Enhancement of the Photoalignment Stability of Block Copolymer Brushes by Anchor Segments

Abstract

It is known that the use of a homopolymer derived from a relatively high‐surface‐energy block moiety in a diblock copolymer as a substrate can facilitate phase separation of the block copolymer in the form of a layered structure parallel to the substrate. This is an effective approach for preparing a photoresponsive surface molecular brush for liquid‐crystal alignment. However, the alignment of the polymer brushes soon diminishes during elastic deformation of the polymeric substrate due to the weak interaction between the copolymer and polymeric substrate in the interfacial blend layer. In this study, rigid segments composed of N‐p‐anisylmaleimide were controllably introduced via copolymerization into a series of well‐defined diblock copolymers as “anchors” to resist the “drift” of the copolymer from a polymethyl methacrylate substrate at above its glass transition temperature. The anchoring mechanism and the stability of the aligned azobenzene polymeric brushes were systematically studied and compared.

Photocontrollable liquid-crystalline block copolymers: design, photo-directed self-assembly and applications

“…Specifically, various fascinating processes such as the simple photochemical process, the rich photoresponsive behaviour, and the miscible ability with other LC materials (Fig. 3c), [57][58][59] which have great influence on the MPS nanostructures of LCBCs. Undoubtedly, such photocontrollable features may bring about unique features along with them.…”

“…[43][44][45][46][47][48][49][50] As a kind of BCP with specific photoresponsive functions, the photoresponsive LCBC makes it possible to modulate nanopatterns by light, thereby realizing multi-scale, large-area, and high-throughput preparation of nanopatterns, [51][52][53][54][55][56] and applying them to the fabrication and processing of ICs. Furthermore, when one azobenzene (AZ)-containing polymer (azopolymer) is engineered as the mesogenic block of LCBCs, various fascinating processes such as photoalignment, phototriggered molecular cooperative motion, photoinduced phase transition, and even absorbing and transforming light energy can be acquired, [57][58][59][60] which has great influence on the MPS nanostructures of LCBCs. In addition, similar to the photoresist as a photoresponsive material, [61][62][63] the photocontrollable LCBC is responsive to actinic light and can be used as a novel type of photoresist for photolithography processing.…”

Regulating Surface Topography of Liquid‐Crystalline Polymers by External Stimuli

“…Incorporating a photoresponsive LCP as one segment of block copolymer, photocontrol can be applied to manipulate the MPS nanostructure of polymer film. [71][72][73] When the mesogenic block serves as the continuous phase in LC block copolymer (LCBC), the orientation of MPS nanostructure can be controlled by tuning the polarization direction of the actinic light. [74] For example, linearly polarized light (LPL) at 488 nm is an effective method to control the orientation of poly(ethylene oxide) (PEO) nanocylinders in an amphiphilic LCBC with PEO as the hydrophilic block and one azobenzenecontaining LCP as the hydrophobic block.…”