Network structure and swelling behavior of poly(acrylamide/crotonic acid) hydrogels in aqueous salt solutions

Abstract

Hydrogels with various ionic group contents were prepared from acrylamide and crotonic acid (CrA) monomers with 0 -12.9 mol % CrA in aqueous solutions by radiation-induced polymerization and gelation with ␥ rays from a 60 Co source. The volume swelling ratio of the poly(acrylamide/crotonic acid) hydrogels was investigated as a function of the pH and ionic strength of the swelling medium and the type of counterion in the swelling medium. The volume swelling ratio increased with an increase in pH and a decrease in the ionic strength. The volume swelling ratio of these hydrogels was evaluated with an equation, based on the Flory-Huggins thermodynamic theory, the James-Guth phantom network theory, and the Donnan theory of swelling of weakly charged ionic gels, that was modified here for the determination of the molecular weight between crosslinks (M c ) and the polymer-solvent interaction parameter (). The modified equation described very well the swelling behavior of the charged polymeric network. The same equation also provided the simultaneous measurement of these parameters for the systems investigated.

Swelling Behavior of Chemically Ion‐Doped Hydrogels

“…This difference is due to the entrapped charges in DG. [27][28][29] The mass ratios of NG and BG are compared in Figure 3 for varying AAm and pyranine concentrations. The results from Figure 3 can be summarized as follows: (Figure 3a), (ii) for 0.5 and 1 M PAAm gels both the final mass ratios and the swelling rates in the initial periods increase with increasing pyranine concentration (Figure 3c and d), (iii) for 2 M gel, the final mass ratio and the swelling rates in the initial period increase again with increasing pyranine concentration (Figure 3b).…”

“…In addition, the effects of free ionic groups on the swelling behavior of the hydrogels have been studied. [27][28][29] It has been shown that the gels containing free ions undergo discontinuous transition during swelling, depending on the ionic group concentration.…”

Modeling Investigation of Hydrogel Volume Transition

“…The osmotic pressure originates from the electrostatically confined ions inside the hydrogel and the repulsive electrostatic interactions between the charged groups. Based on Equation (1) and (7) as well as the phantom network model, Caykara et al derived the following equation for predicting the equilibrium swelling behavior of copolymeric hydrogels containing monoprotic acid moieties: [24] K a 10 ÀpH þ K a…”

Synthesis and properties of methacrylic acid based hydrogels modified with zeolites

“…Opisano ponašanje anjonskih i katjonskih hidrogelova prikazano je na Slici 1.2. Hidrogelovi koji poseduju i anjonske i katjonske bočne grupe bubre na vrlo visokim i vrlo niskim pH, kada dolazi do jonizacije grupa koje ulaze u njihov sastav [40,43,44,45]. [9].…”

“…F je faktor čija je vrednost 1 za afine, odnosno 1-2/f za fantomske mreže, pri čemu je f funkcionalnost umreživača. Za nabubrele hidrogelove je utvrđeno da su bliži fantomskom modelu mreže u kom se lanci smatraju nematerijalnim ili fantomskim i mogu slobodno međusobno da se preplidu [44,101].…”