Article,
Weakly charged polyelectrolytes: Collapse induced by extra ionization
Macromolecules, (1996)
Abstract
Several experimental facts indicate that the collapse transition in
weakly charged polyelectrolyte gels or single macromolecules can
take place with an increase in the degree of ionization (e.g., during
titration of a weak polyacid). This unusual behavior can be explained
by the energy gain from the formation of ion pairs in the collapsed
state of low polarity, which competes with the swollen state where
most of the counterions are dissociated. An increasing degree of
ionization increases the thermodynamic advantages of the collapsed
state with an ionomeric multiplet structure over the swollen polyelectrolyte
state. In some regimes, this effect can lead to reentrant phase transition
behavior, i.e., to an initial decollapse of the gel upon charging
with subsequent jumplike collapse at a higher fraction of charged
monomer units.
