Acrylamide based polymers

Hydrolysis of amide groups to carboxylate is a major cause of instability in acrylamide-based polymers, especially at alkaline pH and high temperatures. The performance of oil-recovery polymers may be adversely affected by excessive hydrolysis, which can promote precipitation from sea water solution. This work has studied the effects of the sodium salts of acrylic acid and AMPS, 2-acrylamido-2-methylpropanesulfonic acid, as comonomers, on the rate of hydrolysis of polyacrylamides in alkaline solution at high temperatures. Copolymers were prepared containing from 0-53 mole % of the anionic comonomers, and hydrolyzed in aqueous solution at pH 8.5 at 90°C, 108°C and 120°C. The extent of hydrolysis was measured by a conductometric method, analyzing for the total carboxylate content. 

The molecular weights and molecular weight distributions of lower molecular weight polymeric flocculants are determined by viscosity measurements. High molecular weight acrylamide-based polymers are characterized by light scattering techniques. 

Based on animal studies and mutagenicity studies, trace amounts of organic polymers do not appear to present a toxicity problem in drinking water. The reaction products with both chlorine and ozone also appear to have low toxicity. The principal concern is the presence of unreuctcd monomer and other toxic and potentially carcinogenic nonpolymeric organic compounds in commercial polymeric flocculants. The principal contpuimds are acrylamide in acrylamide based polymers, dimethyldiallyammonium chloride in allylie polymers, and epichlorohydrin and chlorinated propanols in polyamines, as well as the rcaclion products of these compounds with ozone and chlorine. 

Commonly employed water-insoluble supports for the covalent attachment of enzymes include synthetic supports such as acrylamide-based polymers, maleic anhydride-based polymers, methacrylic acid-based polymers, styrene-based polymers, and polypeptides, and natural supports such as agarose (Sepharose), cellulose, dextran (Sephadex), glass, and starch (Zaborsky, 1973). 

The values of KM and rmax for an enzyme (21°C and pH = 7.1) are 0.004 kmol/m3and 10 kmol/m3s, respectively. We immobilized this enzyme by attaching it covalently to acrylamide-based polymers that can be assumed to have spherical shape (diameter = 1 mm). The effectiveness of the immobilized enzyme was found to be 70 percent of the free enzyme when the concentration of the substrate was 0.5 kmol/m3. The reaction was carried out in a stirred reactor with an agitation speed of 50 rpm. (a) Estimate the concentration of the substrate at the surface of the immobilized enzyme, (b) Estimate ks a. 

Clinical applications of thermosensitive hydrogels based on NIPAAm and its derivatives have limitations [121], The monomers and cross-linkers used in the synthesis of the hydrogels are still not known to be biocompatible and biodegradable. The observation that acrylamide-based polymers activate platelets upon contact with blood, together with the unclear metabolism of poly(NIPAAm), requires extensive toxicity studies before clinical applications can merge. 

It is also conceivable that steric stabilization plays a role in the inhibition of hemagglutination by the longer polymers although it should be noted that the polymers generated via ROMP are considerably smaller than the acrylamide- based polymers that benefit from the steric mechanism. Moreover, the assays for the ROMP-derived ligands do not involve direct binding to a surface-immobilized receptor. It is also possible that the ability of ligands to cluster multiple copies of ConA is a key factor in their potency. 

Reten . [Hercules] Acrylamide-based polymers flocculant, retention aid, thickener, suspending agent, leveling agent, film-former, antistat, crosslinking agent for pulp and paper, hair treatment, adhesives. 

Perkin Elmer Specially formulated acrylamide-based polymer Proteins http //las. perkinelmer.com... 

The acrylamide-based polymers used in the study were obtained commercially in powder form. The homopolymers designated as PS-2806, SPP-34 and ALD-18127-7 were supplied by Polysciences, Scientific Polymer Products and Aldrich respectively. Supplied also by Polysciences were our two poly(acrylamide-co-acrylic acid) samples of high and low carboxyl content, PS-2220 and PS-4652. Table I illustrates the molecular weight distribution of these samples as determined by aqueous GPC/Laser light scattering. The acrylic acid contents of PS-2220 and PS-4652 copolymers measured by 90 MHz C NMR were approximately 63% and 15% respectively. Both the GPC and the NMR analyses indicated PS-2220 contained appreciable amounts of impurities. 

Considerable research has been conducted to identify water soluble polymers which can efficiently control the flow properties of displacement fluids for enhanced oil recovery.Two main types of polymeric viscosifiers have emerged from this research which rely mainly on ultra high molecular weight for thickening efficiency natural biopolymers such as Xanthan or Scleroglucain and synthetic acrylamide based polymers. Although these polymers possess many useful characteristics, the reservoir conditions in which they can provide adequate mobility control are limited. For example, the biopolymers provide excellent mechanical stability and salt tolerance, however, further improvement in high temperature stability would be desirable. 

Viscosification with acrylamide based polymers depends not only on high molecular weight but also on chain expansion due to ionic charge repulsion or the polyelectrolyte effect. 

The nature of the association maintains a locally effective shielding of the sulfonate anions within the aggregate and preservation of the clustered structure. This suggests that for these block polymer structures, the energetics of maintaining hydrophobic association are more favorable than monomer dispersion due to ionic repulsion. This was further demonstrasted by the extreme salt sensitivity of these polymers to solution ionic strength. Small amounts of sodium chloride resulted in polymer precipitation and of course loss of viscosification. This precludes the use of these particular polymers for chemically enhanced oil recovery and indicates the need for nonionic functionality to provide water solubility. To further pursue this approach acrylamide based polymers were studied. 

Hydrophobically associating acrylamide based polymers were explored as a means of alleviating the salt sensitivity observed in the block systems. A micellar polymerization technique was developed to enable preparation of random copolymers of acrylamide and N-n-alkylacrylamide. When these copolymers were dissolved in an aqueous solvent, the hydrophobic groups associated to minimize their exposure to water. The hydrophobic associations provided an additional dimension to polymer molecular weight and chain expansion by ionic groups for the control of aqueous fluid rheology. 

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. 

Polymer Synthesis. Acrylamide-based Polymers, Acrylamide-based polymers were prepared in an 0.5 M NaCl aqueous solution at 30 C using KPS as the free radical initiator. Total monomer concentration was held constant at 0.45 M and the pH adjusted so that all monomers were in die ionized form. Reactions were terminated at <60% conversion by precipitation in acetone. The polymers were fiirther purified by dialysis against deionized water. In the following discussion, the number appended to the polymer series is representative of the mol% of the respective sulfobetaine incorporated into the polymer (See Tables 1,2,3, and 4). 

Table 1. Particle size comparisons between acrylamide-based polymers...

Scoggins and Miller (1975,1979) developed a method for the determination of acrylamide-based polymers in brine solution which depends on the presence of the primary amide group, —C=ONH2- This method depends on the bromine oxidation of the amide functional group through the following reaction at pH 3.5 ... 

It is well established that the stability of the aqueous polymer solutions can be influenced by one or more of a complex set of factors including polymer composition, salt environment, temperature, pH, oxidative effects, bacteria, etc. [11,15,16,24]. The influence of these factors has been considered extensively in studies of acrylamide-based polymers and biopolymers to control mobility in Chemically Enhanced Oil Recovery, CEOR, processes. With respect to polyacrylamide (PAM) and partially hydrolyzed polyacrylamide (HPAM), hydrolysis is a major factor influencing solution stability. 

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