We have produced hybrid poly(urethane–urea)/silica
nanocapsules
with controlled molecular-scale regimes of silica that break upon
introduction into basic media. The miniemulsion technique used is
simple and scalable but yields complex molecular-scale morphologies
that create molecular gates for the release of hydrophilic components.
The hybrid nanocapsules displayed no microphase separation, indicating
the formation of microscopically mixed regions of silica and poly(urethane–urea).
Using atomic force microscopic techniques, we characterize the mechanical
properties of individual capsules and identify the tailorability of
the capsule modulus by changing the ratio of isocyanate to silica
in the precursor mixture. The compositions of the hybrids were confirmed
by infrared spectroscopy and thermogravimetric analysis. The change
in size of a nanocapsule with pH and time was monitored by fluorescence
correlation spectroscopy to evaluate their potential as nanocontainers
and show a pH-responsive release
