Communication: Self-assembly of semiflexible-flexible block copolymers

Abstract

We apply the methodology of self-consistent Brownian dynamics simulations to study the selfassembly behavior in melts of semiflexible-flexible diblock copolymers as a function of the persistence length of the semiflexible block. Our results reveal a novel progression of morphologies in transitioning from the case of flexible-coil to rod-coil copolymers. At even moderate persistence lengths, the morphologies in the semiflexible-block rich region of the phase diagram transform to liquid crystalline phases. In contrast, the phases in the flexible-block rich region of the phase diagram persist up to much larger persistence lengths. Our analysis suggests that the development of orientational order in the semiflexible block to be a critical factor influencing the morphologies of self-assembly. Introduction. Recently, the self-assembly characteristics of block copolymers in which one or more of the blocks possess appreciable degree of stiffness has attracted attention in many applications.1 However, in contrast to the well-studied situation of flexible block copolymer systems, morphologies resulting from the self-assembly of semiflexible and rod-like block copolymers are relatively less understood. For instance, experiments on rod-coil block copolymers have suggested rich morphological phase behavior which includes layered smectics, arrowheads, wavy lamellae, zigzags, etc.2 An understanding of the dependencies of such morphologies upon the physicochemical characteristics of the polymers is essential for achieving fruition in the desired applications.There have been some attempts to model the selfassembly behavior of block copolymers containing semiflexible and rigid blocks. Early researches in this context used scaling arguments and/or analytical theories to clarify the self-assembly characteristics for the case in which one of the blocks was "rigid" or rod-like. 3,4 More recently, a number of researchers have also extended the numerical framework of polymer self-consistent field theory (SCFT) (Ref. 5) to address the self-assembly characteristics of such rod-coil block copolymers. 6,7 Despite such advances, modeling the self-assembly behavior of di-and multiblock copolymers containing semiflexible units remain an outstanding challenge. Specifically, in such a context, the mathematical framework of polymer SCFT requires the solution of a diffusion-like equation in the space of two-dimensional orientational vector in addition to the physical space dimensions.

Interfacial behavior of the decane + brine + surfactant system in the presence of carbon dioxide, methane, and their mixture

“…Molecular simulations have emerged as important tools for accurately predicting the bulk and interfacial properties. 9,[12][13][14]38,[59][60][61][62] Here, we perform molecular dynamics (MD) simulations to get insights into the interfacial behavior of the decane + brine + surfactant system in the presence of CH 4 and CO 2 at reservoir conditions.…”

Impact of intrinsic backbone chain stiffness on the morphologies of bottle-brush diblock copolymers

“…[6,9,10,12,16,32] In the classic phase diagram of linear diblock copolymers, the equilibrium morphology is determined by the balance between the competing block interfacial tension and the entropic penalty of stretching the polymer coils to fill the space uniformly. [1] Introducing an asymmetry in the segmental size/stiffness between the blocks, towards rod-coil copolymers, results in significant shifts of the boundaries between morphologies [19,39] at the cost of slowing down the self-assembly kinetics. [20] These shifts in the boundaries between different ordered phases are of considerable interest, as mechanical, rheological, and optical properties of the phases are highly influenced by their topology.…”

Bulk and Interfacial Properties of the Decane + Brine System in the Presence of Carbon Dioxide, Methane, and Their Mixture

“…Molecular simulations provide valuable insights into the bulk and interfacial properties of various systems [14][15][16][17][58][59][60][61][62][63] . In this work, we perform molecular dynamics (MD) simulations to understand the properties of CH 4 + n-decane, CO 2 + n-decane, and CH 4 + CO 2 + n-decane systems over a broad range of temperature (313-442 K) and pressure (up to about 300 bar) relevant to geological processes.…”