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Switch it Inside-out. "Schizophrenic Behavior of All Thermoresponsive UCST-LCST Diblock Copolymers

: Papadakis, Christine M.; Müller-Buschbaum, Peter; Laschewsky, André


Langmuir. The ACS journal of surfaces and colloids 35 (2019), No.30, pp.9660-9676
ISSN: 0743-7463
ISSN: 1520-5827
Deutsche Forschungsgemeinschaft DFG
Sachbeihilfe; LA 611/11-1
Zweifach und orthogonal schaltbare Blockcopolymere aus zwitterionischen und thermoresponsiven Blöcken Synthese und Strukturen in Lösung und im dünnen Film
Journal Article
Fraunhofer IAP ()
progammable materials; responsive polymer; synthesis; phase behavior; thin film; scattering methods

This feature article reviews our recent advancements on the synthesis, the phase behavior and the micellar structures of diblock copolymers consisting of oppositely thermoresponsive blocks in aqueous environments. These copolymers combine a non-ionic block, which shows lower critical solution temperature (LCST) behavior, with a zwitterionic block that exhibits an upper critical solution temperature (UCST). The transition temperature of the latter class of polymers is strongly controlled by its molar mass and by the salt concentration, in contrast to the rather invariant transition of non-ionic polymers with type II LCST behavior, such as poly(N-isopropyl acrylamide) or poly(N-isopropyl methacrylamide). This allows for implementing the sequence of the UCST and LCST transitions of the polymers at will, by adjusting either molecular or, alternatively, physical parameters. Depending on the location of the transition temperatures of both blocks, different switching scenarios are realized from micelles to inverse micelles, namely via the molecularly dissolved state, the aggregated state or directly. In addition to studies of (semi)dilute aqueous solutions, also highly concentrated systems have been explored, namely water-swollen thin films. Concerning applications, we discuss the possible use of the diblock copolymers as nanocarriers.