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All-in-One "Schizophrenic" Self-assembly of Orthogonally Tuned Thermoresponsive Diblock Copolymers

 
: Vishnevetskaya, Natalya S.; Hildebrand, Viet; Nizardo, Noverra M.; Ko, Chia-Hsin; Di, Zhenyu; Radulescu, Aurel; Barnsley, Lester C.; Müller-Buschbaum, Peter; Laschewsky, André; Papadakis, Christine M.

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Langmuir. The ACS journal of surfaces and colloids 35 (2019), No.19, pp.6441-6452
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
Deutsche Forschungsgemeinschaft DFG
Sachbeihilfe; MU 1487/17-1
Zweifach und orthogonal schaltbare Blockcopolymere aus zwitterionischen und thermoresponsiven Blöcken Synthese und Strukturen in Lösung und im dünnen Film
Deutsche Forschungsgemeinschaft DFG
Sachbeihilfe; PA 771/14-1
Zweifach und orthogonal schaltbare Blockcopolymere aus zwitterionischen und thermoresponsiven Blöcken Synthese und Strukturen in Lösung und im dünnen Film
English
Journal Article
Fraunhofer IAP ()
responsive polymer; self-assembly; block copolymer; UCST; LCST; Turbidimetry; small-angle neutron scattering (SANS)

Abstract
Smart, fully orthogonal switching was realized in a highly biocompatible diblock copolymer system with variable trigger-induced aqueous self-assembly. The polymers are composed of non-ionic and zwitterionic blocks featuring lower and upper critical solution temperatures (LCST, UCST). In the system investigated, diblock copolymers from poly(N-isopropyl methacrylamide) (PNIPMAM) and a poly(sulfobetaine methacrylamide), systematic variation of the molar mass of the latter block allowed for shifting the UCST of the latter above the LCST of the PNIPMAM block in salt free condition. Thus, successive thermal switching results in schizophrenic micellization, in which the roles of the hydrophobic core block and the hydrophilic shell block are interchanged in dependence on temperature. Furthermore , by virtue of the high electrolyte-sensitivity of the zwitterionic polysulfobetaine block, we succeeded to shift its UCST below the LCST of the PNIPMAM block by adding small amounts of an electrolyte, thus inverting the pathway of switching. This superimposed orthogonal switching by electrolyte addition enabled us to control the switching scenarios between the two types of micelles: (i) via a molecularly dissolved state, if the LCST-type cloud point is below the UCST-type cloud point, which is the case at low salt concentrations, or (ii) via an insoluble state, if the LCST-type cloud point is above the UCST-type cloud point, which is the case at high salt concentrations. Systematic variation of the block lengths allowed for verifying the anticipated behavior and identifying the molecular architecture needed. The versatile and tunable self-assembly offers manifold opportunities, e.g. for smart emulsifiers or for sophisticated carrier systems.

: http://publica.fraunhofer.de/documents/N-543726.html