Solubilities of acrylamide

Acrylamide is the most important and the simplest of the acrylic and methacrylic amides. Acrylamide is a colorless crystalline solid. The basic physical properties and solubilities of acrylamide are given in Table I. Acrylamide is a severe neurotoxin and is a cumulative toxicological hazard. 

Because the solubility of acrylamide (JEL), water ( ), and the surfactants in ethane or propane is low, the viscosity of the continuous phase was taken to be that of the pure fluid. The viscosity of the various ethane/propane mixtures was calculated using a reduced-density correlation developed by Dean and Stiel (IQ.), which is reported to be accurate to within 2 to 4% for light hydrocarbon mixtures. The density of the ethane/propane mixtures was either calculated via a modified Benedict-Webb-Rubin equation of state (11.) or, in some cases, measured using a Mettler-Paar DMA-512 vibrating tube densimeter. The densimeter was thermostated via a circulating water bath to within 0.01 C, and calibrated using water and propane at the ten ratures of interest. 

The kinetics of inverse emulsion polymerization can be classified more or less arbitrarily into two subclasses according to the solubility of the initiator. Note that the solubility in water of oil-soluble initiators was found to be oihanced (up to a factor of 3) by the presence of monomo [23,28,29], making possible initiation by radical pairs formed in the aqueous dispersed phase. On the other hand, homogeneous nucleation mechanisms generating oligoradicals in the continuous phase can also be operative in inverse emulsions due to the maiginal solubility of acrylamide in organic media (1.6 wt% in isoparaffinic solvents and 2 wt% in toluene) [3]. 

Although acrylamide-based polymers are rather hydrophilic, they are soft and often swell excessively in water. Therefore, these stationary phases are currently not well suited for HPLC. In addition, the high solubility of acrylamides in water makes them less practical for polymerization in aqueous suspensions. In contrast, acrylates and methacrylates containing hydroxyl groups in lateral chains can be used for the preparation of beads by means of typical suspension polymerization. This is why the majority of commercially available rigid hydrdophlic beads suitable for HPLC are manufactured from these monomers. Some of these typical chemistries were already shown in Fig. 2. 

Acrylamide copolymers designed to reduce undesired amide group hydrolysis, increase thermal stability, and improve solubility in saline media have been studied for EOR appHcations (121—128). These polymers stiH tend to be shear sensitive. Most copolymers evaluated for EOR have been random copolymers. However, block copolymers of acrylamide and AMPS also have utiHty (129). 

The main application of acrylamide is the preparation of water-soluble polymers and copolymers. Smaller... 

Acrylamide readily undergoes polymerization by conventional free radical methods, ionizing radiation, ultrasonic waves, and ultraviolet radiation. The base-cata-lized hydrogen transfer polymerization of acrylamide yields poly-/3-alanine (Nylon 3) a water insoluble polymer that is soluble in certain hot organics. All current industrial production is believed to be by free radical polymerization. 

In the case of photoinitiated polymerization, an oxygen-free aqueous solution of acrylamide with a concentration of about 50% mixed with a photosensibilizer and other required additives is passed through a column-type apparatus with exterior water-cooling. A thin layer of the solution is exposed to a mercury lamp, acquires the consistency of a plastic film, which then can be passed through a second exposure zone, and is crushed and dried. Acrylamide polymers produced by this method are easily soluble and have a low residual monomer content. 

Anionic polyacrylamide was prepared by gamma radiation-initiated copolymerization of acrylamid with sodium acrylate in aqueous solution at optimum conditions for the copolymerization [17]. The copolymerization process produces water-soluble poly (acrylamide-sodium acrylate [pAM-AANa] of high molecular weight [17,54]. 

Iwai and coworkers [56] have introduced a novel type of multicomponent photoinitiating system for water-soluble monomer (acrylamide, acrylic acid, acrylonitrile, etc). 

Acrylamide copolymers designed to reduce undesired amide group hydrolysis, increase thermal stability, and improve solubility in saline media have been synthesized and studied for EOR applications. These polymers still tend to be shear sensitive. Acrylamide comonomers that have been used include 2-acrylamido-2-methylpropane sulfonate, abbreviated AMPS, (1,321-324), 2-sulfo-ethylmethacrylate (325,326), diacetone acrylamide (324, 326), and vinylpyrrolidinone (327,328). Acrylamide terpolymers include those with sodium acrylate and acrylamido-N-dodecyl-N-butyl sulfonate (329), with AMPS and N,N-dimethylacrylamide (330), with AMPS and N-vinylpyrrolidinone (331), and with sodium acrylate and sodium methacrylate (332). While most copolymers tested have been random copolymers, block copolymers of acrylamide and AMPS also have utility in this application (333). 

In the conventional emulsion polymerization, a hydrophobic monomer is emulsified in water and polymerization initiated with a water-soluble initiator. Emulson polymerization can also be carried out as an inverse emulsion polymerization [Poehlein, 1986]. Here, an aqueous solution of a hydrophilic monomer is emulsified in a nonpolar organic solvent such as xylene or paraffin and polymerization initiated with an oil-soluble initiator. The two types of emulsion polymerizations are referred to as oil-in-water (o/w) and water-in-oil (w/o) emulsions, respectively. Inverse emulsion polymerization is used in various commerical polymerizations and copolymerizations of acrylamide as well as other water-soluble monomers. The end use of the reverse latices often involves their addition to water at the point of application. The polymer dissolves readily in water, and the aqueous solution is used in applications such as secondary oil recovery and flocculation (clarification of wastewater, metal recovery). 

Polymerization reactions in aqueous medium can be carried out in homogeneous solution if the monomers and the polymers are soluble in water as in the case of acrylamide or methacrylic acid (see Examples 3-5,3-9, and 3-35). Since most of the monomers are only sparingly soluble in water, suspension or emulsion techniques have to be applied in these cases. 

For example, an aqueous suspension homopolymerization would normally not be appropriate for water-soluble monomers such as acrylamide or acrylic acid. For such cases, it may be possible that with high levels of neutral salts, the water solubility of such monomers may be reduced to permit the use of suspension polymerization techniques. Other monomers may have other unique properties that require some modifications of the basic procedures. 

Water-in-oil concentrated emulsions have also been utilised in the preparation of polymer latexes, from hydrophilic, water-soluble monomers. Kim and Ruckenstein [178] reported the preparation of polyacrylamide particles from a HIPE of aqueous acrylamide solution in a non-polar organic solvent, such as decane, stabilised by sorbitan monooleate (Span 80). The stability of the emulsion decreased when the weight fraction of acrylamide in the aqueous phase exceeded 0.2, since acrylamide is more hydrophobic than water. Another point of note is that the molecular weights obtained were lower compared to solution polymerisation of acrylamide. This was probably due to a degree of termination by chain transfer from the tertiary hydroxyl groups on the surfactant head group. 

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