Synthesis of mesoporous silica from poly(ethylene oxide)/polystyrene copolymers: influence of block architecture and each copolymer block on porous size.

Several well defined block copolymers PEO-b-PS and PS-b-PEO-b-PS were synthesized by atom transfer radical polymerization using PEO-Br and Br-PEO-Br as macroinitiators. These copolymers were characterized by GPC and 1H NMR. Mesoporous silicas with large and tunable accessible pores were successfully synthesized by evaporation-induced self-assembly using block copolymers as templates. The structures of these materials were characterized by BET and TEM. When block copolymers possess similar hydrophobic block length but different block architecture, the pore size of mesoporous silica templated by triblock copolymers is larger than that templated by diblock copolymers. For diblock copolymers, with the increasing of PEO block, the mesoporous size decreases; and with the increasing of PS block, the mesoporous size increases. The increase in the degree of polymerization of the PS block leads to a loss of pore organization. When PS block reaches long enough, the product was not mesoporous silica but silica nanowire. In addition, a method of a preparation of block copolymers vesicles by EISA approach was accidentally found.