Thermodynamics on inclusion complexation of b-cyclodextrin (b-CD) with n-alkylpyridinium chlorides (CnPC, n = 12, 14, 16) were measured by conductivity technique to evaluate the effects of chain length of CnPC and temperature. The data obtained indicate that inclusion complexes S(CD) and S(CD)2 had formed between surfactant and b-CD in aqueous solution. Investigation showed that the K1 (first equilibrium constant) for S(CD) formation is greater than K2 (second equilibrium constant) for S(CD)2 formation. It has been found that C12PC forms only the 1:1 complex, while C14PC and C16PC form 1:1 and 1:2 complexes. Thermodynamic parameters of the complexation, i.e. DG, DH and DS have been also calculated. The large values of DG indicate that complexation between surfactant and b-CD is very favorable.
