The surface property and aggregation behavior of a hydrophobically modified cyclodextrin

The surface property of an amphiphilic cyclodextrin 2-O-(hydroxypropyl-N,N-dimethyl-N-dodecylammonio)-beta-cyclodextrin (HPDMA-C-12-CD) was investigated using oscillating bubble rheometer and electrical conductivity method at different temperatures. The surface tension and dilational viscoelasticity of HPDMA-C-12-CD were provided. The results showed that HPDMA-C-12-CD could adsorb on the air-water interface, which decreased the surface tension of water efficiently. Critical micelle concentration (cmc) can be clearly defined from the surface tension isotherm. pC(20) and pi (cmc) were derived from the surface tension isotherms as well. The thermodynamic parameters (Delta G (0) (m) , Delta H (0) (m) , -T Delta S (0) (m)) derived from electrical conductivity indicated that the micellization of HPDMA-C-12-CD was entropy-driven at lower temperature, while it was enthalpy-driven at higher temperature. The dilational modulus appeared a maximum value while the phase angle appeared two maxima as a function of HPDMA-C-12-CD concentration.