Homogeneous grafting reaction of vinyl pyrrolidone onto chitosan

Abstract

ABSTRACT:Modification of chitosan by grafting of vinyl pyrrolidone (VP) was carried out in homogeneous phase using potassium persulfate as redox initiator. The effect of the reaction variables on the extent of grafting was studied systematically. Values for grafting percentages up to 290% were reached. It was observed that the solubility of chitosan was markedly reduced after grafting with vinyl pyrrolidone. The grafted product is insoluble in common organic solvents as well in dilute organic and inorganic acids. However, the solubility of the grafted chitosan after adsorption of copper ions changed substantially, becoming completely soluble in dilute hydrochloric acid. This was attributed to the effect of complex formation produced by coordination of amino groups of chitosan with copper ions.

Modified chitosan, 7 Graft copolymerization of methacrylonitrile onto chitosan using ammonium persulfate initiator

“…It also may be attributed to deactivation of the growing macroradical chains (e.g., by transfer reaction, combination and/or interaction with the primary radicals) soon after their formation. Similar 5 results have been reported on the grafting of acrylonitrile using Ce 4+ initiator [21] and vinylpyrrolidone using potassium persulfate initiator [14]. With increasing amount of chitosan, %Ct increased.…”

“…γ-Ray irradiation was also used to graft-copolymerize styrene, VAc and acrylamide (AAm) onto chitosan [11][12][13]. Potassium persulfate (KPS) has been used to graft poly(N-vinylpyrrolidone) [14] and poly(2-acrylamido-2-methylpropanesulfonic acid) [15] on the chitosan backbone. Acrylic acid (AA) was recently grafted onto chitosan using the KPS/ferrous ammonium sulfate initiator system [16].…”

Hydrogels based on modified chitosan, 1. Synthesis and swelling behavior of poly(acrylic acid) grafted chitosan

“…As we have previously observed, the extent of grafting vinyl monomers onto cellulose, chitin, chitosan, etc. is very sensitive towards reaction conditions 16,21,39,40) . Therefore, a systematic study of the effect of different reaction variables on grafting of acrylic acid onto chitosan, is presented in this work.…”

“…In spite of the fact that chitin is the second most abundant natural polysaccharide, its modification through grafting has not been widely explored, probably due to its insolubility in water and organic solvents. However the modification of chitosan, its principal derivative, has been carried out by grafting mainly in a heterogeneous medium and by using different catalysts [16][17][18][19][20][21][22][23][24] .…”

“…In both cases the grafted chitosan showed enhanced thermal stability 40) . Recently, by grafting vinyl pyrrolidone, we were able to carry out the reactions in a homogeneous phase 21) . The chelating capacity of chitosan grafted with polyvinylpyrrolidone for Cu 2+ ions were tested and it was found that, contrary to the case of chitosan, the complexation with Cu 2+ ions resulted in completely soluble products in dilute hydrochloric acid.…”