Effect of Swelling and Deswelling on Mechanical Properties of Polymer Gels

Abstract

Summary: Polymer gels exhibit some unique features that are not seen in the uncrosslinked polymer system, rubber elasticity and swelling. In this paper, we review our recent studies towards the molecular understanding of the relationship between the elasticity and the swelling ratio using the Tetra-PEG gels. The dependence of the polymer volume fraction of interest state (f m ) on the elasticity exhibits the power-law behaviors and the crossovers at f à and f c due to the presence of the excluded volume effect and the supercoiling. The Obukhov model successfully describes the power-law behaviors. The fractal dimension of network strands (D f ) based on the stress-elongation relationships using the Pincus blob revealed that the gyration radius of the network strands decreases with deswelling in affine manner. As for the equilibrium swelling, the definite f 0 -dependences of f m and E s are observed due to the effect of the excluded volume effect at preparation state. The Obukhov model can predict this result, while the C à theorem cannot predict it. Using the polymer gels with precisely controlled network structures, we successfully verify the molecular models to describe the relationships between the elasticity and the swelling degree of polymer gels.

Polyphilicity—An Extension of the Concept of Amphiphilicity in Polymers

“…Of course, polymer networks cannot be dissolved, but can only be swollen to different degrees. The swelling of polymer networks is a standard procedure to determine the polymer solubility parameters experimentally [62,63]. Poly(vinyl alcohol) is usually considered as water soluble and can also form physical polymer networks after freeze–thawing cycles of its aqueous solutions.…”

Linear viscoelastic studies on a transient network formed by host–guest interaction

“…From a theoretical point of view, the equilibrium swollen state is determined by the balance between the osmotic and elastic free energy . The osmotic free energy of polymer gels is often assumed to be described in the same manner of semi‐dilute polymer solution . Elastic free energy is determined by the equilibrium modulus, which is proportional to the number density of permanent crosslinking points.…”

“…11,12 The osmotic free energy of polymer gels is often assumed to be described in the same manner of semi-dilute polymer solution. [13][14][15][16][17][18][19] Elastic free energy is determined by the equilibrium modulus, which is proportional to the number density of permanent crosslinking points. On the contrary, temporary crosslinking points dissociate in finite time-scale, indicating that temporary crosslinkings do not contribute to the elastic free energy from the viewpoint of the thermodynamics.…”

Tunable elasticity and thermodynamic parameters of hydroxypropyl methacrylate‐based gels with varying extents of monomer concentration: Statistical mechanics treatments of physical observations

“…Recently, various theoretical works have been performed for the estimation of the formation kinetics of networks, the differences in chain rigidity and the elastic properties of stiff networks. The inhomogeneous structure of the network, cyclization and pendant chains, and initial monomer concentration have been also investigated in the chemically crosslinked gels . Although, several investigations have been carried out to understand the swelling and elasticity of acrylamide‐based Hgs, the present work is the first report for the evaluation of scaling behavior of poly(hydroxypropyl methacrylate) (PHPMA)‐based Hgs.…”

“…The inhomogeneous structure of the network, cyclization and pendant chains, and initial monomer concentration have been also investigated in the chemically crosslinked gels. [26][27][28][29] Although, several investigations have been carried out to understand the swelling and elasticity of acrylamide-based Hgs, the present work is the first report for the evaluation of scaling behavior of poly(hydroxypropyl methacrylate) (PHPMA)-based Hgs. Therefore, it is necessary to establish the scaling relationships between the physicochemical properties of a crosslinked PHPMA Hgs such as the equilibrium swelling degree, the crosslinking density, reduced modulus as well as the average network chain length and the concentration of monomers in the pre-gel mixture.…”