Well-Defined Poly(ethylene oxide)−Polyacrylonitrile Diblock Copolymers as Templates for Mesoporous Silicas and Precursors for Mesoporous Carbons

Poly(ethylene oxide)−polyacrylonitrile (PEO-b-PAN) diblock copolymers were synthesized and used as supramolecular templates for mesoporous silicas and precursors for mesoporous carbons. The copolymers were prepared from poly(ethylene oxide) homopolymers through chain extension with polyacrylonitrile (PAN) via atom transfer radical polymerization and had a low polydispersity index (∼1.1), a degree of polymerization of PAN from 16 to 208, and a PAN content of 20−70 wt %. The copolymers were used as supramolecular templates for the formation of silica from tetraethyl orthosilicate in aqueous HCl solution. The obtained silica/PEO-b-PAN composites were calcined to obtain mesoporous silicas or heat-treated to convert PAN into carbon, the latter being isolated through the dissolution of silica. The silicas had specific surface areas of ∼550 m2 g-1, total pore volumes of 0.6−1.2 cm3 g-1, and uniform mesopores of diameter ∼10 nm, which appeared to be cylindrical with short-range ordering. The carbons had broad pore size distributions, yet some of them exhibited a certain degree of nanoscale ordering. Their surface areas were ∼900 m2 g-1, and the total pore volumes were 0.9−1.9 cm3 g-1. The carbons exhibited some degree of ordering of graphene sheets in their frameworks. A clear similarity between the silica pore shape and the carbon nanostructure shape was observed for samples from the silica/EO45AN43 composite.