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Conformational changes of the thermal transitions of chitosan- graft-poly( N-vinylcaprolactam) copolymers in aqueous solution were studied by varying of the length of the grafted poly( N-vinylcaprolactam) (PVCL) chains, as well as the ionic strength and the pH of the solution. The conformational properties of the copolymer were monitored by means of dynamic light scattering and ζ-potential measurements. A series of copolymers with defined molecular architecture were synthesized. Obtained results point out that hydrophobic hydration plays a crucial role on the solubility of this copolymer at neutral and slightly alkaline solutions. The evolution of the size of macromolecular aggregates indicates that, in the coil state, there is a monomodal distribution, passing through a bimodal distribution in the pre-transition region, just before the phase separation. The role of the charge of the copolymers on the cooperative transition is also analyzed. The phase transition of these amphiphilic copolymers shows a strong dependence on the ionic strength of the solution. [ABSTRACT FROM AUTHOR]