Climate change requires enhanced autonomous temperature
monitoring
during logistics/transport. A cheap approach comprises the use of
temperature-sensitive copolymers that undergo temperature-induced
irreversible coagulation. The synthesis/characterization of pentablock
copolymers (PBCP) starting from poloxamer PEO130-b-PPO44-b-PEO130 (poly(ethylene
oxide)130-b-poly(propylene oxide)44-b-poly(ethylene oxide)130) and
adding two terminal qPDMAEMA85 (quaternized
poly[(2-dimethylamino)ethyl methacrylate]85) blocks is
presented. Mixing of PBCP solutions with hexacyanoferrate(III)/ferricyanide
solutions leads to a reduction of the decane/water interfacial tension
accompanied by a co/self-assembly toward flower-like micelles in cold
water because of the formation of an insoluble/hydrophobic qPDMAEMA/ferricyanide complex. In cold water, the PEO/PPO
blocks provide colloidal stability over months. In hot water, the
temperature-responsive PPO block is dehydrated, leading to a pronounced
temperature dependence of the oil–water interfacial tension.
In solution, the sticky PPO segments exposed at the micellar corona
cause a colloidal clustering above a certain threshold temperature,
which follows Smoluchowski-type kinetics. This coagulation remains
for months even after cooling, indicating the presence of a kinetically
trapped nonequilibrium state for at least one of the observed micellar
structures. Therefore, the system memorizes a previous suffering of
heat. This phenomenon is linked to an exchange of qPDMAEMA-blocks bridging the micellar cores after PPO-induced clustering.
The addition of ferrous ions hampers the exchange, leading to the
reversible coagulation of Prussian blue loaded micelles. Hence, the
Fe2+ addition causes a shift from history monitoring to
the sensing of the present temperature. Presumably, the system can
be adapted for different temperatures in order to monitor transport
and storage in a simple way. Hence, these polymeric “flowers”
could contribute to preventing waste and sustaining the quality of
goods (e.g., food) by temperature-induced bouquet formation, where
an irreversible exchange of “tentacles” between the
flowers stabilizes the bouquet at other temperatures as well.