Structure and phase behaviour of diblock copolymer monolayers investigated by means of Monte Carlo simulation

Abstract

We use grand canonical Monte Carlo simulation paired with multiple histogram reweighting, hyperparallel tempering and finite size scaling to investigate the structure and phase behaviour of monolayers of diblock copolymers. The chain molecules are arranged on the square lattice and we consider both fully flexible and rod-coil polymer models. In contrast to the majority of previous studies we assume that the interactions between the segments belonging to one of the two subunits are weaker than the remaining segment-segment interactions. We find that when the diblock copolymer is fully flexible, this choice of the interactions leads to a suppression of the ordered phase, and the phase behaviour is analogous to that of the fully flexible homopolymer model. However, when one of the subunits is rigid, we observe the formation of a novel hairpin chessboard ordered structure with fully stretched chains bent in the middle. The topology of the phase diagram depends on the chain length. For shorter chains the global phase diagram features a critical point and a triple point. For longer chains the gas-disordered liquid phase transition is suppressed and only the order-disorder transition remains stable. The resulting phase diagram is of the swan neck type.

Density functional theory for polymeric systems in 2D

“…An extension to mixtures is fairly straightforward. A particularly interesting subject seems to be the formation of the ordered monolayers of the diblock copolymers [10,11]. Some of these issues are already under study.…”

“…Already for heteronuclear dimers the corresponding phase diagrams may involve a λ-line, two critical points or a tricritical point [8,9]. Longer, fully flexible or rod-coil lattice models of diblock copolymers were investigated by means of Monte Carlo simulation very recently [10,11]. All these studies show an intimate and complex connection between the shape of a polyatomic molecule and its phase behaviour within the adsorbed monolayer.…”

Block copolymers for supercapacitors, dielectric capacitors and batteries

“…The widely practiced synthesis methods include reversible addition fragmentation chain transfer (RAFT) polymerization [4], atom transfer radical polymerization (ATRP) [5], ring-opening metathesis polymerization (ROMP) [6], living cationic polymerization [7], and anionic polymerization [8]. A notable feature of block copolymers is their capability of self-assembly into diverse morphologies [9,10]. Because the constituent blocks are immiscible with one another, blocks of the same chemistry tend to aggregate and repel blocks of different chemistries when subjected to solvent or thermal annealing.…”