Discotic Liquid Crystals and Polymersomes: Molecule Goniometers

Controlling the assembly of amphiphilic molecules and micron-sized, disk-shaped particles at different length scales into ordered structures enables bottom-up organization which is of great interest to emerging technologies based on structured materials. The primary object of this work is the investigation of structure forming components - Zirconium phosphate (ZrP) discotic particles and polymersomes/ amphiphiles on their self-assembly and interactions.

The effect of bilayer architecture of polymersomes on surface reactivity was investigated via fluorescent probing method. Established through complementary experiments, correlation between reactivity and molecule diffusivity in polymer-rich environment revealed the mechanism of reduced reactivity when tethered reactive groups are located deeper within the hydrophilic polymer layer.

The phase diagram of charged nanoplatelets was constructed as a function of particle concentration, surface cation moiety, and ionic strength. Influence of surface cation on the isotropic-nematic transition was done by measuring the transition boundaries of discotic suspensions prepared by acid-base exfoliation reaction with a series of exfoliating agents. Furthermore, a novel phase transition was found, where platelet-platelet interaction was influenced synergistically by ionic strength and ion exchange. At low pH, directional inter-platelet attractions lead to the formation of low volume fraction colloidal gels. Alternative surface modification approaches, including biomolecule deposition and alkyl chain grafting were explored.

Finally, self-assembly of platelets in emulsions and oil-water interface was examined. Surface modification was applied to link surface properties to stable emulsion-forming ability in mixed surfactant-particle system. Emulsion uniformity was achieved by microfluidic flow focusing method. Surface engineering and interaction control was demonstrated throughout this work to be viable approaches to the fundamental understanding of collective behaviors of individual building blocks.