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The European Physical Journal B
ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)
Abstract Volume 1 Issue 3 (1998) pp 371-376
Multiple conformations in polyampholytes
N. Lee (a), S. Obukhov (b)
Department of Physics, University of Florida, Gainesville, FL 32611, USA
Received: 10 July 1997 / Accepted: 13 October 1997
Abstract: We study the configurational statistics of a ring polyampholyte chain made of N randomly charged monomers with elementary charge $\pm q_{\rm o}$.To a large extent, the overall structure of a polyampholyte is controlled by a total sum Q of all charges. When the total charge is smaller than $Q_1\approx \sqrt{N}q_{\rm o}$, the polyampholyte has a compact globular structure. At charges larger than $Q_2 (\sim N q_{\rm o})$, the configuration has the form of a ring of small globules (beads) connected by strings. Between Q1 and Q2 we find a remarkable diversity of meta-stable configurations having the shapes of irregular clusters of small globules connected by the strings. We estimate the number of these configurations and the energy barriers between them. Between Q1 and Q2, the minimum energy configurations are completely controlled by randomness in the charge distribution along the chain. There are hysteresis effects in the shapes of the clusters. As the total charge increases, the linearly extended configurations become dynamically more preferable. When the charge decreases, the circular shapes are preferred. We remark on the probable connection with the multiple phase transitions observed in polyampholyte gels.
PACS. 36.20.Ey Conformation (statistics and dynamics). - 36.20.-r Macromolecules and polymer molecules. - 61.25.Hq Macromolecular and polymer solutions; polymer melts; swelling
(a) Present address: IPST, University of Maryland, College Park, Maryland 20742, USA
(b) email: sergei@phys.ufl.edu
Online publication: February 24, 1998
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