Abstract
Polyelectrolyte complexes(PECs)of hyperbranched(HB)and linear polysaccharides are promising as more effective encapsulation agents compared to PECs formed by linear polysaccharides.We investigated the PECs between the HB anionic polysaccharide fucoidan(FUC)and the cationic linear polysaccharide chitosan(CS).The FUC had a molecular weight(MW)of 30×106.The PECs were prepared in three solvents(wa-ter,0.01 and 0.1 mol/L acetic acid)with CS of MW of 15,110 and 170 kDa,and deacetylation degrees(DDA)of 70％and 97％.The structures of the PECs and the initial FUC were investigated by multi-angle static and dynamic light scattering.As the FUC contained 18 wt％of-OSO3 groups and 5 wt％of uronic acid units,it was a"strong-weak"copolyanion,so the HB macromolecules of the FUC formed nanogel particles in 0.1 mol/L AcOH and open branched structures in water,as confirmed by the Kratky plots.After mixing the solutions of original components,the PEC struc-tures underwent an equilibration period,the duration of which increased with the MW of CS.As the charge stoichiometry was approached,the PECs shrank;the fractal dimension approached unity,indicating the side-by-side packing of adjacent FUC branches with the help of CS.Sec-ondary aggregation in the vicinity of the charge compensation was hardly observed,as it occurred in a very narrow region.The PEC content at theζ-potential inversion depended on solvents'pH and the DDA of CS.In the extreme case of core-shell PECs in 0.1 mol/L AcOH,obtained by mixing FUC nanogels with the solutions of high MW CS of 97％DDA,the protruding tails of CS formed a positively charged shell in the whole range of FUC content(10 wt％＜WFUC＜90 wt％).Scanning electron microscopy and atomic force microscopy images of dried samples were discussed in relation to the light scattering results.
基金项目
Russian Science Foundation()
St.-Petersburg Science Foundation(23-23-10005)
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