Selective disordering of lamella-forming diblock copolymers under an electric field

Abstract

Self-assembled block polymers show great potential to serve as templates for the fabrication of nanoscale structures for devices, provided that structural features such as defects and global orientation can be fully and efficiently controlled. The most efficient way to control these features is by application of an electric field, to orient features parallel to the electric field. Several aspects of the thermodynamic and kinetic factors that determine the reorientation dynamics have been studied in recent years and are increasingly understood. Current experiments focus on reorientation close to the order-disorder transition (ODT) temperature, where an efficient mechanism involving selective disordering is long anticipated but subject to lively debate. Here, we complement the increasing experimental understanding by a detailed and unifying computational analysis of all distinct microscopic stages in this new reorientation mechanism. The unification step originates from the comparison of two different models, one based on a molecular description and the other phenomenological. The results have a general character and may also serve as a stepping stone for understanding microscopic response pathways due to other kinds of deformation, such as mechanical stress or shear. We find that reorientation is most effective for temperatures that are slightly below ODT, at which the system is slightly demixed and the balance between surface tension and the ponderomotive force is optimal. © 2011 The Royal Society of Chemistry

Kinetic pathways of sphere-to-cylinder transition in diblock copolymer melt under electric field

“…These mechanisms have also been confirmed in simulation works. [32][33][34] For cylinder-forming structures, results obtained by Xu et al 26 and Lyakhova et al 30 have shown that when an electric field was applied to a cylindrical structure aligned parallel to the electrode surface, the electric field causes cylindrical domains to break up into spheres, then these spheres reconnect and form cylinders oriented along the applied electric field. Under effect of an applied electric field the free energies of lamellae or cylindrical phases become minimal when the lamellae or the cylinders are aligned parallel to the applied field.…”

Modeling of Block Copolymer/Colloid Hybrid Composite Materials

“…Nonetheless, we believe that the phenomenology we are studying is rather general and, hence, we allow the freedom of choosing the parameters in Equation 4 as phenomenological constants. As we have shown recently [5,28] cell dynamics simulation (CDS) can be used in a tandem with a more elaborate technique like dynamics self-consistent field theory (DSCFT) which involves direct evaluation of the polymer path integrals. DSCFT is very computational expensive and using CDS as a research precursor can save time in problems involving parameter space search.…”

“…Previous studies have shown that this assumption can lead to experimental relevant results. [5,6] Since the polymer is treated in terms of its local monomer concentration we introduce a free energy functional which will provide…”

Electric Field Induced Selective Disordering in Lamellar Block Copolymers

“…Details as regards simulation method and parametrization of the dimensionless field strength are provided elsewhere. 7…”

“…9 Indeed, Braggpeaks measured in a scattering experiments are usually broadened in particular at their wings, where the intensity exhibits a smooth power .α denotes the applied field strength as a dimensionless parameter as discussed in Ref. 7 . E is directed vertically.…”