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Open AccessArticle

Exploring Poly(ethylene glycol)-Polyzwitterion Diblock Copolymers as Biocompatible Smart Macrosurfactants Featuring UCST-Phase Behavior in Normal Saline Solution

1
University of Potsdam, Institute of Chemistry, Karl-Liebknecht-Str. 24–25, D-14476 Potsdam-Golm, Germany
2
Fraunhofer Institute of Applied Polymer Research IAP, Geiselberg-Str. 69, D-14476 Potsdam-Golm, Germany
*
Author to whom correspondence should be addressed.
Permanent address: University of Indonesia, Department of Chemistry, Kampus UI Depok, Depok 16424, West Java, Indonesia.
Polymers 2018, 10(3), 325; https://doi.org/10.3390/polym10030325
Received: 31 January 2018 / Revised: 12 March 2018 / Accepted: 13 March 2018 / Published: 15 March 2018
(This article belongs to the Special Issue Stimuli Responsive Polymers)
Nonionic-zwitterionic diblock copolymers are designed to feature a coil-to-globule collapse transition with an upper critical solution temperature (UCST) in aqueous media, including physiological saline solution. The block copolymers that combine presumably highly biocompatible blocks are synthesized by chain extension of a poly(ethylene glycol) (PEG) macroinitiator via atom transfer radical polymerization (ATRP) of sulfobetaine and sulfabetaine methacrylates. Their thermoresponsive behavior is studied by variable temperature turbidimetry and 1H NMR spectroscopy. While the polymers with polysulfobetaine blocks exhibit phase transitions in the physiologically interesting window of 30–50 °C only in pure aqueous solution, the polymers bearing polysulfabetaine blocks enabled phase transitions only in physiological saline solution. By copolymerizing a pair of structurally closely related sulfo- and sulfabetaine monomers, thermoresponsive behavior can be implemented in aqueous solutions of both low and high salinity. Surprisingly, the presence of the PEG blocks can affect the UCST-transitions of the polyzwitterions notably. In specific cases, this results in “schizophrenic” thermoresponsive behavior displaying simultaneously an UCST and an LCST (lower critical solution temperature) transition. Exploratory experiments on the UCST-transition triggered the encapsulation and release of various solvatochromic fluorescent dyes as model “cargos” failed, apparently due to the poor affinity even of charged organic compounds to the collapsed state of the polyzwitterions. View Full-Text
Keywords: block copolymer; amphiphile; macrosurfactant; thermoresponsive self-assembly; polyzwitterion; upper critical solution temperature (UCST); salting-in block copolymer; amphiphile; macrosurfactant; thermoresponsive self-assembly; polyzwitterion; upper critical solution temperature (UCST); salting-in
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MDPI and ACS Style

Nizardo, N.M.; Schanzenbach, D.; Schönemann, E.; Laschewsky, A. Exploring Poly(ethylene glycol)-Polyzwitterion Diblock Copolymers as Biocompatible Smart Macrosurfactants Featuring UCST-Phase Behavior in Normal Saline Solution. Polymers 2018, 10, 325.

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