Preparation of alkylated chitosan-based polyelectrolyte hydrogels: The effect of monomer charge on polymerization

The objective of this work was to study the effect of the loading of monomers (cationic, anionic and ampholytes) in the preparation of polyelectrolyte hydrogels (PEHG) based on alkylated vinylated chitosan, in order to improve the understanding of the effect of ionic monomers on the polymerization of alkylated vinyl chitosan to obtain PEHGs. To achieve this, sequential synthesis of PEHGs was carried out starting from chitosan, glycidyl methacrylate (GMA) and ionic monomers: sodium 4-styrenesulfonate, [3-(methacryloylamino)propyl]dimethyl (3-sulfopropyl)ammonium hydroxide and 4-(vinylbenzyl)trimethylammonium chloride. The stages of synthesis were (a) chemical modification of the chitosan with N-(3-chloro-2-hydroxypropyl)-trimethylammonium chloride as an alkylating agent to obtain chitosan with positive charges, (b) insertion of vinyl side groups by opening the epoxide ring at pH 3.8 using GMA and (c) in situ polymerization of vinyl monomers in a polyelectrolyte aqueous solution (ACh-vinyl solution). Characterizations of the intermediate and PEHGs were performed. It was concluded that the different solution processes occurring in the reactor can be explained by counterion condensation theory in conjunction with Gibbs-Donnan equilibrium. The water absorption capacities of PEHGs were 144.6, 42.7, and 92.5 g H2O/g of dried HG for cationic, ampholyte, and anionic hydrogels, respectively.