Carboxymethylated--cyclodextrin/chitosan particles: bulk solids and aqueous dispersions

Polyelectrolyte complexes (PECs) are widely used in systems for the release of drugs, fertilizers as well as in the surface modification of fibers and particles. In this work, PEC dispersions were produced from chitosan (CS), a cationic biopolymer, and an anionic cyclodextrin (carboxymethylated--cyclodextrin, CM-beta-CD, synthesized in this work), in order to obtain particles with polar regions, around the ionic crosslinking sites, and hydrophobic regions from cyclodextrin molecules internal cavities. Bulk materials were characterized by FTIR, XRD, TGA, and MALDI-TOF. PEC dispersions were additionally characterized by viscometry, zeta potential measurements, and DLS. Apart from the usual loss of crystallinity observed as PEC is formed, in the specific case of CS/CM-beta-CD complex a drastic formation of dispersed solid phase was observed, without the detection of an initial decrease of macromolecular dimensions of soluble macromolecular species. This unusual behavior was associated to the high degree of substitution of the CM-beta-CD prepared in this work.