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)-β-cyclodextrin (HPDMA-C12-CD) was investigated using oscillating bubble rheometer and electrical conductivity method at different temperatures. The surface tension and dilational viscoelasticity of HPDMA-C12-CD were provided. The results showed that HPDMA-C12-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. pC20 and π cmc were derived from the surface tension isotherms as well. The thermodynamic parameters (ΔG 0 m , ΔH 0 m , −TΔS 0 m) derived from electrical conductivity indicated that the micellization of HPDMA-C12-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-C12-CD concentration.