Conformational study on the thermal transition of chitosan-g-poly(N-vinylcaprolactam) in aqueous solution
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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.
KeywordsChitosan-g-poly(N-vinylcaprolactam) Conformational transition Dynamic light scattering ζ-potential Ionic strength and pH effect
D. F.-Q. acknowledges CONACyT for his scholarship for PhD studies (325951) and to the Institute of Polymer Science and Technology (ICTP) of the Spanish National Research Council (CSIC) in Madrid, Spain, especially the Biomaterials Group. Authors thank CIBER-BBN for financial support.
Conflict of interest
The authors declare that they have no conflict of interest.
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