dc.contributor.advisor | Poon, Wilson | |
dc.contributor.advisor | Clegg, Paul | |
dc.contributor.author | Liddle, Siobhan Mary | |
dc.date.accessioned | 2014-11-18T15:00:05Z | |
dc.date.available | 2014-11-18T15:00:05Z | |
dc.date.issued | 2014-06-28 | |
dc.identifier.uri | http://hdl.handle.net/1842/9666 | |
dc.description.abstract | I have studied the effects of polydispersity in systems of hard-sphere, colloidal
PMMA particles with and without short-range attraction.
In hard-sphere, colloidal systems, the parameter controlling phase behaviour is Ø , the volume fraction of colloids in the solvent. As Ø increases in polydisperse
systems, theory predicts a transition from a single phase fluid to a fluid coexisting
with a solid (crystal), to a fluid coexisting with multiple solid phases. By
considering a volume fraction series of particles with 12% polydispersity and
comparing the results with previous experimental results and predictions of the
volume fractions within the coexistence regions, we concluded that this system
may be exhibiting both fluid-solid and fluid-solid-solid behaviour within the
experimental coexistence region.
Theory also predicts that coexisting phases in polydisperse hard-sphere systems
will fractionate: they will contain different particle size distributions (psds). This
was investigated by directly measuring psds for one sample within the coexistence
region at different time points. The results show that no statistically significant
size fractionation was present after 28 days but by 120 days the solid phase
contained a slightly narrower distribution of larger particles than the coexisting
fluid phase.
At higher than the coexistence region in this polydisperse system, the expected
coexisting solids are not observed. Instead, a novel, non-equilibrium phase
is present. The dynamics were probed using 3-dimensional dynamic light
scattering, which confirmed the non-equilibrium nature of the phase: significant
dynamical heterogeneities and anomalous ageing behaviour were present. These
experimental dynamics are compared with dynamics obtained from simulations of
different hard-sphere psds, including the experimental particle size distribution.
The effect of adding a short-range, depletion attraction to a polydisperse colloidal
system was systematically explored. Phase boundaries and the position of the
metastable gas-liquid binodal were determined experimentally. The resultant
phase diagram topology is qualitatively different to a system of monodisperse
particles with the same attraction range. Furthermore, within the metastable
binodal region, three-phase gas-liquid-solid samples were observed, which is
neither an equilibrium or metastable state in monodisperse systems. The
coexisting samples were again characterised using electron microscopy and also
small-angle x-ray scattering, which revealed significant size fractionation in the
gas-liquid separated samples but not in the samples which eventually crystallised. | en_US |
dc.contributor.sponsor | Engineering and Physical Sciences Research Council (EPSRC) | en_US |
dc.language.iso | en | en_US |
dc.publisher | The University of Edinburgh | en_US |
dc.relation.hasversion | Liddle, S. M., T. Narayanan, and W. C. K. Poon. "Polydispersity effects in colloidpolymer mixtures." Journal of Physics: Condensed Matter 23, 19: (2011) 194,116. doi: 10.1088/0953-8984/23/19/194116. | en_US |
dc.subject | polydispersity | en_US |
dc.subject | colloids | en_US |
dc.subject | fractionation | en_US |
dc.subject | frustrated fluid | en_US |
dc.title | Polydispersity effects on colloidal phase transitions and kinetic arrest | en_US |
dc.type | Thesis or Dissertation | en_US |
dc.type.qualificationlevel | Doctoral | en_US |
dc.type.qualificationname | PhD Doctor of Philosophy | en_US |