Instabilities of charged polyampholytes

Yacov Kantor*, Mehran Kardar

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We consider polymers formed from a (quenched) random sequence of charged monomers of opposite signs. Such polymers, known as polyampholytes (PA's), are compact when completely neutral and expanded when highly charged. We examine the transition between the two regimes by Monte Carlo simulations, and by analogies to charged drops. We find that the overall excess charge Q is the main determinant of the size of the PA's. A polymer composed of N charges of ±q0 is compact for Q<Qcq0/N and expanded otherwise. The transition is reminiscent of the Rayleigh shape instability of a charged drop. A uniform excess charge causes the breakup of a fluid drop. We speculate that a uniformly charged polymer stretches out to a necklace shape. The inhomogeneities in charge distort the shape away from an ordered necklace.

Original languageEnglish
Pages (from-to)1299-1312
Number of pages14
JournalPhysical Review E
Issue number2
StatePublished - 1995


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