Pathway-Dependent Grain Coarsening of Block Copolymer Patterns under Controlled Solvent Evaporation

Block Copolymer-Templated, Single-Step Synthesis of Transition Metal Oxide Nanostructures for Sensing Applications

The synthesis of transition metal oxide nanostructures, thanks to their high surface-to-volume ratio and the resulting large fraction of surface atoms with high catalytic activity, is of prime importance for the development of new sensors and catalytic materials. Here, we report an economical, time-efficient, and easily scalable method of fabricating nanowires composed of vanadium, chromium, manganese, iron, and cobalt oxides by employing simultaneous block copolymer (BCP) self-assembly and selective sequestration of metal-organic acetylacetonate complexes within one of the BCP blocks. We discuss the mechanism and the primary factors that are responsible for the sequestration and conformal replication of the BCP template by the inorganic material that is obtained after the polymer template is removed. X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (PXRD) studies indicate that the metal oxidation state in the nanowires produced by plasma ashing the BCP template closely matches that of the precursor complex and that their structure is amorphous, thus requiring high-temperature annealing in order to sinter them into a crystalline form. Finally, we demonstrate how the developed nanowire array fabrication scheme can be used to rapidly pattern a multilayered iron oxide nanomesh, which we then used to construct a prototype volatile organic compound sensor.

Solvent-assisted self-assembly of block copolymer thin films

Solvent-assisted block copolymer self-assembly is a compelling method for processing and advancing practical applications of these materials due to the exceptional level of the control of BCP morphology and significant acceleration of ordering kinetics. Despite substantial experimental and theoretical efforts devoted to understanding of solvent-assisted BCP film ordering, the development of a universal BCP patterning protocol remains elusive; possibly due to a multitude of factors which dictate the self-assembly scenario. The aim of this review is to aggregate both seminal reports and the latest progress in solvent-assisted directed self-assembly and to provide the reader with theoretical background, including the outline of BCP ordering thermodynamics and kinetics phenomena. We also indicate significant BCP research areas and emerging high-tech applications where solvent-assisted processing might play a dominant role.