Biographical
Information
Distinctions
and Awards
Selected
publications
D. Frenkel, H.N.W. Lekkerkerker and A.
Stroobants, Thermodynamic stability
of a smectic phase in a system of hard rods. Nature 332 (1988) 822 G.J. Vroege and H.N.W. Lekkerkerker, Phase transitions in lyotropic colloidal and polymer
liquid crystals. Rep. Prog. Phys. 55 (1992) 1241 H.N.W. Lekkerkerker, W.C.K. Poon, P.N. Pusey,
A. Stroobants and P.B. Warren, Phase
behaviour of colloid + polymer mixtures. Europhys. Lett. 20 (1992)
559 M.H.J. Hagen, E.J. Meijer, G.C.A.M. Mooij, D.
Frenkel H.N.W. Lekkerkerker, Does C60
have a liquid phase? Nature 365 (1993) 425 H.N.W. Lekkerkerker and A. Stroobants, Ordering entropy, News and views, Nature 393
(1998) 305 M.P.B. van Bruggen, J.K.G. Dhont and H.N.W.
Lekkerkerker, Morphology and kinetics of the isotropic-nematic phase
transition in dispersions of hard rods. Macromolecules 32
(1999) 2256 F.M. van der Kooij, K. Kassapidou and H.N.W.
Lekkerkerker, Liquid crystal phase transitions in suspensions of
polydisperse plate-like particles, Nature, 406 (2000), 868-871 H.N.W. Lekkerkerker and B. Widom, An exactly solvable model
for depletion phenomena, Physica A, 285 (2000) 483-492 E.H.A. de Hoog, W.K. Kegel, A. van Blaaderen
and H.N.W. Lekkerkerker, Direct observation of crystallization and aggregation
in a phase-separating colloid-polymer suspension Phys. Rev. E, 64
(2001) 021407-1 V.J. Anderson and H.N.W. Lekkerkerker, Insights into phase transition
kinetics from colloid science Nature,
416, (2002) 811-815 D.G.A.L. Aarts, M. Schmidt and H.N.W.
Lekkerkerker, Direct visual observation of thermal capillary
waves Science (2004) 304 847-850 The
study of the liquid crystal phase behavior of suspensions of rod-like and
plate-like colloids
We have developed new model systems for hard
colloidal rods and colloidal plates. The hard colloidal rods consist of a
Boehmite (AlOOH) core and a steric stabilization layer of polyisobutylene.
Dispersions of these particles show an isotropic-nematic phase separation.
Using polarization microscopy and small angle light scattering we observed
that depending on the concentration the pathway of phase separation is either
nucleation and growth or spinodal decomposition [1]. The effect of attractive
interactions on the phase behavior of colloidal rods has been studied by the
addition of non-adsorbing polymer. Now four pathways of phase separation can
be distinguished; nucleation and growth, spinodal decomposition aggregation
and gelation [2]. The hard colloidal plates we developed consist of a
Gibbsite (Al(OH)3) core and again a steric stabilization layer of
polyisobutylene. In dispersions of these particles we discovered an Isotropic
-Nematic [3] and Nematic-Columnar [4] phase transition. Especially the latter
transition is fascinating and unexpected as it persists for a polydispersity
up to 25%. Our results imply that liquid crystalline order in synthetic mesoscopic
materials may be easier to achieve than previously thought. We also
investigated the phase behavior of mixed dispersions of hard colloidal rods
and colloidal platelets. Here we were able to show experimentally that phase
separation in two coexisting uniaxial nematic phases occurs and not a single
biaxial nematic [5]. This issue has been the subject of considerable
theoretical debate. The
study of the phase behavior of mixed colloidal systems
We developed a theory of the phase behavior of
colloidal rod-sphere mixtures [6]. From this theory it follows that in such
systems a colloidal fluid colloidal crystal phase transition can occur at
very low concentrations of added colloidal rods. In subsequent experimental
work [7] we showed this indeed to be the case. At the same time we were able
to follow the morphology of the aggregation process that eventually leads to
crystallization [8]. The
study of interfaces in phase separated colloid polymer suspensions
Using the spinning drop method we were the first
to determine the ultra low interfacial tensions of the interface in a demixed
colloidal polymer system [9]. As predicted by simple scaling relations these
interfacial tensions are indeed as low as a few µN/m. We were able to confirm
this result by analyzing the rate of break up of long filamentous droplets.
Using ellipsometry we studied for the first time the interfacial profile
[10]. The thickness of the interfacial profile is of the order of the
diameter of the colloidal particles. 1. M.P.B. van Bruggen, J.K.G. Dhont and H.N.W. Lekkerkerker, Morphology and kinetics of the isotropic-nematic
phase transition in dispersions of hard rods, Macromolecules 32,
2256 (1999) 2. M.P.B. van Bruggen and H.N.W. Lekkerkerker, Tunable attractions directing nonequilibrium states in
dispersions of hard rods, Macromolecules, 33, 5532 (2000) 3. F.M. van der Kooij and H.N.W. Lekkerkerker, Formation of nematic liquid crystals in suspensions
of hard colloidal platelets, The Journal of Physical Chemistry B 102,
7829 (1998) 4. F.M. van der Kooij, K. Kassapidou and H.N.W. Lekkerkerker,Liquid crystal phase transitions in suspensions of
polydisperse plate-like particles, Nature, 406, 868 (2000) 5. F.M. van der Kooij and H.N.W. Lekkerkerker, Liquid-crystalline phase behavior of a colloidal
rod-plate mixture, Phys. Rev. Lett. 84, 781 (2000) 6. G.A. Vliegenthart and H.N.W. Lekkerkerker, Phase behavior of colloidal rod-sphere mixtures,
J. of Chem. Phys. 111, 4153 (1999) 7. G.H. Koenderink, G.A. Vliegenthart, S.G.J.M. Kluijtmans,
A. van Blaaderen, A.P. Philipse and H.N.W. Lekkerkerker, Depletion-induced crystallization in colloidal
rod-sphere mixtures, Langmuir 15, 4693 (1999) 8. G.A. Vliegenthart, A. van Blaaderen and H.N.W.
Lekkerkerker, Phase transitions,
aggregation and crystallization in mixed suspensions of colloidal spheres and
rods, Faraday Disc. 112, 173 (1999) 9. E.H.A. de Hoog and Henk N.W. Lekkerkerker, Measurement of the interfacial tension of a
phase-separated colloid-polymer suspension, Journal of Physical Chemistry
B 103, 5274 (1999) 10. E.H.A. de Hoog, H.N.W. Lekkerkerker, J. Schulz and G.H.
Findenegg, Ellipsometric study of the
liquid/liquid interface in a phase-separated colloid-polymer suspension,
The Journal of Phys. Chem. B. 103, 10657 (1999) |
