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A real-space study of phase behaviour and slow dynamics in colloid-polymer mixtures

Simple interactions in colloidal systems can often lead to complex phase behaviour and dynamics. In the work presented throughout this thesis, we study several related problems in colloid-polymer mixtures through real-space imaging, mainly through the use of confocal microscopy. We studied the phase separation dynamics in colloid-polymer mixtures crossing over from the regime of fluid-fluid phase separation into gelation. We related dynamics at the mesoscopic structural level to particle-level dynamics. Slow particle dynamics limited the rate of phase separation, and could lead to the arrest of phase separation and thus to gelation. The long-time stability and eventual collapse of colloidal gels were studied. We used a combination of microscopic and macroscopic imaging to observe both changes in the microstructure prior to collapse, and the sedimentation kinetics during collapse. Collapse timescales and collapse behaviour were linked to the phase behaviour and microstructure. The phase behaviour of a colloid-polymer mixture with bidisperse colloidal particles was studied and compared to the equivalent monodisperse systems. Multiple interaction ranges and strengths in the bidisperse system led to novel phase behaviour, including a near-critical region of the phase diagram where larger particles undergo phase separation but smaller particles remain in a one-phase state. Finally, self-assembly of clusters using particles with complementary shapes to promote site-specific bonding was attempted. Electrostatic charge was used to direct bonding in order to encourage the formation of linear clusters. While the formation of well-controlled structures was limited by kinetic effects, site-specific bonding appeared to be successful.
Date January 2014
CreatorsZhang, Isla
PublisherUniversity of Bristol
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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