copolymer compositions obtained from the (macro)emulsion copolymerizations tended to be more influenced by the relative water solubility of the comonomer and mass transfer. Wu and Schork used monomer combinations with large differences in reactivity ratios and water solubility vinyl acetate/butyl acrylate,... 

A new process from the paint industry may have application for the suspension coating of pesticide crystals [25]. Low molecular weight water-soluble vinyl polymer chains are synthesized and the process stopped with a terminal vinyl group on each polymer chain. Hydrophobic acrylic monomers are then idded to create the hydrophobic strongly adsorbing backbone polymer. As each water-soluble polymer terminal vinyl group reacts with the growing hydrophobic backbone polymer it becomes inserted like a tooth on a comb. Indeed, these polymer structures are referred to as comb polymers. 

On this vinylated silica gel, CyD is imprinted (this technique is applicable to versatile water-soluble functional monomers). Acryloyl-CyD (90 mg, 67 pmol), MBAA (60 mg, 390 prnol), and the template molecule (30 pmol) are dissolved in 5 mM ofTris buffer solution (pH 8.0, 5 mL), and then vinylated silica gel (600 mg) is dispersed. The polymerization is started by adding potassium persulfate (7 pmol, 2 mg) and N,N,N, N -tetramethylethylenediamine (20 prnol, 3 pL) as an initiator system under nitrogen at 37 °C. After 1 h, the solid part is collected and washed with large amounts of water and methanol to remove the template and unreacted monomers. The polymer/silica-gel conjugates thus obtained are then packed into a stainless column and used as a stationary phase of HPLC. During the analysis, the column pressure is always kept normal. 

Now consider the case of polymerisation of monomers with appreciable water solubility and their copolymerisation with less water-soluble comonomers. Monomers such as vinyl acetate or methyl acrylate have sufficient water solubility to permit their rapid polymerisation in the water phase even in the absence or after the disappearance of surfactant micelles. New polymer particles can be formed as long as the monomer concentration in the water phase remains high enough. In most cases, there is strong monomer/polymer affinity so that more and more monomer will be extracted from the water phase. As polymer concentrations increase, polymerisation in the water phase will finally cease and with it the formation of new particles. Henceforth, conversion will proceed at the surface of the polymer/monomer particles in much the same way as in the case of water-insoluble monomers after the disappearance of the surfactant micelle. 

Because of the polymerization and monomer transport, the polymer particles grow in size, and after some time the monomer droplets disappear. This marks the end of Interval II. The monomer conversion at which Interval II ends depends on the capability of the polymer particle to be swollen by monomer. The higher the maximum swelling, the earlier the monomer droplets disappear. In general, the more water-soluble the monomer, the higher the maximum swelling, and hence the lower the monomer conversion at the end of Interval II. Thus, the transition from Interval II to Interval III occurs at about 40% conversion for styrene and at about 15% conversion for vinyl acetate. This means that most monomer polymerizes in Interval III (Figure 6.2(d)). In this interval, monomer concentration in the polymer particles decreases continuously. The final product is a waterborne, concentrated (50-60 wt.% solids) dispersion of tiny (80-500 nm in diameter) polymer particles called latex. 

The kinetic behavior in the emulsion copolymerization of VC and vinyl monomers has not been described till now. The emulsion copolymerization appears to be very complex due to large differences in water solubilities of monomers and polymers, the solubility of polymers in their monomers, the chain-transfer to monomers and the reactivities of monomer and growing radicals. 

Another way to improve the solubility characteristics of hydrophobically associating polymers is through incorporation of water-soluble, ionic monomers into the polymer. Carboxylate functionality has been introduced into RAM polymers by either copolymerization with acrylic acid salt or by a postpolymerization partial hydrolysis of the acrylamide groups. Incorporating about 20 mol% sodium acrylate functionality, significantly improves solubility of these HRAM polymers. Sulfonate groups can be introduced by copolymerizing with a sulfonate monomer such as vinyl sulphonate or 2-acrylamido-2-methylpropane sulfonate, AMPS. We call these polymers SRAM. 

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