Ordered arrays of hollow carbon nanospheres and nanotubules from polyacrylonitrile grafted on ordered mesoporous silicas using atom transfer radical polymerization

摘要

Ordered arrays of hollow carbon nanospheres and nanotubules were synthesized using polyacrylonitrile (PAN) as a carbon precursor and ordered mesoporous silicas with spherical pores (large-pore FDU-12) and cylindrical pores (ultra-large-pore SBA-15) as templates. PAN was grafted on the surface of the silica template using surface-initiated atom transfer radical polymerization (ATRP). The pore size of the silica template was selected to be sufficiently large (20-30 nm) to ensure the stability of the carbon layer formed through the carbonization of PAN. In addition, the large mesopore size promoted the formation of hollow carbon structures even if the mesopores were nearly completely filled with the surface-grafted PAN. The carbon nanostructures isolated after the dissolution of the silica templates were found to be composed of hollow spherical or tubular structural units arranged in periodic arrays reflecting the structural symmetry of the template. The carbons exhibited high specific surface areas and bimodal mesopore size distributions related to the presence of pores within the structural units and between them. Our results suggest the applicability of the surface-initiated ATRP in the synthesis of ordered mesoporous carbons with hollow frameworks. They also provide a direct evidence of the uniformity of the polymer layers that can be grafted in nanopores using surface-initiated ATRP. (C) 2015 Elsevier Ltd. All rights reserved.