Isothermal titration calorimetry (ITC) and UV−visible spectroscopy were used to study the supramolecular complexes of α-cyclodextrin (α-CD) and azocellulose (azobenzene functionalized hydroxypropyl methylcellulose, AZO−HPMC) in aqueous solutions. The equilibrium constant K, enthalpy change ΔH, Gibbs free energy ΔG, entropy change ΔS, and the stoichiometric number n for the inclusion complexation were determined. α-CD forms stable inclusion complexes with AZO−HPMC with the stoichiometry of 1:1. The inclusion complexation is exothermic. Both negative enthalpy and entropy changes are observed, suggesting that the inclusion complexation is enthalpy driven and entropy opposed. AZO−HPMC with higher azobenzene content (DSazo) is less favored to form inclusion complexes with α-CD due to strong H-aggregation of azobenzene groups. ITC studies confirmed that the cis azobenzene groups is unable to form an inclusion complex with α-CD. The red-shift in the absorption spectra of AZO−HPMC aqueous solution upon addition of α-CD also confirmed the formation of 1:1 complex.

The swelling behaviour and elastic properties of gelatin gels are reported. Ampholytic swelling properties have been investigated. Antipolyelectrolyte performance is observed when gels are swollen in different salt solutions. Swelling behaviour in high salt solutions is different from that in low salt solutions; this may be attributed to the formation of ion pairs. The elastic properties of the gel and their relationship with swelling character are also discussed. ©1997 SCI