Elasticity of single polyelectrolyte chains and their desorption
from solid supports studied by AFM based single molecule force
spectroscopy
Macromolecules, (2001)Abstract
AFM based single molecule force spectroscopy was used for the investigation
of single polyelectrolyte chains. Namely, the elasticity of polyvinylamine
chains and their desorption from solid surfaces was studied as a
function of the polymer's charge density and electrolyte concentration.
Experimental force-distance profiles were fitted by the wormlike
chain model, including elastic contributions arising from the stretching
of bond angles and covalent bonds. It was found that, under the high
stretching forces which can be applied in the AFM experiments, the
bending rigidity of polyelectrolyte chains (as described by the persistence
length) is significantly lower than predicted by Odijk-Skolnick-Fixman
(OSF) theory. Furthermore, the desorption force of single physisorbed
polymer chains from negatively charged silica surfaces was determined.
In addition to the electrostatic interaction between polymer and
substrate, which depends linearly on the Debye screening length and
the polymer's line charge density, a constant nonelectrostatic contribution
to the desorption force was observed.