Attraction between Opposing Planar Dipolar Polymer Brushes

Abstract

We use a field theory approach to study the effects of permanent dipoles on interpenetration and free energy changes as a function of distance between two identical planar polymer brushes. Melts (i.e., solvent-free) and solvated brushes made up of polymers grafted on nonadsorbing substrates are studied. In particular, the weak coupling limit of the dipolar interactions is considered, which leads to concentration-dependent pairwise interactions, and the effects of orientational order are neglected. It is predicted that a gradual increase in the dipole moment of the polymer segments can lead to attractive interactions between the brushes at intermediate separation distances. Because classical theory of polymer brushes based on the strong stretching limit (SSL) and the standard self-consistent field theory (SCFT) simulations using the Flory's χ parameter always predicts repulsive interactions at all separations, our work highlights the importance of dipolar interactions in tailoring and accurately predicting forces between polar polymeric interfaces in contact with each other.

Surface Tension of Dielectric–Air Interfaces

“…Explicitly, ϵ l = 1 + 4 πl Bo p 2 ρ b /3, where l Bo = e 2 /4 πϵ o k B T is the Bjerrum length in the vacuum characterized by its permittivity ϵ o , electronic charge, e , and the Boltzmann constant, k B . In eq , the term proportional to the volume V is related to self-energy of dipoles and interactions among the dipoles. , In particular, free energy density , f b becomes directly proportional to the self-energy of dipoles in the limit when the number density of dipoles (ρ b ) vanishes i.e., ρ b → 0 e.g., for a dipolar gas. The logarithmic term appearing in the expression for f b results from multibody interactions among the dipoles and is plotted in Figure (a).…”

Fully Bio-Based and Supertough PLA Blends via a Novel Interlocking Strategy Combining Strong Dipolar Interactions and Stereocomplexation

“…However, forming these special interactions usually requires complicated chemical synthesis and processing steps to introduce specific functional groups such as hydroxyl groups into polymer chains. , Recently, strong interchain van der Waals interaction (VDW) has emerged as a promising tool to fabricate novel polymer materials with excellent performances. − Using the key-and-lock interchain junction mechanism formed by favorable interchain van der Waals forces, Urban et al reported the commodity copolymers such as PMMA/ n -butyl acrylate [P­(MMA/ n BA)], and their derivatives exhibited interesting self-healing performance. Compared to the supramolecular interaction, the strong van der Waals interaction such as dipolar interaction was more easily fulfilled in the commodity polymer without complicated chemical and physical alterations. − …”

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

“…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]. To avoid misunderstandings, A-type brushes were not considered in these works.…”