MODIFICATION OF SOME NATURAL POLYMERS BY GRAFTING WITH VINYL MONOMERS

Abstract

In the present work, chitosan is grafted with three different vinyl monomers namely 4-vinylpyridine, vinyl acetate or Acryloylcyano­ acetohydrazide (ACAH). Polyvinyl pyridine could be grafted onto chitosan up to 130 % under homogeneous conditions (in 5 % acetic acid) and up to 96 % in the heterogeneous conditions (as suspension in water). The grafting efficiency in homogeneous conditions is higher than that in heterogeneous conditions for all the investigated parameters. It was possible to control the extent of grafting by varying the reaction parameters namely, monomer concentration, initiator concentration, temperature and time. The grafted samples are insoluble in common solvents, however are soluble in hot diluted acids, therefore one can exclude crosslinking reaction between the chains but an increased hydrogen bonding making the solubility more difficult. Dye uptake of the grafted samples was studied using acidic and basic dyes. It has been shown that the acid dye uptake is much higher than that for the basic dye which is due to the basic character of chitosan and the presence of vinyl