Microgels composed of polymeric β-cyclodextrin and polysorbates

Microgels were prepared by taking advantage of an interaction between polysorbates (PSs) and polymeric β cyclodextrin (PβCD). PSs (PS 20, PS 40, PS 60, and PS 80) were added to aqueous solutions of PβCD so that the molar ratio of PS to βCD residue was about 2:1. On FT-IR spectra, the signals of ester bonds of PSs contained in the microgels were weaker than those of ester bonds in free PSs, and the peak at 1109 cm- 1, corresponding to the –C–O–C functionality of PEO segments of PSs, also decreased in intensity, indicating that both could interact with PβCD, possibly with the βCD cavities. The mean diameters of microgels composed of PβCD/PS 20, PβCD/PS 40, PβCD/PS 60, and PβCD/PS 80 were approximately 0.1, 3.4, 7.3 and 0.05 μm, respectively. The result that the microgels of PβCD/PS 40 and PβCD/PS 60 were much larger is possibly because the tails of PS 40 and PS 60 are longer so that more βCD can be cross-linked, but for PS 80 the tail is gauche and, therefore, does not fit well into βCD cavities. The size data were in agreement with the microgels observed on microphotographs. The air/water interfacial activities of PS 40 solutions including PβCD were markedly less than those of the surfactant solutions without PβCD, indicating that it was bound to PβCD.