Hollow mesoporous organosilica nanospheres templated with flower-like micelles of pentablock copolymers

We present a facile preparation of hollow mesoporous organosilica nanospheres with well-defined, uniform mesopores by controlling the morphology of pentablock copolymer templates under acidic conditions. The CBABC type poly(lactic acid-co-glycolic acid)-b-poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(lactic acid-co-glycolic acid) (PLGA-b-PEO-b-PPO-b-PEO-b-PLGA) pentablock copolymers were synthesized via a step-growth and ring-opening polymerization method using Pluronic F68 and F108 as macro-initiators. Two kinds of pentablock copolymers, (LA(45)GA(12)) EO75PO30EO75(LA(45)GA(12)) and (LA(28)GA(9))EO141PO54 EO141(LA(28)GA(9)), were used as single soft templates to prepare mesoporous ethane-silica and benzene-silica hollow nanospheres by sol-gel chemistry in acidic aqueous solutions. The inner cavity diameter was controlled up to similar to 20 nm by varying acidity and the chain length of the hydrophobic PLGA block without using additional swelling agents. The evolution of hollow nanospheres could be explained by single flower-like micelle template mechanism and the variation of morphology of pentablock copolymers upon solution acidity. Moreover, the aminefunctionalized hollow benzene-silica nanospheres showed high carbon dioxide adsorption at ambient conditions. The hollow organosilica nanospheres were characterized by small-angle X-ray scattering, nitrogen adsorption-desorption, solid-state C-13- and Si-29 nuclear magnetic resonance, and scanning and transmission electron microscopy and so on. (C) 2018 Elsevier Inc. All rights reserved.