Characterisation of hydration and nanophase separation during the temperature response in hydrophobic/hydrophilic elastin-like polypeptide (ELP) diblock copolymers.
To understand the complex nanoscale dehydration process during the lower critical solution temperature (LCST) based inverse phase transition of a class of thermoresponsive biopolymers, diblock elastin-like polypeptides (ELPs) were investigated by spin probing continuous wave electron paramagnetic resonance (CW EPR) spectroscopy. The diblock copolymers composed of a hydrophobic block and a hydrophilic block showed different mechanisms of a temperature-driven phase transition. While the phase transition temperature is a function of the hydrophobic mass fraction of the diblock ELPs, the hydrophilic block length determines the molecular structure of the polymer aggregates formed above the transition temperature. When the weight ratio of hydrophilic block length to hydrophobic block length is greater than or equal to 0.3, the polymer aggregates consist of a hydrophobic core and a hydrophilic corona. The interface of these two regions become permeable at temperatures above the transition temperature. In case of smaller ratios, the aggregating hydrophobic parts of the polymer enclose the hydrated hydrophilic blocks, that are too small to form a hydrophilic corona, leading to bigger and less dense aggregates of higher polarity.
Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany. dariush.hinderberger@chemie.uni-halle.de.
Katharina
K
Widder
Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Campus Box 90281, Durham, North Carolina 27708, USA.
Sarah R
SR
MacEwan
Laboratoire de Chimie des Polymères Organiques, CNRS UMR 5629, Université de Bordeaux, Bordeaux-INP, Pessac 33607 Cedex, France.
Elisabeth
E
Garanger
Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany. dariush.hinderberger@chemie.uni-halle.de.
Vanesa
V
Núñez
Laboratoire de Chimie des Polymères Organiques, CNRS UMR 5629, Université de Bordeaux, Bordeaux-INP, Pessac 33607 Cedex, France.
Sébastien
S
Lecommandoux
Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Campus Box 90281, Durham, North Carolina 27708, USA.
Ashutosh
A
Chilkoti
Institut für Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany. dariush.hinderberger@chemie.uni-halle.de.
Dariush
http://orcid.org/0000-0002-6066-7099
D
Hinderberger