Page 28 - ILLS Annual Report 2018

SOFT MATTER
Patrick Guenoun. French
Laboratoire Interdisciplinaire sur l’Organisation Nanométrique et Supramoléculaire (LIONS)
at Université Paris-Saclay (CEA Saclay)
‘My research belongs to the experimental
soft condensed matter area, focusing on polymers at interfaces for controlling emulsion
stabilisation, the orientation of nanocomposites made of plasmonic nanoparticles and copolymer blocks, and omniphobic wetting properties.’
Neutron reflectivity measurements at the oil-water interface for studying stimuli-responsive emulsions
Fluid interfaces grazing angles reflectometer FIGARO
Emulsions are metastable dispersed phases of either oil drops in water (direct emulsions O/W), water drops in oil (inverse emulsion W/O) or even water drops nested in oil drops in water (multiple emulsions, W/O/W). We developed a system based on
an emulsion superior stabilisation
by a single amphiphilic copolymer PS-b-(PS-stat-PDMAEMA made
of polystyrene (PS) and poly(dimethylaminoethyl methacrylate) (PDMAEMA) moieties. It is capable of stabilising the three kinds of emulsions depending on certain strength conditions [1]. Our system is therefore unique in elucidating how amphiphile conformation is related to emulsion type. This is important for providing molecular guidelines aimed at designing future polymeric emulsions, since these phases are currently used in many applications of encapsulation in pharmacy,
food and the cosmetic industry.
AUTHORS
P. Guenoun (University Paris-Saclay, CEA Saclay, France)
M. Protat, N. Bodin-Thomazo and F. Malloggi (CEA, CNRS, University Paris-Saclay, France)
J. Daillant (Synchrotron Soleil, Saint-Aubin, France)
R.A. Campbell (Division of Pharmacy and Optometry, University of Manchester, UK)
G. Fragneto and E.B. Watkins (ILL)
P. Perrin and N. Pantoustier (ESPCI Paris, PSL University, Sorbonne-University, CNRS, France)
ARTICLE FROM
Eur. Phys. J. E (2018)—doi: 10.1140/epje/i2018-11693-8
REFERENCES
[1] L. Besnard, F. Marchal, J.F. Paredes, J. Daillant, N. Pantoustier, P. Perrin and P. Guenoun, Adv. Mater. 25 (2013) 2844
[2] R.A. Campbell, H.P. Wacklin, I. Sutton, R. Cubitt and G. Fragneto, Eur. Phys. J. Plus 126 (2011) 107
[3] L.T. Lee, D. Langevin and B. Farnoux, Phys. Rev. Lett. 67 (1991) 2678
[4] M. Protat, N. Bodin-Thomazo, F. Malloggi, J. Daillant, R.A. Campbell, F. Fragneto, E.B. Watkins, P. Perrin, N. Pantoustier and P. Guenoun, Eur. Phys. J. E 41 (2018) 85
A tool of choice for providing insight into this conformation is neutron reflectometry [2]. However, neutron reflectivity measurements at liquid/liquid interface are rarely performed and have been limited to date to a few particular examples [3]. A dedicated cell was designed and optimised for such a study, with systems in which the oil phase scatters a large number of neutrons because
of the dissolved polymer. A sapphire crystal is used in support of a water phase, through which the neutron beam reaches the interface, yet the need to match the water phase’s isotopic contrast with that of the sapphire means that it is still partly hydrogenous (10 % v/v H2O in D2O) and must be reduced to minimal thickness (figure 1). This is possible thanks to the high flux FIGARO (Fluid Interfaces Grazing Angles ReflectOmeter) reflectometer, which has the ability to reflect a collimated beam of neutrons down at a horizontal interface. A particularly high flux configuration can be selected thanks to the use of dephased choppers and the instrument being on a continuous reactor source.
Figure 1
Scheme of the liquid/liquid cell and incident neutron beam. The black part to the left is used for sucking water and modifying the level, while the white Teflon parts are also indicated. Adsorbed polymer chains are indicated on the sapphire (made hydrophilic by plasma cleaning beforehand) and their contribution is taken into account in the data treatment. The main signal comes from the chains adsorbed at the oil-water interface.
ANNUAL REPORT 2018