Abstract
Hydrogels of dimethylaminoethyl acrylate methyl chloride quaternary salt (Q9) have been synthesized with different monomer ratio by copolymerization of this poorly studied monomer either with acrylic acid or with 2-methylene bu-tane-1,4-dioic acid. Hydrogel swelling was measured as a function of the composition of the hydrogel and of the crosslinking agent ratio. High values of swelling have been obtained at very high crosslinking values (< 14 wt %) and the equilibrium swelling was reached at very low time (less than 15 minutes). The swelling isotherms consisted of a steep initial portion and then levelled off as asymptotically to the equilibrium swelling limit. The experimental data suggest clearly that the swelling process obeys second-order kinetics. According to this, the kinetics rate constant and the equilibrium water content were determined at different comonomer composition and crosslinker concentration. The calculated kinetic constants ranged from 0.48 to 3.76 × 10-2 min-1 for poly (acrylic acid-co-Q9) hydrogels and from 0.68 to 4.0 × 10-2 min-1 for poly (2-methylene butane-1,4-dioic acid-co-Q9) hydrogels depending on the hydrogels composition. The diffusion process was evaluated for each hydrogel showing a non-Fickian type diffusion. In all cases was observed a considerable increase in diffusion coefficient as Q9 content increases.
Highlights
A gel is a polymer network which swell when immersed in solvent, but which is prevented from dissolving by the presence of crosslinks which hold the structure intact
The calculated kinetic constants ranged from 0.48 to 3.76 × 10-2 min-1 for poly hydrogels and from 0.68 to 4.0 × 10-2 min-1 for poly (2-methylene butane-1,4-dioic acid-co-Q9) hydrogels depending on the hydrogels composition
An increase in the crosslinking agent ratio had as expected a decrease in the amount of swelling
Summary
A gel is a polymer network which swell when immersed in solvent, but which is prevented from dissolving by the presence of crosslinks which hold the structure intact. Gels which swell in aqueous solvents are called hydrogels [1,2]. Increasing the crosslinking agent density is a way to improve the mechanical properties but this affects adversely the swelling. Copolymerization of hydrophilic monomer (which favors swelling) with a less hydrophilic monomer results in a hydrogel with good water absorbance and improved mechanical properties in the resulting hydrogel [4]. Swelling Properties of New Hydrogels Based on the Dimethyl Amino Ethyl Acrylate Methyl Chloride. Its soft consistence could be a handicap to manipulate these polymers For those reasons Q9 was copolymerized with others common and less hydrophilic monomers 7], acrylic acid and methylenesuccinic, to improve its mechanical properties. The influence of the hydrogel composition and the crosslinking agent on the swelling behavior of these hydrogels is reported here.
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