Solvent selectivity governs the emergence of temperature responsiveness in block copolymer self-assembly

Alessandro Ianiro (Corresponding author), Marco M.R.M. Hendrix, Paul Joshua Hurst, Joseph P. Patterson, Mark Vis, Michael Sztucki, A. Catarina C. Esteves, Remco Tuinier

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

In highly selective solvents, block copolymers (BCPs) form association colloids, while in solvents with poor selectivity, they exhibit a temperature-controlled (de)mixing behavior. Herein, it is shown that a temperature-responsive self-assembly behavior emerges in solvent mixtures of intermediate selectivity. A biocompatible poly-ethylene(oxide)-block-poly-ϵ-caprolactone (PEO-PCL) BCP is used as a model system. The polymer is dissolved in solvent mixtures containing water (a strongly selective solvent for PEO) and ethanol (a poorly selective solvent for PEO) to tune the solvency conditions. Using synchrotron X-ray scattering, cryogenic transmission electron microscopy, and scanning probe microscopy, it is shown that a rich temperature-responsive behavior can be achieved in certain solvent mixtures. Crystallization of the PCL block enriches the phase behavior of the BCP by promoting sphere-to-cylinder morphology transitions at low temperatures. Increasing the water fraction in the solvent causes a suppression of the sphere-to-cylinder morphology transition. These results open up the possibility to induce temperature-responsive properties on demand in a wide range of BCP systems.

Original languageEnglish
Pages (from-to)2912-2920
Number of pages9
JournalMacromolecules
Volume54
Issue number6
DOIs
Publication statusPublished - 4 Mar 2021

Bibliographical note

Funding Information:
The authors thank the European Synchrotron Radiation Facility (Grenoble, France) for the provision of synchrotron radiation facilities and the ID02 beamline staff for the excellent support. Furthermore, the authors thank Lisa Timmers for help with the SAXS measurements. Cryo-TEM images were obtained using the instrumentation at the IMRI (ps.uci.edu/imri/) facilities at UC Irvine. M.V. acknowledges the Netherlands Organisation for Scientfic Research (NWO) for a Veni grant (no. 722.017.005). The authors thank M. Chi for kindly performing the DSC characterization of PEO and PCL homopolymers.

Publisher Copyright:
© XXXX 2021 The Authors. Published by American Chemical Society.

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

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