Hollow mesoporous silica nanospheres using pentablock copolymer micelle templates

We developed hollow mesoporous silica nanospheres by a sol-gel process utilizing pentablock copolymer templates 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) under acidic aqueous conditions. Four kinds of water-soluble pentablock copolymers were used as structure-tuning agents and tetraethyl orthosilicate (TEOS) was used as a silica precursor. Hollow mesoporous silica nanoparticles were prepared at room temperature without any additive salts, which is the main key issue compared with the other reports. The hollow structure was found when pentablock copolymer with longer chain length was used, while a bimodal pore structure was obtained using shorter copolymer templates. Moreover, hydrothermal stability for the hollow mesoporous silica samples was investigated inside distilled water at 100 °C for 28 d. It is noteworthy that pore structure and morphology were varied depending on the length scale of pentablock copolymer templates and the hollow mesopore structure was obtained from single- and partially bridged micelle templates at room temperature.