Intramolecular phase separation of copolymer “bottle brushes”: No sharp phase transition but a tunable length scale

Abstract

A lattice model for a symmetrical copolymer "bottle brush" molecule, where two types (A,B) of flexible side chains are grafted with one chain end to a rigid backbone, is studied by a variant of the pruned-enriched Rosenbluth method (PERM), allowing for simultaneous growth of all side chains in the Monte Carlo sampling. Choosing repulsive binary interactions between unlike monomers and varying the solvent quality, it is found that phase separation into an A-rich part of the cylindrical molecule and a B-rich part can occur only locally. Long range order (in the direction of the backbone) does not occur, and hence the transition from the randomly mixed state of the bottle brush to the phase separated structure is strongly rounded, in contrast to corresponding mean field predictions. This lack of a phase transition can be understood from an analogy with spin models in one space dimension. We predict that the range of microphase separation along the bottle brush backbone can be controlled on the nanoscale by varying the solvent quality.

Tension Amplification in Tethered Layers of Bottle-Brush Polymers

“…27 Further, multicomponent brushes have been studied as potential routes to Janus particles and Janus-type polymers, resulting in an increasing number of studies of bottle-brush polymers. 14,28–34 …”

“…28,29,31,33 The current work seeks to study multiple bottle-brushes with a significant density of moderately long side chains (50–200 units) grafted to backbones with lengths from 50 to 200 monomeric units in order to examine a broader class of bottle-brush polymers. To the best of our knowledge, this represents the first simulation study directed toward refining and complementing the existing theory regarding tension accumulation in dense bottle-brush tethered layers while offering more detailed information regarding the changes in chain conformations that give rise to backbone tension accumulation and amplification.…”

Molecular Dynamics Simulations of Bottle-Brush Polymers with a Flexible Backbone under Theta and Good Solvent Conditions

“…Therefore, it has recently been shown that the persistence length depends not onlyon the backbone length [19,20], but on the solvent conditions as well [15]. Although there exist many experimental and theoretical studies for the linear d imensions of these macro molecules in various solvents [3,4,19,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36],there are very few systematic studies of this problem [15], wherethe power laws and the associated effective exponents have been with a Flexible Backbone under Theta and Good Solvent Conditions discussed.It has been shown that for bottle brushes with a flexib le backbone evenat the theta point the side chains are considerably stretched,their linear dimension depending on the solvent quality only weakly, whilethe dependence of the persistence length on backbone length and temperature has alsobeen discussed [15].…”

Simulation of Copolymer Bottle‐Brushes

“…[28] The problem of phase separation within a simple copolymer bottle-brush has also drawn attention both by analytical theory [29] and computer simulation. [30,31] In Ref., [29,30] authors gave the predictions of how the phase transition point from the randomly mixed state (where both A and B monomers are homogeneously distributed in the cylinder volume) to the separated state depends on the chain length N of the side chains and also suggested the possibility to create ''Janus cylinders'' (upper half of the cylinder containing the A monomers, lower half containing the B monomers). Recently, Hsu et.…”

“…al. [31] reconsidered this problem noting that for any finite chain length N also the cylinder radius (or brush ''height'') h is finite, and hence the system is quasione-dimensional. In one-dimensional systems with short range interactions at nonzero temperatures no long range order is possible.…”