The Core-Shell Approach to Formation of Ordered Nanoporous Silicas by MPEG-b-PLA Block Copolymers

Selected MPEG-b-PLA block copolymer templates have been synthesized by ring-opening polymerization, with systematic variation of the chain lengths of the hydrophilic and hydrophobic blocks. The size and shape of the micelles that spontaneously form in solution are controlled by the characteristics of the block copolymer template. Tunable pore sizes ranging from 2 to 8 nm were achieved in the templated synthesis of ordered nanoporous silica by increasing the hydrophobic chain lengths. The highest surface area observed by BET analysis was 660 m2/g. The formation mechanism of these nanoporous structures, obtained by controlling the micelle size, has been confirmed using both liquid and solid state 13C and 29Si NMR techniques. This work verifies the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of the hydrophobic cores and hydrophilic shells of the block copolymer templates.