Publications - 1997
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Recent advances in the study of chemical surfaces and interfaces by specular neutron reflection
J. Penfold, R.M. Richardson, A. Zarbakhsh, J.R.P. Webster, D.G. Bucknall, A.R. Rennie, R.A.L. Jones, T. Cosgrove, R.K. Thomas, J.S. Higgins, P.D.I. Fletcher, E. Dickinson, S.J. Roser, I.A. McLure, A.R. Hillman, R.W. Richards, E.J. Staples, A.N. Burgess, E.A. Simister and J.W. White
ISIS Facility, Rutherford Appleton Laboratory, Oxfordshire, Chilton, Didcot, UK
J. Chem. Soc., Faraday Trans. (1997), 93(22), 3899-3917
Abstract
The use of specular neutron reflection to study a wide variety of problems in surface and interfacial chem. is introduced and discussed. Recent developments in neutron reflectometry instrumentation, and their implementation in the design of the SURF reflectometer at the ISIS pulsed neutron source, are described. The design of the SURF reflectometer has been optimized for the surface chem. of soft matter and new exptl. results that exploit the novel features of this second generation neutron reflectometer are presented and discussed in the context of the opportunities for future studies that the technique and the new instrumentation presents. The examples from the broad program in surface chem. include surfactant and polymer adsorption at the air/liq. and liq./solid interfaces, adsorption at the liq./liq. interface; Langmuir-Blodgett films and liq. cryst. alignment layers, thin solid polymer films and interfaces; liq. mixts. and in situ electrochem. 104 Refs.
The use of block copolymer stabilizers for controlling dispersion stability
T. Cosgrove
School of Chemistry, University of Bristol, Bristol, UK
Int. J. Cosmet. Sci. (1997), 19(4), 157-166
Abstract
The role of block copolymers in stabilizing colloidal dispersions against flocculation or coalescence is discussed in terms of the detailed structure of the interface. Both particulate dispersions and liq./liq. interfaces are used as examples. Two novel exptl. methods are introduced, small-angle neutron scattering and neutron reflection. Comparison with the Scheutjens Fleer theory for block copolymers is also presented. Strategies for the optimum design of the stabilizing polymer are introduced.
The adsorption of polydimethylsiloxane onto silica from the melt
Terence Cosgrove, Michael J. Turner and David R Thomas
School of Chemistry, University of Bristol, Bristol, UK
Polymer (1997), 38(15), 3885-3892
Abstract
N.m.r. relaxation and diffusion studies of the adsorption of polydimethylsiloxane polymers on silicas have been carried out as a function of particle concn. and polymer mol. wt. The structure of the adsorbed layer can be rationalized by a three-state model comprising bound polymer, polymer entangled or restricted by the adsorbed layer and free bulk polymer. In particular, n.m.r. relaxation and diffusion studies have enabled us to describe these regions quant. At a loading of 10% particles, nearly 90% of the polymer segments in the dispersion have their mobility constrained, though only .apprx.10% of these segments belong to chains that are adsorbed. The diffusion of the bulk polymer is also affected by the inclusion of particulates, and the overall mobility is reduced.
Structure of Sodium Dodecyl Sulfate Bound to a Poly(NIPAM) Microgel Particle
S.J. Mears, Y. Deng, T. Cosgrove and R. Pelton
School of Chemistry, University of Bristol, Bristol, UK
Langmuir (1997), 13(7), 1901-1906
Abstract
Dynamic light scattering, small-angle neutron scattering, and binding isotherm measurements have been performed on an aq. poly(N-isopropylacrylamide) microgel particle in the presence of the surfactant sodium dodecyl sulfate (SDS). In the presence of the microgel, at concns. just above the normal cmc the surfactant existed as small, polymer-bound aggregates of less than five monomer units rather than larger micelles. This is in stark contrast to other homopolymer/surfactant systems such as SDS/poly(ethylene oxide) where the polymer-bound micelles have structures similar to those of free micelles obtained without polymers. Both dynamic light scattering and small-angle neutron scattering measurements showed that the microgel swells in the presence of surfactant. Two surfactant concns. (1% wt./wt. and 0.3% wt./wt.) were used for the neutron scattering expts., and through selective deuteration of the solvent, the different components, either the poly(N-isopropylacrylamide) gel or the SDS, were rendered 'invisible' to the neutrons.
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