posted on 2023-12-29, 19:08authored byStefan Engel, Pascal M. Jeschenko, Marcel van Dongen, Jonas C. Rose, Dominic Schäfer, Michael Bruns, Sonja Herres-Pawlis, Helmut Keul, Martin Möller
Soft polymer nanocapsules
and microgels, which can adapt
their
shape and, at the same time, sequester and release molecular payloads
in response to an external trigger, are a challenging complement to
vesicular structures like polymersomes. In this work, we report the
synthesis of such capsules by photo-cross-linking of coumarin-substituted
polyglycidyl ethers, which we prepared by Williamson etherification
of epichlorohydrin (ECH) repeating units with 7-hydroxycoumarin in
copolymers with tert-butyl glycidyl ether (tBGE). To control capsule size, we employed the prepolymers
in an o/w miniemulsion, where they formed a gel layer at the interface
upon irradiation at 365 nm by [2π + 2π] photodimerization
of the coumarin groups. Upon irradiation at 254 nm, the reaction could
be reversed and the gel wall could be repeatedly disintegrated and
rebuilt. We further demonstrated (i) reversible hydrophilization of
the gels by hydrolysis of the lactone rings in coumarin dimers as
a mechanism to manipulate the permeability of the capsules and (ii)
binding functional molecules as amides. Thus, the presented nanogels
are remarkably versatile and can be further used as a carrier system.