Effect of Nonlinear Elasticity on the Swelling Behaviors of Highly Swollen Polyelectrolyte Gels

Abstract

Polyelectrolyte gels exhibit swelling behaviors that are dependent on the external environment. The swelling behaviors of highly charged polyelectrolyte gels can be well explained using the Flory–Rehner model combined with the Gibbs–Donnan effect and Manning’s counterion condensation effect (the FRGDM model). This study investigated the swelling properties of a series of model polyelectrolyte gels, namely tetra-polyacrylic acid-polyethylene glycol gels (Tetra-PAA-PEG gels), and determined the applicability of the FRGDM model. The swelling ratio (Vs/V0) was well reproduced by the FRGDM model in the moderate swelling regime (Vs/V0 < 10). However, in the high swelling regime (Vs/V0 > 10), the FRGDM model is approx. 1.6 times larger than the experimental results. When we introduced the finite extensibility to the elastic free energy in the FRGDM model, the swelling behavior was successfully reproduced even in the high swelling regime. Our results reveal that finite extensibility is one of the factors determining the swelling equilibrium of highly charged polyelectrolyte gels. The modified FRGDM model reproduces well the swelling behavior of a wide range of polyelectrolyte gels.

Star polymer networks: a toolbox for cross-linked polymers with controlled structure

“…The advantages of the thiol-MI reaction made it useful to construct model SPNs for the fundamental physics of hydrogels, including mechanical properties, [113][114][115][116] microscopic structure, 117 water and polymer dynamics in hydrogels, [118][119][120][121][122] and thermodynamics and swelling behavior. [123][124][125] The reaction has also been employed for various functional materials such as stimuli-responsive polymer networks [126][127][128][129][130] and ion gels. [131][132][133] Most studies have used a standard combination of 4f-PEG-SH and 4f-PEG-MI.…”

“…Here, we briefly introduce one notable example of poly(acrylic acid) (PAA)/PEG conetwork hydrogels developed by Tang and coworkers. 123,125 They synthesized 4f-PAA-MI (M n = 19 kDa) via ATRP of tert-butyl acrylate (tBA) followed by end-group modifications and hydrolysis of tert-butyl ester. 4f-PAA-MI was mixed with 4f-PEG-SH (M n = 20 kDa) at c ∼ 6 wt% in aqueous buffer solution.…”

Neutralization and Salt Effect on the Structure and Mechanical Properties of Polyacrylic Acid Gels under Equivolume Conditions

“…The polyelectrolyte gels bear dissociative ion groups in their crosslinked gel networks. The fixed dissociative ion groups on the gel networks exhibit strong Donnan potential [ 9 , 10 ], which is the origin of the high-water absorbing capability of the polyelectrolyte gels.…”