Date of Graduation
Statler College of Engineering and Mineral Resources
Mechanical and Aerospace Engineering
Darran R. Cairns.
In this dissertation I report on the successful fabrication of anisotropic liquid crystal polymer rods. These polymer rods demonstrated re-orientation by an applied external field. The polymer rods, 200 nm in diameter and a maximum of 60 mum in length, were produced by a template synthesis technique. A reactive liquid crystal monomer was filled into porous Anopore membranes which were used as a confining media. The liquid crystal monomer was polymerized by UV light while the liquid crystal remained in the nematic temperature range. The polymerization process permanently "freezes" the orientational order of the confined liquid crystal molecules, producing rods that are temperature independent after curing. The curing is kept in the nematic range to ensure proper orientational alignment in the pore of the membrane, where the responsive nature of the rods can be tailored by temperature, external fields, and/or surface treatments. The rods were suspended in low viscosity silicone oil and injected into indium tin oxide coated glass cells.;Both DC and AC electric fields were applied to the electro-optical glass cells, resulting in different types of rod movement. Switching times (time to change orientation from horizontal to vertical) has been observed to be as fast as 0.1 seconds and the threshold voltage has been as low as 5 volts. The switching times of the rods are mainly driven by the strength of the applied field and the molecular orientation of the rods. A model was used to describe the best case scenario of the rod structures and outlines that faster switching times are possible. Translational movement (moving vertical with the rod staying in the horizontal position) was also noted with the DC applied field. AC fields give different types of movement including rotational, vibrating, and swimming motions. The average rotational speed was found to vary linearly with the applied field strength, where the fastest speeds were at the highest field strength. Also, responsive rods were noted to move and push unresponsive rods in and out of the viewing area. The responsive rods are technologically important for possible electro-rheological fluids, magneto-rheological fluids, and components in microfluidic devices.
Shafran, Matthew S., "Responsive liquid crystal polymer rods" (2008). Graduate Theses, Dissertations, and Problem Reports. 1942.