Polymer chain collapse induced by many-body dipole correlations

Abstract

We present a simple analytical theory of a flexible polymer chain dissolved in a good solvent, carrying permanent freely oriented dipoles on the monomers. We take into account the dipole correlations within the random phase approximation (RPA), as well as a dielectric heterogeneity in the internal polymer volume relative to the bulk solution. We demonstrate that the dipole correlations of monomers can be taken into account as pairwise ones only when the polymer chain is in a coil conformation. In this case the dipole correlations manifest themselves through the Keesom interactions of the permanent dipoles. On the other hand, the dielectric heterogeneity effect (dielectric mismatch effect) leads to the effective interaction between the monomers of the polymeric coil. Both of these effects can be taken into account by renormalizing the second virial coefficient of the monomer-monomer volume interactions. We establish that in the case when the solvent dielectric permittivity exceeds the dielectric permittivity of the polymeric material, the dielectric mismatch effect competes with the dipole attractive interactions, leading to polymer coil expansion. In the opposite case, both the dielectric mismatch effect and the dipole attractive interaction lead to the polymer coil collapse. We analyse the coil-globule transition caused by the dipole correlations of monomers within the many-body theory. We demonstrate that accounting for the dipole correlations higher than the pairwise ones smooths this pure electrostatics driven coil-globule transition of the polymer chain.

Aggregation of flexible polyelectrolytes: Phase diagram and dynamics

“…In the dilute limit of a single PE chain in isolation, the effective attractive interactions can result in extended, bead-necklace, and collapsed conformations depending on the charge density of PE chain and temperature of the system. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] a) Electronic mail: anvym@imsc.res.in b) Electronic mail: rrajesh@imsc.res.in c) Electronic mail: vani@imsc.res.in At finite densities of PE chains, the effective attractive interactions among the PE chains can lead to aggregation, in addition to individual collapsed phases. Understanding counterion mediated aggregation of charged polymers is very relevant as the aggregation of biopolymers such as DNA and actin has been implicated to play an important role in biological functions such as cell scaffolding, DNA packaging, cytoskeletal organization [42][43][44][45][46][47][48][49] .…”

The Structure of Dipolar Polymer Brushes and Their Interaction in the Melt. Impact of Chain Stiffness

“…The answer to this question is one of the goals of the present work. It should be mentioned the theoretical works where dipolar brushes in polar solvent [20][21][22][23] were considered. In contrast to our case the directions of dipoles in the grafted chains were not correlated with the directions of monomer units.…”

“…Such macromolecules and brushes made of such grafted macromolecules are not type A systems, which are considered in our work. Kumar et al [20], Mahalik et al [21], Budkov et al [22], Gordievskaya et al [23], show that the effect of dipole-dipole interaction between transverse dipoles can be described by the introduction of the macroscopic effective Flory-Huggins-like parameter which depends on the polymer concentration. These interactions can lead to the collapse of the dipolar flat brushes and to an attraction between two opposite brushes at intermediate separation distances [24].…”

Molecular theory of the electrostatic collapse of dipolar polymer gels

“…Among them are ionomers 27 , dielectric elastomers 28 , zwitterionic polymers 29 , polymeric ionic liquids 30 , to name a few. One of the brightest effects driven by dipole-dipole interactions is the CG transition of a single dipolar polymer chain 31 . The latter can occur in polyelectrolyte solutions with low-polar solvents [32][33][34] , where the monomer units and counterions form ionic pairs, as well as in dilute solutions of polyzwitterionic macromolecules (betaines), where the monomer units carry two oppositely charged ionic groups 35 .…”

“…( 7)). Note that we have discussed this limiting regime earlier in the context of conformational behavior of a single dipolar polymer chain with point-like dipoles on its monomer units 31 . However, for the polymer chains with γ ∼ 1, the connectivity effect on the electrostatic free energy becomes considerable.…”