 ISSN 0235-7216 ISSN 2424-4538 (online) |
2009 m. Nr. 2 Polyampholytes from natural building blocks: synthesis and properties of chitosan-O-alginate copolymers
Chitosan-O-alginate comb copolymers with a different degree of chitosan substitution were synthesized using chitosan protected by phthaloylation and “activated” by tosylation, and reduced low-molecular-weight sodium alginate. The obtained chitosan derivatives were characterized by FT-IR and 1H NMR spectroscopy, functional group analysis, viscometry and potentiometric titration. The novel nature-friendly polyampholytes contained a 15–25-fold excess of carboxyl groups and were soluble in neutral and alkaline water. The intrinsic viscosity and molecular weight of these chitosan derivatives were relatively low, suggesting a significant breakdown of chitosan backbone under derivatization. The solution viscosity of the polyampholytes had a tendency to decrease by lowering the pH toward a supposed isoelectric point at pH 3.5–4.0. Comb-shaped copolymers in aqueous solutions are expected to form tight coils which are stabilized by intra- and intermolecular complexes between carboxyl and amine groups. Keywords: chitosan, sodium alginate, comb copolymer, polyampholyte, nature-friendly |
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