Control of carbon nanostructures via block copolymer self-assembly and their applications

Abstract

Nanoscale engineering of carbon materials is immensely demanded in various scientific areas. Block copolymer (BCP) self-assembly is an effective strategy for the facile and scalable fabrication of periodic nanostructures. Polyacrylonitrile (PAN)-containing BCPs can create carbon nanostructures by thermal carbonization of carbon precursor PAN block and pyrolysis of sacrificial block. However, due to the low chain mobility of PAN, precise control of BCP nanostructure is difficult. In this dissertation, carbon nanostructures with diverse dimensions are presented by introducing electric field directed self-assembly and vapor induced phase separation. First, highly ordered nitrogen doped carbon nanowire arrays were fabricated by BCP self-assembly under electric field. Large dielectric constant difference between distinct polymer blocks offers rapid alignment of block copolymer self-assembled nanodomains under electric field. The aligned carbon nanowires were applied to all-carbon NO$_2$ gas sensor realized by highly aligned structure and rich nitrogen composition. In addition, hierarchically porous carbon nanostructures were achieved by multiscale phase separations. Highly humid atmosphere promotes vapor induced phase separation phenomenon, generated submicrometer scale pores without templates. The synergistic effect of facile mass transport by interconnected macropores and large surface area by bicontinuous nanoscale pores make the hierarchically porous carbon nanostructures succesfully applied to metal-free oxygen reduction reaction catalyst. Taking advantage of well-established benefits from device oriented BCP nanostructure engineering, our approach proposes a viable route to diverse carbon nanostructures compatible to next generation device architectures.