Localized structures of polymers with long-range interactions

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Abstract
The configurational properties of a heteropolymer with prescribed sequences of known concentrations of dipolar segments are investigated. The theoretical analysis of a model chain capable of aggregation into domains shows that entropic frustrations lead to localized structures. In these structures, polymer size is determined dominantly by the formation of aggregates and not by the chain length. This localization effect occurs in addition to the familiar aspects of helix-coil and coil-globule transitions. The formation of localized structures as predicted by the theory is verified by Monte Carlo simulations of heteropolymers bearing segments with dipolar interactions. The transition of a rodlike configuration into a coil can be induced in a sharp manner also by dilution of the chain backbone. The simulations show that disordered homopolymers bearing segments with dipolar or other long-ranged inverse power law interactions do not undergo any phase transition to an ordered state at nonzero temperatures. The ability of a heteropolymer with dipolar and neutral segments to form localized structures is found to be nontrivially controlled by the specificity of the sequences.