Advertisement

Determination of mechanical parameters related to the kinetics of swelling in an electrically activated contractile gel

  • P. Chiarelli
  • D. De Rossi
Conference paper
Part of the Progress in Colloid & Polymer Science book series (PROGCOLLOID, volume 78)

Abstract

We report on an analytical model and related experiments to determine the mechanical parameters governing the kinetics of mechanical readjustment of a thermally crosslinked polyacrylic acid (20% by weight) and polyvinylalcohol (80% by weight) (PAA-PVA) gel.

Either thin films on spherical samples have been used in the experiments. The characteristic time of swelling in the case of a thin film has been found to be proportional to the square of a linear dimension of the sample divided by a diffusion coefficient D, defined as D = μ/f, where μ is the shear modulus of the gel network and f is the friction coefficient between the network and fluid.

This constitutes and essential difference between the swelling of spherical samples reported in literature in which the diffusion coefficient is D* = (k + 4/3)/f, where k is the bulk modulus of the gel network.

We have derived the value of the bulk modulus k, the shear modulus μ and the friction coefficient f by free swelling experiments performed on spherical and planar thin samples, and by direct measurement of water permeability across the gel.

Mechanical readjustment time constant and diffusion-reaction time constant, which has been previously determined, are then compared to evaluate the limiting rate phenommena which govern the kinetics of gel deswelling under electrochemical stimuli in different pH ranges.

Key words

Polyelectrolyte gels polyacrylic acid + polyvinylalcohol thermally cross-linked swelling kinetics electromechanochemistry 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    De Rossi D, Parrini P, Chiarelli P, Buzzigoli G (1985) Electrically induced contractile phenomena in charged polymer networks: preliminary study on the feasibility of muscle-like structures. Trans Am Soc Artif Int Organs XXXI: 60–65Google Scholar
  2. 2.
    De Rossi D, Domenici C, Chiarelli P (1988) In: Dario P (ed) Analogs of biological tissues for mechanoelectrical transduction: tactile sensors and muscle-like actuators, Sensors and sensory systems for advanced robots. Springer-Verlag, BerlinGoogle Scholar
  3. 3.
    De Rossi D, Chiarelli P, Buzzogoli G, Domenici C, Lazzeri L (1986) Contractile behavior of electrically activated mechanochemical polymer actuators. Trans Am Soc Artif Int Organs, vol XXXII, pp 157–162Google Scholar
  4. 4.
    Shoenfeld NA, Grodzinsky AJ (1980) Contribution of electro-diffusion to the dynamics of electrically stimulated changes in mechanical properties of collagen membranes. Biopolymers 19:241–262CrossRefGoogle Scholar
  5. 5.
    De Rossi D, Chiarelli P, Genuini G, Dynamics of electrically driven muscle-like actuators, in preparationGoogle Scholar
  6. 6.
    Nussbaum JH, Grodzinsky AJ (1981) Proton diffusion reaction in a protein polyelectrolyte membrane and the kinetics of electromechanical forces. J Membrane Science 8:193–219CrossRefGoogle Scholar
  7. 7.
    Tanaka T, Hocker LO, Benedek GB (1973) Spectrum of light scattered from a viscoelastic gel. J Chem Phys 59:5151–5159CrossRefGoogle Scholar
  8. 8.
    Johnson DL (1982) Elastodynamics of gels. J Chem Phys 77:1531–1540CrossRefGoogle Scholar
  9. 9.
    Eisemberg SR (1983) Nonequilibrium electromechanical interactions in cartilage: swelling and electrokinetics. Sc D thesis, Dep Elec Eng and Comp Science, MITGoogle Scholar
  10. 10.
    Tanaka T, Fillmore DJ (1979) Kinetics of swelling of gels. J Chem Phys 70:1214–1218CrossRefGoogle Scholar

Copyright information

© Dr. Dietrich Steinkopff Verlag GmbH & Co. KG 1998

Authors and Affiliations

  • P. Chiarelli
    • 1
  • D. De Rossi
    • 1
  1. 1.Centro “E. Piaggio” Facolta di IngegneriaUniversita di PisaPisaItaly

Personalised recommendations