Liquid‐Crystalline Polymer and Block Copolymer Domain Alignment Controlled by Free‐Surface Segregation

Abstract

An orientational change from homeotropic to planar of liquid crystal (LC) mesogens and the microphase separation (MPS) domains is attained by the segregated skin layer at the free surface. This allows for an efficient in-plane photoalignment of the cylindrical domains. The surface segregation strategy is very simple and is therefore expected to open up new possibilities for the orientation control of various types of LC materials.

Alternation of Side-Chain Mesogen Orientation Caused by the Backbone Structure in Liquid-Crystalline Polymer Thin Films

“…Orientations of rodlike 9 and discotic 18 mesogens and further microphase separation structures of block copolymer films have been controlled by the existence of a segregated surface 14 and a topcoat layer. 15,19 An unusual endon (vertical) orientation of a conducting polymer chains has also been performed via surface segregation of one end of the polymer.…”

“…9,14,15 To clarify the role of the free surface, the free surfaces of the films were microscopically covered by inkjet printing. Inversely, a Langmuir XXXX, XXX, XXX−XXX PCBMA line was printed in the same manner onto a PCBA film.…”

Exploitation of Self‐Assembly Phenomena in Liquid‐Crystalline Polymer Phases for Obtaining Multifunctional Materials

“…the air-film interface) of thin films. In particular, it was possible to adjust the free surface by exploiting the surface segregation of a small amount of a free-surface-active polymer: this promoted a homeotropic-to-parallel orientation change of LC mesogens, which further led to an efficient in-plane photoalignment of microphase separation domains of a relevant liquid-crystalline block copolymer induced by LPL [51]. To this aim, the authors investigated the alignment behavior of a LC azobenzene homopolymer spin-cast film from a chloroform solution.…”

Free Surface-Induced Planar Orientation in Liquid Crystalline Block Copolymer Films: On the Design of Additive Surface Active Polymer Layer

“…In such system, it was expected that the addition of a minor amount of PBMA-b-P5Az10MA in the PS-b-P5Az10MA film crucially changes the molecular and domain orientations from a homeotropic direction to a planar one. Upon annealing, the blended PBMA-b-P5Az10MA segregates to the free (air) surface in the blend film due to the lower surface tension, and acts as a surface active polymer (SAP) [12]. The planaly oriented MPS cylinder domains are then readily aligned homogeneously by irradiation with linearly polarized light (LPL) (Scheme 1) [12].…”

“…Upon annealing, the blended PBMA-b-P5Az10MA segregates to the free (air) surface in the blend film due to the lower surface tension, and acts as a surface active polymer (SAP) [12]. The planaly oriented MPS cylinder domains are then readily aligned homogeneously by irradiation with linearly polarized light (LPL) (Scheme 1) [12]. Surface segregation at the surface and interface is of practical importance [13][14][15].…”