Methacrylic acid

Abstract: Stability of aqueous α-Al2O3 suspensions with Na+ salt of poly(methacrylic acid) (PMAA-Na) polyelectrolyte was studied as a function of pH. At a given pH, the transition from the flocculated to the dispersed state corresponded to the adsorption saturation limit of the powders by the PMAA. As the pH was decreased, the adsorption saturation limit increased until insolubility and charge neutralization of the PMAA was approached. The critical amount of PMAA required to achieve stability is outlined in a stability map.

Abstract: Robust multilayers can be formed on solid surfaces, and subsequently destroyed by changing the environmental conditions, by the layer-by-layer sequential assembly of monomolecular films of a polyacid and polybase from aqueous solution. Interlayer hydrogen bonding produces stable multilayers up to the point where altered pH or other environmental stimulus introduces an unacceptably large electrical charge within them. This is demonstrated for the polyacids poly(acrylic acid), PAA, and poly(methacrylic acid), PMAA, and for the polybases poly(vinylpyrrolidone), PVPON, and poly(ethylene oxide), PEO, in D2O. The adsorption was quantified by Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). The ratio between suppressed ionization of the carboxylic groups within the film and their ionization in solution, as directly measured by FTIR-ATR, was used to estimate the fraction of hydrogen-bonded carboxylic groups; this was ∼0.5 in PVPON/PMAA but only ∼0.1 in the PEO/PMAA system, though...

Abstract: The surfaces of nanoscale zerovalent iron (NZVI) used for groundwater remediation must be modified to be mobile in the subsurface for emplacement. Adsorbed polymers and surfactants can electrostatically, sterically, or electrosterically stabilize nanoparticle suspensions in water, but their efficacy will depend on groundwater ionic strength and cation type as well as physical and chemical heterogeneities of the aquifer material. Here, the effect of ionic strength and cation type on the mobility of bare, polymer-, and surfactant-modified NZVI is evaluated in water-saturated sand columns at low particle concentrations where filtration theory is applicable. NZVI surface modifiers include a high molecular weight (MW) (125 kg/mol) poly(methacrylic acid)-b-(methyl methacrylate)-b-(styrene sulfonate) triblock copolymer (PMAA-PMMA-PSS), polyaspartate which is a low MW (2−3 kg/mol) biopolymer, and the surfactant sodium dodecyl benzene sulfonate (SDBS, MW = 348.5 g/mol). Bare NZVI with an apparent ζ-potential of −3...

Abstract: A series of cross-linked, swellable polymers was sythesized from monomers such as acrylic acid, methacrylic acid, and others with various cross-linking agents to produce a range of polymers differing in charge densities and hydrophobicity. The densities, rate, and extent of hydration of the polymers were determined. An increase in the number of hydrophobic groups in the polymer structure reduced hydration whereas the density of the polymer was unaffected. A sensitive in vitro method for measuring adhesion of polymer to tissue from the rabbit stomach was developed. Polymers of acrylic acid loosely cross-linked (0.3%, w/w) with three different agents, divinyl glycol, 2,5-dimethyl-1,5-hexadiene, and divinylbenzene, showed the same degree of bioadhesion while poly(methacrylic acid–divinylbenzene) showed reduced bioadhesion. The small percent of cross-linking agent, irrespective of physicochemical properties, did not contribute substantially to bioadhesion, whereas the starting monomer had a large effect. The effect of pH on the bioadhesion of poly(acrylic acid–divinyl glycol) was studied at constant temperature, ionic strength, and osmolality. The polymer showed maximum adhesion at pH 5 and 6 and a minimum at pH 7. Gastrointestinal transit studies of cross-linked polymers in rats were studied. Poly(acrylic acid-divinyl glycol) and poly(methacrylic acid–divinylbenzene) were shown to have substantially longer Gl transit times than the control, Amberlite 200 resin beads. The delay in transit time was due to bioadhesion of the polymer to the mucin–epithelial cell surface which was clearly observable on animal autopsy. The acrylic acid polymer showed a longer Gl transit time than the methacrylic acid polymer, and this in vivo Gl transit result is consistent with in vitro bioadhesion test results.

Abstract: Hydrogels of an interpenetrating polymeric network (IPN) composed of the temperature-sensitive poly(N-isopropylacrylamide) (PNIPAAm) and the pH-sensitive poly(methacrylic acid) (PMAA) were prepared by a sequential UV polymerization method. The IPN hydrogels were characterized for their temperature- and pH-responsive behavior by equilibrium swelling studies, oscillatory swelling studies, and differential scanning calorimetry. The permeability of these IPNs has been investigated under various pH and temperature conditions. The results showed that these hydrogels exhibited a combined pH- and temperature-sensitivity at a temperature range of 31−32 °C and a pH value of approximately 5.5. Permeation study results indicate a significant size exclusion behavior while model drugs with different sizes permeate through the IPN membranes. The permeability of the IPN membrane can be significantly affected by varying the pH and temperature conditions.