Electric Field Induced Sphere-to-Cylinder Transition in Diblock Copolymer Thin Films

Abstract

An electric field induced sphere-to-cylinder transition in thin films of asymmetric polystyrene-b-poly(methyl methacrylate) diblock copolymers was observed. In the absence of an applied electric field, thin films of the asymmetric diblock copolymer consisted of layers of spherical microdomains with poor in-plane long-range ordering. Under a ∼40V/μm applied electric field, hexagonally packed cylindrical microdomains normal to the surface were found. Cross-sectional transmission electron microscopy images of the intermediate stages of the alignment indicated that, under an electric field, the asymmetric diblock copolymer formed spherical microdomains that were deformed into ellipsoids and, with time, interconnected into cylindrical microdomains oriented in the direction of the applied electric field. Simulations suggest that improved long-range order of the cylindrical microdomains could be achieved by cycling the electrical field.

Electric field manipulated nanopatterns in thin films of metalorganic 3-miktoarm star terpolymers

“…34 Xu et al demonstrated that the improvement of the long-range order in a bcc phase of a non-metal-containing block copolymer upon application of electric fields can only be accomplished by first inducing an order-order phase transition from spheres into a cylindrical microdomain structure which is aligned by the electric field, and by subsequent reformation of the bcc structure. 35 This stands in clear contrast to the results of our experiments which show that improved ordering can be achieved in bcc forming thin films of PS-b-PFEMS without requiring a prior phase transition into an uniaxial phase. We therefore conclude that the improved order may be related to polarization of the iron-containing PFEMS spheres, which is specific for block copolymers with a metalcontaining minority block.…”

“…It is known that in bcc or gyroid morphologies, frustration occurs independent of the orientation of the microdomains with respect to E. 34,35 In these cases, electric fields induce phase transitions into uniaxial structures when the composition of the block copolymer is near a phase boundary. 34 Xu et al demonstrated that the improvement of the long-range order in a bcc phase of a non-metal-containing block copolymer upon application of electric fields can only be accomplished by first inducing an order-order phase transition from spheres into a cylindrical microdomain structure which is aligned by the electric field, and by subsequent reformation of the bcc structure.…”

Influence of Electric Field on the Phase Transitions of the Hexagonal Cylinder Phase of Diblock Copolymers

“…The same process has been observed experimentally from cross-sectional TEM images of copolymer thin films of a polystyrene-b-poly(methyl methacrylate) diblock under the influence of electric fields. [10] On continued exposure to the electric field, increasingly more ellipsoids and cylinders connect with their neighbors and finally, long-range-ordered structures are formed. We observe that the cylindrical structures tended to connect at nonzero angles with respect to the electric field lines, but the long-range-ordered structures form mainly along the direction of the external electric field.…”

“…Recently, the experimental finding that electric fields induce sphere-to-cylinder transitions in diblock copolymer thin films was reported. [10] In the absence of an applied electric field, thin films of the asymmetric diblock copolymer consist of layers of spherical microdomains possessing poor in-plane long-range ordering. Under an applied electric field of 40 V m…”

“…[10] Cell dynamics simulation (CDS), a cellular automation method, was developed to model interface dynamics in phase separating systems. [11][12][13][14] CDS methods have been used extensively to simulate spinodal decomposition in binary blends [4,[11][12][13] and the corresponding effects of shearing.…”