Autonomous Volume Transitions of a Polybase Triblock Copolymer Gel in a Chemically Driven pH-Oscillator |
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| Authors: | Paul D Topham Jonathan R Howse Colin J Crook Anthony J Gleeson Wim Bras Steven P Armes Richard A L Jones Anthony J Ryan |
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| Institution: | 1. Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK;2. Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK;3. CCLRC Daresbury Laboratory, Warrington, WA4 4AD, UK;4. DUBBLE CRG, ESRF, 6 rue Jules Horowitz, BP 220, F-38043 Grenoble Cédex 9, France |
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| Abstract: | Summary: A pH-responsive ABA triblock copolymer, comprising poly(methyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate)-block-poly(methyl methacrylate) PMMA-b-PDEA-b-PMMA], has been cast into thin films with a well-defined microstructure. Small Angle X-ray Scattering (SAXS) and Atomic Force Microscopy (AFM) studies confirm that this copolymer forms a hydrogel consisting of PMMA spheres embedded within a polybase PDEA matrix, with the PMMA domains acting as physical cross-links. The hydrogel has a pH-reversible coil-globule transition at around pH 4.5. This responsive physical property was exploited by immersing a sample of copolymer hydrogel in an aqueous solution containing a cyclic pH-oscillating reaction, whereby the pH was continuously oscillated above and below the transition pH so as to induce autonomous volume transitions. The changes in microscopic and macroscopic length scales correlate closely during (de)swelling cycles, with affine behaviour occurring over five orders of magnitude. |
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| Keywords: | pH-responsive Polybase poly(2-(diethylamino)ethyl methacrylate) SAXS triblock copolymer |
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