Kinetics of water flow through a polymer gel

Abstract

The water flow through the poly(acrylamide) gel under a constant water pressure is measured by newly designed apparatus. The Young modulus and Poisson's ratio of the rod shape gels are measured by the uni-axial elongation experiments, which determine the longitudinal modulus independently from the water flow experiments. The time evolution of the water flow in the dilute gel is calculated based on the collective diffusion model of the polymer network coupled with the friction between the polymer network and the water. The calculated results are compared with the time evolution of the flow experiments, and the values of the longitudinal modulus and the friction coefficient are estimated. The estimated values are consistent with the results of our mechanical-response experiments and the light scattering experiments reported previously. We find that the time evolution of the water flow is well described by a single characteristic relaxation time predicted by our model for dilute gels.

Erratum to: Hydrodynamic dispersion in $ \beta$ -lactoglobulin gels measured by PGSE NMR

“…Despite the significance, the solvent flow process inside gels has yet to be studied in detail [16]. In this study we demonstrate the ability of NMR to characterize the system dynamics non-destructively.…”

“…Advective transport of solvent through gel networks has been studied [13,16,34], these studies show that the network infers hydrodynamic friction as well as deforming from its initial configuration by the drag force, with the flow process being determined by the balance between the viscoelastic response of the gel network and the solvent flow. In investigating convective transport through gels this viscoelastic network response adds complexity relative to studies of rigid or purely elastic porous media.…”

“…The application of pulsed gradient spin echo (PGSE) nuclear magnetic resonance (NMR) [33] to measure the displacement length and time scale dependent dynamics demonstrates the applicability of the theory of hydrodynamic dispersion in porous media to analyze flow in gels. This represents a significant extension over current analysis of advective transport in gels which have focused on measurements of hydrodynamic permeability assuming classic D'Arcy law velocity scaling with pressure drop [13,16,34].…”

“…These different categories are a symptom of the diversity of gel architecture which not only depends on the constituent macromolecules but also the gelation process, where variables such as pH, ionic strength, temperature, solvent and copolymers can cause drastically different morphologies. Previous studies [9][10][11][12][13][14][15][16] have focused on understanding the fundamental correlation between the structure of gels and the dynamic properties of the constituent macromolecules and solvent. Gels generally consist of macromolecular networks with a large amount of solvent causing a large average mesh size [17] (ξ) of the network compared with the size (R) of solvent molecules (or tracers), allowing for a relatively un-restricted diffusive motion of these molecules [9,10,18].…”

Mechano-actuated ultrafast full-colour switching in layered photonic hydrogels

“…For example, considering a chemical hydrogel with m ¼ 1 kPa, Z ¼ 10 À 3 Pa s (water), the viscoelastic relaxation time t v ¼ 10 À 6 s. So chemically crosslinked gels may have fast mechanical response. The poroelasticity is associated with the solvent flow in gels and its relaxation time (t p ) is related to the characteristic size of the gel (d) and collective diffusion coefficient of the polymer network (D c ) by Suzuki et al 21 Inspired by a, this work develops a photonic hydrogel, which contains alternative stacking of rigid polymerized-DGI bilayer domains in the soft, chemically crosslinked hydrogel from hydrolyzed (h)-PAAm. The rigid bilayer domains with inter-bilayer distance of 150-250 nm, acting as 'reflective platelets', selectively diffract visible light by interference, and the h-PAAm gel layers are quasi-elastic and deform rapidly in response to the applied stress.…”