Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 17: Physics of polymers I
CPP 17.4: Vortrag
Dienstag, 8. März 2005, 10:30–10:45, TU C130
Annealed Polyelectrolytes in a Poor Solvent — •Christian Seidel and Sahin Uyaver — Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Abt. Theorie, 14476 Potsdam-Golm
In weak (so-called annealed) polyelectrolytes (PELs) the degree of charging is not fixed but can be tuned by changing the solution pH. Due to dissociation and recombination of ion pairs the charge can move along the chain. This extra degree of freedom gives rise to new and nontrivial features. In particular, for PELs in a poor solvent, the annealing of charges can have strong effects.
Using (semi-)grand canonical Monte Carlo simulations of a chain of contour length Nb we focus on the conformational properties in the close-to-Θ-point regime τ = (Θ − T)/Θ < τ* ∼ N−1/5u3/5 (u=λB/b with λB being the Bjerrum length) as well as in the deep-poor-solvent regime τ > τ*. In the latter case we find the first-order transition between a weakly charged globule and a highly charged extended chain predicted by theory [1]. For τ < τ* we demonstrate that a cascade of pearl-necklace transitions can be initiated by changing the pH [2]. This result is in fact very similar to recent experimental date [3].
[1] S. Uyaver, C. Seidel, Europhys. Lett. 64 (2003) 536.
[2] 2. Uyaver, C. Seidel, J. Phys. Chem. 108 (2004) to appear in Dec.
[3] L.J. Kirwan et al., Nano Lett. 4 (2004) 149.