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SUMMARY:Oppositely Charged Polyelectrolyte/Surfactant Mixtures at  the Air
 /Water Interface: The Dominance of Non-equilibrium Effects  - Dr Richard A
  Campbell\, University of Manchester
DTSTART:20181025T103000Z
DTEND:20181025T113000Z
UID:TALK109777@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:Oppositely charged polyelectrolyte/surfactant mixtures control
  the properties of many of the consumer products that we use in our everyd
 ay lives. While work has been carried out to understand the properties of 
 these mixtures under dynamic conditions relevant to processing and applica
 tions [1–2]\, there is a growing awareness that also the static properti
 es of such mixtures are strongly influenced by non-equilibrium effects [3
 –4]. We have worked over the last years to relate the interfacial proper
 ties of these systems to different non-equilibrium processes in the bulk a
 nd at interfaces [5–13]. \n In this seminar\, it is described how non-eq
 uilibrium effects not only influence but in fact dominate the interfacial 
 properties of such mixtures. Our work focuses on the strongly interacting 
 systems Pdadmac/SDS* and NaPSS/DTAB** measured using a range of bulk and s
 urface-sensitive techniques including neutron reflectometry\, ellipsometry
  and Brewster angle microscopy. With an initial focus on the surface tensi
 on behaviour\, it is shown that these materials inevitably exist out of eq
 uilibrium conditions for a prolonged period due to very slow equilibration
  of the bulk\, even if steady state interfacial properties can be measured
  in the meantime. The situation is further complicated by the formation of
  liquid crystalline particles in the bulk that can resist dissolution upon
  chemical change. Their formation depletes the solution yet their penetrat
 ion into the interfacial layer – shown to be mediated by different paral
 lel processes such as surface affinity\, kinetic trapping and transport un
 der gravity – enhances the interfacial properties. These interfacial int
 eractions can result in dissociation of the particles and the spreading of
  material by Marangoni flow to form a trapped film. We are currently explo
 iting this mechanism to form films that are more efficient that adsorbed l
 ayers form the bulk. \n The intricacy of the problem\, even for relatively
  simple mixtures\, is quite astounding\, and the presented framework provi
 des a platform on which to develop understanding of the actual behaviour o
 f more complex mixtures used in industry and present in nature. \n * poly(
 diallyldimethylammonium chloride)/sodium dodecyl sulfate ** poly(sodium st
 yrene sulfonate)/dodecyltrimethylammonium bromide \n \n[1] R. A. Campbell 
 et al. Langmuir 2007\, 23\, 3242. [2] B. A. Noskov et al. Langmuir 2007\, 
 23\, 9641. [3] R. Mészáros et al. Langmuir 2003\, 19\, 609. [4] A. Nader
 i et al. Colloids Surfaces A 2005\, 253\, 83. [5] R. A. Campbell et al. J.
  Phys. Chem. Letters 2010\, 1\, 3021. [6] R. A. Campbell et al. J. Phys. C
 hem. B 2011\, 115\, 15202\, [7] R. A. Campbell et al. J. Phys. Chem. B 201
 2\, 116\, 7981. [8] Á. Ábraham et al. Langmuir 2013\, 29\, 11554. [9] Á
 . Ábraham et al. Langmuir 2014\, 30\, 4970. [10] R. A. Campbell et al. La
 ngmuir 2014\, 30\, 8664. [11] R. A. Campbell et al. Soft Matter 2016\, 12\
 , 5304. [12] I. Varga et al. Langmuir 2017\, 33\, 5915. [13] Tummino et al
 . Langmuir 2018\, 34\, 2312. 
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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