Calcium Induced Volume Transition in Polyelectrolyte Gels
نویسندگان
چکیده
The osmotic properties and the small angle neutron scattering (SANS) behaviour of fully neutralized sodium polyacrylate gels are investigated in the presence of calcium ions. Analysis of the SANS response displays three characteristic length scales, two of which are of thermodynamic origin, while the third, associated with the frozen-in structural inhomogeneities, is static. The SANS results are consistent with direct osmotic observations which indicate that the thermodynamic properties cannot be adequately described by a single correlation length. The concentration dependence of the osmotic pressure displays a power law behaviour with an exponent that decreases with increasing calcium concentration.
منابع مشابه
Salt-Induced Swelling and Volume Phase Transition of Polyelectrolyte Gels
A theoretical model of polyelectrolyte gels is presented to study continuous and discontinuous volume phase transitions induced by changing salt concentration in the external solution. Phase diagrams are constructed in terms of the polymer–solvent interaction parameters, external salt concentration, and concentration of fixed charges. Comparisons with previous experiments for an ionized acrylam...
متن کاملIon- and pH-dependent volume transitions in biopolymer gels
for an Invited Paper for the MAR08 Meeting of The American Physical Society Ionand pH-dependent volume transitions in biopolymer gels FERENCE HORKAY, Laboratory of Integrative and Medical Biophysics, National Institutes of Health Swelling and collapse of polyelectrolyte gels are the result of a balance of different interactions that control the osmotic pressure and network elasticity. In biopol...
متن کاملComparison between the Effect of Calcium Ions on the Osmotic Properties of Synthetic and Biopolymer Gels
Introduction Gels are particularly suitable to study ion-polymer interactions. Monovalent-divalent cation-exchange plays central role in various physiological processes such as nerve excitation and muscle contraction It is natural to use synthetic polyelectrolyte gels as model systems to demonstrate principles, develop and verify new experimental approaches. They are relatively easy to make, th...
متن کاملIonic and pH effects on the osmotic properties and structure of polyelectrolyte gels.
We investigate the effects of salt concentration and pH on neutralized poly(acrylic acid) (PAA) gels in near physiological salt solutions. Either adding calcium ions or decreasing the pH are found to induce reversible volume transitions but the nature of these transitions seems to be different. For example, the osmotic pressure exhibits a simple power law dependence on the concentration as the ...
متن کاملEffect of calcium/sodium ion exchange on the osmotic properties and structure of polyelectrolyte gels.
We discuss the main findings of a long-term research program exploring the consequences of sodium/calcium ion exchange on the macroscopic osmotic and elastic properties, and the microscopic structure of representative synthetic polyelectrolyte (sodium polyacrylate, (polyacrylic acid)) and biopolymer gels (DNA). A common feature of these gels is that above a threshold calcium ion concentration, ...
متن کامل