Conductimetric and viscometric study of the macromolecular complex between poly(acrylic acid) and poly(vinyl pyrrolidone)

cited By 7International audienceThe intermacromolecular complex between poly(acrylic acid) (PAA) and poly(vinyl pyrrolidone) (PVP) was studied by means of conductimetry and viscometry. Conductimetry is shown to be a useful tool in the investigation of this kind of complex because the polyacid dissociation is suppressed in the presence of PVP. Near to stoichiometry there is a minimum in the viscosity-composition curves due to the formation of aggregates. When varying the degree of neutralization of the polyacid to values lower than 0.1 a different pattern of behavior is seen with respect to the composition of the complex, depending on which polymer has a higher degree of polymerization (PAA or PVP). On the basis of quantitative analysis of the conductimetric titration data, a relationship is proposed to evaluate the degree of complexation between both macromolecules. This parameter diminishes with increasing charge density in the PAA chain, falling to zero for values of degree of neutralization close to 0.1. © 1998 Elsevier Science Ltd. All rights reserved

Synthesis of regioselective chitosan copolymers with β-cyclodextrin and poly(N-isopropyl acrylamide)

This work aimed to design a synthetic route under mild conditions allowing the main chitosan chain to be grafted with β-cyclodextrin (β-CD) and poly(N-isopropyl acrylamide) (PNIPAm), at C2 and C6 positions, respectively. For this reason, the regioselectivity of proposed reactions is an important factor to be considered. β-CD is an oligosaccharide with a cyclic structure capable of forming inclusion complexes with hydrophobic molecules. Grafting β-CD onto the chitosan backbone by reductive N-alkylation at C2 position was carried out. With this purpose, the previous preparation of β-CD monoaldehyde was required. PNIPAm is a thermosensitive polymer with a transition temperature near 33 °C. To regioselectively anchor poly(N-isopropyl acrylamide) chains onto chitosan at C6 position, it was required to attach at the C6 position of chitosan an alkyl group for the subsequent grafting of PNIPAm-N3 by means of copper-catalyzed azide-alkyne cycloaddition click reaction. To guarantee the regioselectivity of the functionalization of chitosan with a C6 terminal alkyne, its oxyalkylation with glycidyl propargyl ether in a solvent composed of LiOH/KOH/urea was used. The structure of all derivatives was confirmed by FT-IR and 1H-NMR spectroscopy

Adsorption Behavior of Metal Ions on Cross-linked Chitosan and the Determination of Oxoanions after Pretreatment with a Chitosan Column

The adsorption behavior of 60 elements at the 10 ng ml(-1) level on high-porous cross-linked chitosan in a packed mini-column was systematically examined. The chitosan used could adsorb anionic species quantitatively as oxoanions or chloro complex anions of metals, such as Ti, V, Mo, W, Ga, Bi, Au(III), Pt(IV) and Pd(II), in sample solutions by an ion-exchange mechanism, and could adsorb some metal ions by a chelating mechanism. Most of the metal ions adsorbed on the chitosan were eluted with 1 M nitric acid, and other noble metals, such as Au, Pt and Pd, were eluted by a solution containing 1 M hydrochloric acid and 0.05 M thiourea. The adsorption fraction of metal ions was investigated by measuring metal ions in eluates by ICP-MS. By using the proposed column pretreatment method, metal ions present as their oxoanions in river-water samples, such as Ti, V, Mo, W, Ga and Bi, were collected on the cross-linked chitosan, eluted and determined. The method was applied to an analysis of reference materials distributed by the Japan Society for Analytical Chemistry: JAC 0031 and JAC 0032. The analytical results agreed closely with other reference values