Polyzwitterionic Hydrogels in Engines Based on the Antipolyelectrolyte Effect and Driven by the Salinity Gradient

Abstract

In this paper, we propose and investigate an original approach to energy conversion based on polyzwitterionic hydrogels, which exhibit an antipolyelectrolyte effect that enables them to swell in salt water and shrink in water of a different (i.e., desalinated water) salinity. The swelling and shrinking processes run cyclically and can move a piston up or down reversibly, thus transforming the antipolyelectrolyte effect into a mechanical force based on the salinity gradient. This phenomenon makes polyzwitterionic hydrogels suitable for use in a smart, polymeric engine. We apply this approach to investigate energy recovery from a polysulfobetaine-based hydrogel. The cross-linking density, external load, particle size, and repeatability of energy recoverability of hydrogels are examined. The maximum energy recovery from 0.4 g of hydrogel in feed (calculated based on dry form) of 102 mJ/kg was obtained by a hydrogel with a 3% cross-linking density, a 200–300 μm particle size, and 100 g external load. Excellent reproducibility of engine cycles was achieved over 10 cycles. This concept is complementary to the osmotic engine concept based on a polyelectrolyte hydrogel. In addition, polyzwitterionic materials have become a benchmark material for preventing biofouling, and the swelling properties of such materials can be further modulated and tuned.

Influence of direct electric field on PMCG-alginate-based microcapsule

“…The change in mechanical properties can significantly influence the biocompatibility and processability of materials. Studying the effect of electrical fields and pH not only provides control and tunable material properties but also elucidates the response of microcapsules and hydrogels to electric field and pH, which can be applied in biotechnological process requiring electrochemical reaction [46], smart robotics [47], energy production [48], and water separation processes [49].…”

Recovered Energy from Salinity Gradients Utilizing Various Poly(Acrylic Acid)-Based Hydrogels

“…The alternative of using hydrogels to convert salinity gradient energy into mechanical energy has been introduced in recent years [29][30][31][32]. High and low salinity solutions alternatingly flow through a hydrogel, which is placed in a modified syringe operating in a piston-type process.…”

“…Hydrogels have the advantage of being cheap, easier to keep, and are more controllable than membrane-based technologies. The first studied hydrogels for this application was poly(acrylic acid) [29,30]; later, poly(allylamine hydrochloride) [31] and zwitterionic polysulfobetaine [32] hydrogels have been examined. It has been found that the energy efficiency decreases with increasing particle size [29,32] and goes through a maximum as the crosslinking density [30][31][32] or external load [29][30][31] is increased.…”

“…The first studied hydrogels for this application was poly(acrylic acid) [29,30]; later, poly(allylamine hydrochloride) [31] and zwitterionic polysulfobetaine [32] hydrogels have been examined. It has been found that the energy efficiency decreases with increasing particle size [29,32] and goes through a maximum as the crosslinking density [30][31][32] or external load [29][30][31] is increased. At high external loads, the recovered energy decreases for hydrogels with many charged groups [30] or low crosslinking densities [30,31].…”

Electrochemical Investigation of Interfacial Properties of Ti3C2Tx MXene Modified by Aryldiazonium Betaine Derivatives

“…Betaines as derivatives with a zwitterionic nature are named according to their negatively charged moieties such as carboxybetaine, sulfobetaine, and phosphobetaine covalently linked to positively charged quaternary ammonium moieties within one molecule. Modification with such derivatives has been utilized widely by others and by us in order to improve performance and operational parameters of biosensors (Bertok et al, 2013 , 2015 ), for protein stabilization (Kasák et al, 2016 ; Liu and Jiang, 2016 ), to develop blood-compatible materials (Chocholova et al, 2018 ) and for other advanced applications (Ilčíková et al, 2015 ; Zavahir et al, 2019 ).…”