Influence of macromolecules conformation of chitosan on its graft polymerization with vinyl monomers and the copolymer properties

•Conformational transition of chitosan macromolecules was identified by spectrophotometry.•Conformational transition of the chitosan macromolecules is pH and temperature-sensitive.•Copolymers of chitosan and 2-HEMA/VP were prepared and characterized.•The graft polymerization depends on chitosan macromolecules conformation. The conformational states of chitosan macromolecules in solutions and their influence on the "grafting from" polymerization of 2-hydroxyethyl methacrylate and N-vinylpyrrolidone on the polysaccharide and the properties of their copolymers are studied. The conformational transition of macromolecules coil-rigid rod and rigid rod-globule in aqueous acidic solution was established by spectrophotometric method. The coil-rigid rod conformation transition depends on pH, it is sensitive to temperature and doesn't depend on the molecular weight of chitosan. The effective size of chitosan macromolecules for the rigid rod conformation was larger than for the coil conformation. The yield of the graft copolymer was significantly higher in case of where chitosan macromolecules were in the coil conformation (96 %) than in the rigid rod conformation (81 %). In the first case, the product of synthesis is a homogeneous solution, in the second case it is a colloidal solution. The copolymers were characterized by FTIR spectroscopy and gel-permeation chromatography.