Electrochemical Applications of Microphase‐Separated Block Copolymer Thin Films

Abstract

In this review, we discuss electrochemical applications of electrode-supported thin films derived from microphase-separated block copolymers (BCPs). In contrast to conventional homopolymers used for electrode modification, BCPs afford periodic nanoscale structures (microdomains) of uniform dimensions (5-100 nm) and predictable morphologies, which can be controlled by adjusting the lengths of individual homopolymer segments. BCPs usable for electrochemical applications consist of two or more segments that form solute-permeable, redox-active or etchable microdomains and a chemically inert matrix. The resulting microdomains afford nanoscale molecular/charge transport pathways toward the underlying electrode, whereas the matrix serves as a scaffold to improve film stability in solution. These polymeric thin films provide a unique means for fabricating nanowire arrays via template-based electrochemical synthesis, designing electrochemical sensors with unique selectivity, and constructing electrochemically-tunable functional materials.[a] Prof.

Nanoscale Block Copolymer Self‐Assembly and Microscale Polymer Film Dewetting: Progress in Understanding the Role of Interfacial Energies in the Formation of Hierarchical Nanostructures

“…The self‐assembly (SA) of block copolymers (BCPs) into ordered nanostructures on solid surfaces is a promising candidate for next‐generation lithography which is reaching real world applications, for instance, in the creation of fin‐field effect transistors, surface enhanced Raman spectroscopy‐active surfaces, magnetic storage media, or electrochemical sensors . BCP lithography is based on the so‐called microphase separation of block copolymers containing two (or more) blocks of incompatible polymer species: Depending on block length ratio, Flory–Huggins parameter, and polymerization degree, the BCPs separate into arrays of the different blocks, leading to versatile structures with nanoscale feature size and periodicity.…”

Block Copolymer‐Derived Recessed Nanodisk‐Array Electrodes as Platforms for Folding‐Based Electrochemical DNA Sensors

“…Recessed nanodisk‐array electrodes (RNEs), electrodes coated with insulating layers comprising vertically‐oriented cylindrical nanopores with uniform diameters, were explored to design unique electrochemical sensors . The nanoporous layers of RNEs were based on anodic alumina or track‐etched membranes, or were fabricated from cylinder‐forming block copolymer thin films upon the selective removal of the cylindrical microdomains . RNEs were shown to give high sensitivity in faradaic current measurements due to the overlapping of analyte diffusion layers developed from individual pores and also a small charging current that reflected the small active electrode area .…”

“…In this study, the electrochemical characteristics of RNE‐based E‐DNA sensors (Scheme ) were investigated, and compared with those of their film‐free counterparts. RNEs were fabricated by coating planar gold substrates with nanoporous thin films derived from cylinder‐forming diblock copolymers, polystyrene‐ block ‐poly(methylmethacrylate) (PS‐ b ‐PMMA) . The nanoporous films were obtained by the selective removal of cylindrical PMMA microdomains orienting perpendicular to the underlying gold electrodes .…”

“…The gold surface of such a RNE was modified with a thiolated stem‐loop DNA probe (SLP) with a methylene blue (MB) tag . PS‐ b ‐PMMA‐derived nanoporous thin films are suitable to investigate the effects of nanoconfinement on the characteristics of E‐DNA sensors for the following reasons . First, the uniform and controllable (10–50 nm) pore diameter permits the systematic investigation of the influences of nanopore diameter on sensor performance.…”

“…[23,24] The nanoporous layers of RNEs were based on anodic alumina or track-etched membranes, [25][26][27] or were fabricated from cylinder-forming block copolymer thin films upon the selective removal of the cylindrical microdomains. [28,29] RNEs were shown to give high sensitivity in faradaic current measurements due to the overlapping of analyte diffusion layers developed from individual pores and also a small charging current that reflected the small active electrode area. [30] The nanoporous layers of RNEs exhibited size-based [31,32] and charge-based [33,34] permeability for redox-active biomolecules and small ions, respectively.…”