Tunable Viscoelastic Properties of Sodium Polyacrylate Solution via CO2-Responsive Switchable Water

Abstract

Upon stimulus by CO2, CO2-switchable viscoelastic fluids experience a deliberate transition between non-viscous and highly viscous solution states. Despite attracting considerable recent attention, most such fluids have not been applied at a large- scale due to their high costs and/or complex synthesis processes. Here, we report the development of CO2-switchable viscoelastic fluids using commercially available sodium polyacrylate (NaPAA) and N,N-dimethyl ethanol amine (DMEA)-based switchable water. Upon bubbling CO2, into the solutions under study, DMEA molecules are protonated to generate quaternary ammonium salts, resulting in pronounced decreases in solutions viscosity and elasticity due to the influence of increased ionic strength on NaPAA molecular conformations. Upon removal of CO2 via introduction of N2, quaternary salts are deprotonated to tertiary amines, allowing recovery of fluid viscosity and elasticity to near the initial state. This work provides a simple approach to fabricating CO2-switchable viscoelastic fluids, widening the potential use of CO2 in stimuli-responsive applications.

Strong, thermo-reversible salogels with boronate ester bonds as thermal energy storage materials

“…S3† showing that in high frequency regime beyond the modulus crossover both storage and loss moduli continued to increase. Note that the frequency-dependent behavior of the crossover point was broadly reported for many physical gels, 9,45,46 including borax-crosslinked systems, 47,48 and often explained by heterogeneity and clustering of weak physical crosslinks, 13,49 which is likely to occur in the borax-free PVA salogels stabilized by intermolecular hydrogen bonding. Fig.…”

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