A scalable synthetic muscle has been constructed that transducts nanoscale molecular shape changes into macroscopic motion. The working material, which deforms affinely in response to a pH stimulus, is a self-assembled block copolymer comprising nanoscopic hydrophobic domains in a weak polyacid matrix. A device has been assembled where the muscle does work on a cantilever and the force generated has been measured. When coupled to a chemical oscillator this provides a free running chemical motor that generates a peak power of 20 mW kg(-1) by the serial addition of 10 nm shape changes that scales over 5 orders of magnitude. It is the nanostructured nature of the gel that gives rise to the affine deformation and results in a robust working material for the construction of scalable muscle devices.

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.

The phase behavior of gels of E40B10 in 0.2 mol dm-3 aqueous K2SO4 was studied as a function of temperature and concentration. E40B10 is a diblock copolymer of poly(oxyethylene) (E) and poly(oxybutylene) (B), where the subscripts denote the number of repeats. The phase of the material was characterized by both simultaneous rheology and small-angle X-ray scattering, (SAXS). Depending on polymer volume fraction in the range 23−38% a body-centered cubic (bcc) structure or a face-centered cubic (fcc) structure was observed at low temperature, and at high temperature a hexagonally packed rod structure was formed. The phase transitions were shown to be characterized by discontinuous changes in the values of the dynamic shear moduli. A bcc−fcc transition was observed at high concentration, the corresponding transition temperature increasing with increasing polymer concentration. The effects of reciprocating shear were shown to increase the degree of order, manifested as a sharpening of the diffraction peaks in the SAXS pattern. The dynamic moduli decreased rapidly on the application of oscillatory shear and recovered equally rapidly when the deformation ceased. The decrease in moduli was shown, via the SAXS patterns acquired simultaneously, to be correlated to structural changes within the gel.

Micellar ordering in semidilute solutions of polystyrene−polyisoprene diblock and triblock copolymers in the slightly selective solvent di-n-butyl phthalate has been studied using rheology and small-angle X-ray scattering (SAXS). Ordering as a function of temperature has been investigated for a range of polymer concentrations 0.1 ≤ φ ≤ 0.4. For φ < 0.2, the rheological response is liquidlike and SAXS shows that there is no intermicellar order in the liquid; however, the solution viscosity shows a strong maximum near 50 °C. Above a crossover concentration φ ≈ 0.2, ordering of micelles is indicated by the presence of a sharp structure factor peak. The ordered micellar structure, identified as hexagonal for 0.2 ≤ φ ≤ 0.3 and lamellar for φ ≥ 0.3, persists up to an order−disorder transition at T ≈ 40 °C for the diblock and T ≈ 50 °C for the triblock solutions studied. The rheological characteristics of the ordered solutions are reminiscent of those found in ordered block copolymer melts. At higher temperatures, for example approximately 20−30 °C above the ODT for the φ = 0.2 solutions, indications of chain aggregation disappear from the rheological properties; however, some evidence of chain association persists to still higher temperatures in the SAXS profiles. The domain spacing, d, in the ordered solutions obtained from the principal structure factor peak position, shows a crossover at φ ≈ 0.2, in agreement with rheology. At high concentrations, d scales as d ∼ φ-1/3, suggesting a three-dimensional contraction of the microstructure, and thus micelles of finite length. This concentration dependence is opposite to that previously observed for ordered block copolymer solutions in neutral solvents, due to the solvent selectivity. The results are gathered in a rather rich phase diagram for this system.