Stimuli-sensitive behaviour of novel betaine-type polyampholytes (original) (raw)
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Macromolecular Symposia, 2004
Novel linear and crosslinked polybetaines based on acrylic acid (AA) and ethyl 3-aminocrotonate (CRO) have been synthesized by a Michael addition reaction followed by radical polymerization. The polymerization of AA and CRO was carried out in bulk, water and organic solvents. The dependence of polymer yield on the molar ratio of monomers and water content was found. Primary attention was paid to linear and crosslinked polybetaines synthesized at equimolar ratio of monomers in the feed. The composition and structure of linear polybetaines was determined by elemental analysis, potentiometric titration, FTIR and NMR spectroscopy. The isoelectric points of linear and crosslinked polybetaines determined by electrophoresis, viscometry and swelling experiments corresponded to pH 2.0-2.2. The stimuli-sensitive properties of amphoteric gels were studied as a function of pH, ionic strength, water-organic solvent mixture, electric, and combined electric and magnetic fields. Appearance of pH gradient within the polyampholyte gel matrix under the externally imposed DC electric field was observed.
Preparation and Characterization of Novel Polymeric Betaines Based on Aminocrotonates
Journal of Macromolecular Science, Part A, 2007
Preparation of novel poly(alkylamine)-derived hydrogels is described. Polymers are prepared via reaction of various diamines with dihalo compounds or diepoxides. N-substituted polymers are readily prepared by reaction of primary amines with dihalo compounds. The resulting covalently cross-linked polymers exhibit hydrogel behavior (high swell with water) when ionized to polyammonium species at low pH. At high pH, the polymers reside in the free base polyamine form and lose all hydrogel character (they no longer swell in water). Characterization of polymer structure with carbon-13 NMR, thermal analysis, and swell behavior reveals a structure which is highly branched and only loosely cross-linked. In the ionic polyammonium form thermal stability up to ∼300°C is observed. The polymers exhibit activity as bile acid sequestrants significantly superior to cholestyramine, as evidenced by their ability to efficiently bind quantities of cholate when tested in vitro. This behavior indicates that these hydrogels should be very useful for the treatment of hypercholesterolemia.
Phase Transition of Acrylamide‐Based Polyampholyte Gels in Water
Journal of Macromolecular Science, Part A, 2006
The swelling behavior of acrylamide (AAm)-based polyampholyte hydrogels in water and in aqueous salt (NaCl) solutions was investigated. [(Methacrylamido)propyl]trimethyl-ammonium chloride (MAPTAC) and acrylic acid (AAc) were used as the ionic comonomer in the hydrogel preparation. Three sets of hydrogels containing 70 mol% AAm and 30 mol% ionic comonomers of varying mole ratios were prepared. The variations of the hydrogel volume in response to changes in pH, and salt concentration were measured. As pH increases from 1, the hydrogel volume V eq in water first increases and reaches a maximum value at a certain pH. Then, it decreases again with a further increase in pH and attains a minimum value around the isoelectric point (IEP). After passing the collapsed plateau region, the gel reswells again up to pH ¼ 7.1. The reswelling of the collapsed gels containing 10 and 4% MAPTAC occurs as a first-order phase transition at pH ¼ 5.85 and 4.35, respectively, while the hydrogel with 1% MAPTAC reswells continuously beyond its IEP. Depending on pH of the solution, the hydrogels immersed in salt solutions exhibit typical polyelectrolyte or antipolyelectrolye behavior. The experimental swelling data were compared with the predictions of the Flory-Rehner theory of swelling equilibrium including the ideal Donnan equilibria. It was shown that the equilibrium swelling theory qualitatively predicts the experimental behavior of polyampholyte hydrogels.
Polyacrylamide-based polyampholytes and their applications
Reviews in Chemical Engineering, 2014
Polyampholytes are charged macromolecules bearing both anionic and cationic groups along the polymer backbone. Polyampholytes can be synthesized by classic and controlled free radical polymerization, anionic polymerization, and group transfer polymerization (GTP). The aqueous solution behavior of polyampholytes is dictated by columbic interactions between the basic and acidic residues. Polyampholytes show both polyelectrolyte and anti-polyelectrolyte behavior in aqueous media. Factors such as charge density, charge asymmetry (i.e., degree of charge balance), charge spacing and distribution, substrate surface charge, structural conformation, and solution ionic strength are critical parameters. Polyampholytes are interesting for numerous reasons and are used for many technology processes such as water treatment, enhanced oil recovery (EOR), sludge dewatering, papermaking, pigment retention, mineral processing, and flocculation. In the present study, the main structural features, behaviors, mechanisms of interaction, and recent field applications of polyacrylamide (PAM)-based polyampholytes are reviewed.
Colloidal effects of acrylamide polyampholytes
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006
The colloidal and electrokinetic behavior of three amphoteric acrylamide-based water-soluble terpolymers of high molecular mass was elucidated in terms of their structure and composition, using potentiometric and colloidal titrations, as well as microelectrophoresis, viscometry, and turbidity measurements. Independent variables included polymer composition, pH, and the concentration of salt ions. The electrokinetic properties, titratable charge, and isoelectric pH values of the samples were compared to their monomeric composition, as confirmed by NMR and FTIR analysis. The electrophoretic mobilities of the polyampholytes changed relatively rapidly with pH in the neighborhood of the isoelectric pH values, consistent with an enrichment of excess charges toward the outer parts of the macromolecules. Interactions of the polyampholytes with highly-charged titrants appeared to be less pH-dependent, in the neighborhood of the isoelectric condition, relative to a linear prediction based on the numbers of acidic and basic macromolecular groups. Specific viscosity measurements, in the vicinity of the isoelectric point, were found to increase with increasing salt concentration, which is a typical anti-polyelectrolyte behavior. In a similar manner, salt addition suppressed the development of a turbidity maximum at the isoelectric point.