Binary Polymer Brush in a Solvent

Abstract

We have studied the equilibrium structure of a grafted polymer layer composed of two distinct species of homopolymers, the “binary brush”, in various solvent conditions. By using a coarse-grained simulation method that involves direct calculation of the Edwards hamiltonian, we are able to simulate much larger systems than would otherwise be possible with a more standard lattice simulation. If the two species are made sufficiently immiscible, we find lateral binary microphase separation over a wide range of solvent conditions. Due to the presence of solvent, we find a stage where the brush expands in a laterally homogeneous manner as immiscibility increases. In this stage, laterally averaged quantities are well-described by a single solvent−related parameter: a modified excluded volume parameter. This is followed by lateral microphase separation in which the brush volume remains relatively constant. In ϑ solvent, this phase separation sets in at a degree of immiscibility consistent with a mean field prediction for melt layers. The onset of phase separation is delayed as solvent quality increases. Furthermore, a reduction in solvent quality results in a stronger crossover between mixed and phase-separated configurations. Under poor solvent conditions, we find interesting structural variations as a result of the combination of phase separation from solvent and phase separation of the two species.

Preparation and characterization of V-shaped PS-b-PEO brushes anchored on planar gold substrate through the trithiocarbonate junction group

“…As a result, the surface properties of the mixed polymer brush can be tuned or switched by applying external stimuli [18][19][20][21][22][23][24][25][26][27][28][29]. Due to the interesting phase separation phenomena and the resulting smart properties of the mixed polymer brush, a substantial amount of theoretical [30][31][32][33][34][35][36][37][38][39][40][41][42] and experimental [43][44][45][46][47] work has been devoted to this field.…”

Layered structure in compatible binary polymer brushes with high graft density: A computer simulation study

“…[40][41][42] Surfaces covered by the mixed brushes can also be applied for reversible patterning of nanofluidic devices. 43 Different theoretical studies, 41,[44][45][46][47][48][49][50] simulations, [51][52][53][54][55] and experiments [56][57][58][59][60][61][62] had focused on the immiscible binary polymer brushes, most of which had taken into account the factors such as the solvent quality, graft density, chain length, and incompatibility between species. Marko and Witten 44 first used the self-consistent field theory ͑SCFT͒ to predict that a second-order phase transition would occur with the increase of incompatibility between two species in melt binary brushes.…”

Off-lattice Monte Carlo simulation of the discrete Edwards model

“…Estimates for the scaling exponents of the Domb-Joyce model are known from a field-theoretic analysis of high-precision MC data. 15,16 Recently we used discretized Edwards chains in conjunction with off-lattice Monte Carlo simulation schemes for a variety of polymer systems including grafted polymer brushes in a good solvent 17 as well as in a poor solvent, 18 binary brushes in both good and poor solvent, 19 polymer brushes in a good solvent under shear, 20 and diblock copolymer melts. 21,22 The characteristic feature of the models used in these studies is that the volume interaction is formulated as a "virial expansion" in terms of coarse-grained number densities of the effective chain monomers ("vertices").…”