Volume 128, 2005

Responsive brushes and gels as components of soft nanotechnology

Abstract

Progress in the development of generic molecular devices based on responsive polymers is discussed. Characterisation of specially synthesised polyelectrolyte gels, “grafted from” brushes and triblock copolymers is reported. A Landolt pH-oscillator, based on bromate/sulfite/ferrocyanide, with a room temperature period of 20 min and a range of 3.1 < pH < 7.0, has been used to drive periodic oscillations in volume in a pH responsive hydrogel. The gel is coupled to the reaction and changes volume by a factor of at least 6. A continuously stirred, constant volume, tank reactor was set-up on an optical microscope and the reaction pH and gel size monitored. The cyclic force generation of this system has been measured directly in a modified JKR experiment. The responsive nature of polyelectrolyte brushes, grown by surface initiated ATRP, have been characterised by scanning force microscopy, neutron reflectometry and single molecule force measurements. Triblock copolymers, based on hydrophobic end-blocks and either polyacid or polybase mid-block, have been used to produce polymer gels where the deformation of the molecules can be followed directly by SAXS and a correlation between molecular shape change and macroscopic deformation has been established. The three systems studied allow both the macroscopic and a molecular response to be investigated independently for the crosslinked gels and the brushes. The triblock copolymers demonstrate that the individual response of the polyelectrolyte molecules scale-up to give the macroscopic response of the system in an oscillating chemical reaction.

Article information

Article type
Paper
Submitted
15 Apr 2004
Accepted
10 May 2004
First published
14 Sep 2004

Faraday Discuss., 2005,128, 55-74

Responsive brushes and gels as components of soft nanotechnology

A. J. Ryan, C. J. Crook, J. R. Howse, P. Topham, R. A. L. Jones, M. Geoghegan, A. J. Parnell, L. Ruiz-Pérez, S. J. Martin, A. Cadby, A. Menelle, J. R. P. Webster, A. J. Gleeson and W. Bras, Faraday Discuss., 2005, 128, 55 DOI: 10.1039/B405700G

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