Janus Silica Hollow Spheres Prepared via Interfacial
Biosilicification
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Abstract
A poly(ethylene glycol)<i>-<i>b</i>-</i>poly(<sub>L</sub>-lysine)<i>-<i>b</i>-</i>poly(styrene)
(PEG-PLL-PS) triblock copolymer, which contains a cationic PLL block
as the middle block, is synthesized via a combination of ring-opening
polymerization (ROP) and atom-transfer radical polymerization (ATRP).
The PEG-PLL-PS (ELS) triblock is employed as a macromolecular surfactant
to form a stable oil-in-water (O/W) emulsion, which is subsequently
used as the template to prepare Janus silica hollow spheres (JHS)
via a one-pot biosilicification reaction. For the emulsion template,
the middle PLL block assembles at the O/W interface and directs the
biomimetic silica synthesis in the presence of phosphate buffer and
silicic acid precursors. This biosilicification process takes place
only in the intermediate layer between water and the organic interior
phase, leading to the formation of silica JHSs with hydrophobic PS
chains tethered to the inner surface and PEG attached to the outer
surface. The three-layer JHSs, namely, PEG/silica-polylysine/PS composites,
were verified by electron microscopy. Upon further breaking these
JHSs into species, polymer-grafted Janus silica nanoplates (JPLs)
can be obtained. Our studies provide an efficient one-step method
for preparing hybrid silica Janus structures within minutes