Controlling interactions at the supramolecular level is of importance for the preparation by template directed synthesis of mesoporous materials with tailored pore structures. Herein we investigate the effect of randomly methylated beta-cyclodextrin on the association behavior of the amphiphilic triblock copolymer Pluronic P123 in aqueous solution. Surface tension, dynamic light scattering, and viscosity measurements provide quantitative evidence that, when the cyclodextrin is added in controlled amounts to the copolymer, it strongly impacts the micellar growth rate. The property of randomly methylated beta-cyclodextrin to act as a micelle expander has been further exploited to generate a series of mesoporous gamma-alumina by a sol-gel method. The resulting materials subjected to calcination at 500 degrees C exhibit high surface area (354-382 m(2)/g), tunable pore size (14.8-19.3 nm), and very large pore volume (1.37-1.97 cm(3)/g), making them excellent candidates for applications in the fields of adsorption and heterogeneous catalysis.