SCFT Study of Diblock Copolymer Melts in Electric Fields: Selective Stabilization of Orthorhombic Fddd Network Phase

Abstract

Using self-consistent field theory (SCFT), we explore the phase behavior of a diblock copolymer (BCP) melt in an applied electric field, with different dielectric constants assigned to each monomer type. The electric field penalizes the interfaces between species domains that are not parallel to the field. Under the present mean-field approximation, lamellar and cylindrical structures reorient to align their interfaces with the electric field, such that these mesophases will have the same electrostatic free energy contribution as the mixed (disordered) state, and their relative stability will remain unchanged. In contrast, sphere and network phases do not have an axis of dielectric uniformity; consequently, the preferred orientation and morphological response of these phases must be determined numerically. We compute the phase diagram for a BCP melt in the presence of an applied electric field by comparing the free energy of each phase at its thermodynamically preferred orientation relative to the electric field vector. We find that the stability regions of the sphere and network phases shrink with increasing field strength, in favor of the disordered, cylindrical, and lamellar phases. Moreover, the double gyroid network phase is more strongly disfavored than the orthorhombic Fddd network phase, such that the predicted region of stability for the Fddd phase is shifted to larger segregation strength (lower temperature).

Nonequilibrium Processes in Polymer Membrane Formation: Theory and Experiment

“…Given the abiding interest that membrane fabrication has attracted since the seminal works of Bechhold, Kolff and Berk, and Loeb and Sourirajan, we cannot aim for a comprehensive overview but have selected topics related to membrane structure and its nonequilibrium formation processes to highlight common aspects of experiment and theory. Therefore, various important and challenging topics of interest such as, e.g., solvent evaporation from homopolymer mixtures, − solvent annealing of copolymer films, − directing the orientation of membrane pores by electric fields, − polymerization-induced phase-separation (PIPS), or polymerization-induced self-assembly (PISA) − have not been covered. Functionalization of membrane pores , and molecular transport on the atomic scale in the membranes that are critical for the operation of membranes are also not addressed in the following.…”

Vertical Cylinder-to-Lamella Transition in Thin Block Copolymer Films Induced by In-Plane Electric Field

“…The possibility of using a DC electric field for the orientation of block copolymer lamellae along the field lines was first demonstrated by Amundson et al in the early 90s [33][34][35]. Since then, the electric field effects have been investigated rather intensively Polymers 2021, 13, 3959 2 of 15 experimentally [36][37][38][39][40][41][42][43][44][45][46][47][48], by analytical/numerical theory [49][50][51][52][53][54][55][56][57][58][59][60], and via computer simulations [61][62][63]. It was demonstrated that the electric field has a strong impact on the conditions of order-disorder and order-order transitions in block copolymer melts, solutions, and thin films and can be considered as a precision tool to adjust the morphology of microphase-separated states on a nanometer scale.…”

Thickness-Dependent Photo-Aligned Thin-Film Morphologies of a Block Copolymer Containing an Azobenzene-Based Liquid Crystalline Polymer and a Poly(ionic liquid)

“…BCPs composed of two or more incompatible segments can obtain excellent properties of each segment orthogonally by self-assembling to form various ordered nanostructures, including spheres, hexagonally packed cylinders (HEX), lamellae (LAM), the gyroid network phase (GYR), and the Fddd network phase (O 70 ). − However, many properties of BCPs, including the modulus and conductivity, are usually affected by the long-range order of nanostructures. − Fortunately, thin-film assembly of BCPs provides a fascinating approach for preparing thin films with long-range ordered nanostructures. In the past decades, various strategies, including magnetic field, electric field, − graphoepitaxy, − solvent vapor annealing, ,, and supramolecular cooperative motions (SMCMs), ,− have been explored to control the orientation of nanostructures in BCP thin films.…”