Modified chitosan. II. H‐chitoPAN, a novel pH‐responsive superabsorbent hydrogel

Abstract

ABSTRACT:Chitosan was modified with polyacrylonitrile (PAN) through ceric-initiated graft copolymerization. The chitosan-g-PAN product was saponified using sodium hydroxide aqueous solution to prepare a novel superabsorbent hydrogel, H-chitoPAN. Duration of completing the saponification reaction as well as the water absorbency capacity of the hydrogel was decreased with increasing the alkaline concentration. Either chitosan-g-PAN or H-chito-PAN was characterized by FTIR spectroscopy and DSC, TGA, and DTG thermal methods. According to FTIR, all the nitrile groups were converted to carboxylate and carboxamide groups. Both modified chitosans exhibited enhanced thermal stability over chitosan. The H-chitoPAN superabsorbent hydrogel was recognized to be highly responsive to pH. Study of net effect of H ϩ /OH Ϫ concentration (in absent of buffer solution) showed several sharp and large volume changes vs small pH variation in the range of 2-13. This abrupt swelling behavior was explained based on variety of pH-dependent interactions of functional groups incorporated in the gel network by an external pH modulation.

Preparation and characteristics of nanosilver composite based on chitosan-graft-acrylic acid copolymer

“…Experimental evidences of this mechanism are given in the cited publication. Authors also show the possibility of ring opening reaction [31,32].…”

Gum ghatti based novel electrically conductive biomaterials: A study of conductivity and surface morphology

“…Furthermore, an increase in the reaction temperature lead to degradation of the carbon chain by sulphate radicals generated due to the decomposition of APS. The decomposition of APS also gave O 2 radical scavenger which reacted with free radicals which lead to less hydrogel formation [42]. Additionally high temperature also leads to the fastest chain termination and chain transfer reactions.…”

A convenient one‐step preparation of chitosan‐poly(sodium acrylate‐co‐acrylamide) hydrogel hybrids with super‐swelling properties

“…These parameters were chosen according to previous works. 8,9 In general, chitosan (0.50 g) was dissolved in 2 wt % acetic acid (50 mL), and the solution was stirred for 20 min to complete dissolving. The chitosan solution was precipitated using NaOH (1N) solution.…”

“…Recently, an ampholytic hydrogel has been prepared through alkaline hydrolysis of chitosan-g-PAN copolymer. 8 The hydrogel formation was based on early reports of Fanta et al 10,11 published in 1982, demonstrated that PAN can simultaneously and be saponified crosslinked in aqueous alkali in the presence of starch to produce gel. In fact, crosslinks could be formed between the alkoxide ions of starch and the nitrile groups of PAN.…”

“…Anionic hydrogels can be obtained by saponification of poly(acrylonitrile) (PAN)-grafted starch 7 and chitosan. 8,9 Chitosan, a basic polysaccharide, comprises amine (NH 2 ) groups on its backbone. Recently, an ampholytic hydrogel has been prepared through alkaline hydrolysis of chitosan-g-PAN copolymer.…”