X-ray study of liquid crystal alignment films and discotic liquid crystal strands.

Format:

Book

Thesis/Dissertation

Author/Creator:

Ghosh, Surya S.

Contributor:

Heiney, Paul A., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Condensed matter.

Solid state physics.

0611.

Penn dissertations--Physics.

Physics--Penn dissertations.

Penn dissertations--Astronomy.

Astronomy--Penn dissertations.

Local Subjects:

Penn dissertations--Physics.

Physics--Penn dissertations.

Penn dissertations--Astronomy.

Astronomy--Penn dissertations.

0611.

Physical Description:

147 pages

Contained In:

Dissertation Abstracts International 58-11B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

We present x-ray diffuse scattering measurements from freely-suspended strands of discotic liquid crystals, and x-ray reflectivity measurements of polyimide films on glass. The diffuse scattering measurements are the first quantitative measurements of the diffuse scattering from a discotic-hexagonal phase. We report a toroid of diffuse scattering in the basal plane, consisting of constant-$\vert$Q$\vert$ arcs surrounding the Bragg $$ points. The toroid has an anisotropic cross-section in the HOL plane, and exhibits a surprising sinusoidal variation in intensity as the $\phi$-angle is varied. We compare our results to the diffuse scattering expected from phonons in the discotic-hexagonal phase.

We also report x-ray reflectivity measurements of mechanically rubbed polyimide films and dye-doped polyimide films that have been exposed to linearly-polarized laser light. We find anisotropic off-specular diffuse scattering in the mechanically rubbed films, which we attribute to grooves created by the rubbing process. Our x-ray reflectivity analysis suggests that the optically "aligned" dye-doped polyimide film has laterally distributed regions which are slightly thicker and much less electron-dense than the surrounding polyimide. An anisotropic roughness has been measured suggesting that these regions have some alignment. We suggest that the molecular-scale anisotropy in these regions gives clues to the mechanism of nematic liquid crystal alignment on the dye-doped optically "aligned" polyimides.

Notes:

Thesis (Ph.D. in Physics and Astronomy) -- University of Pennsylvania, 1997.

Source: Dissertation Abstracts International, Volume: 58-11, Section: B, page: 6024.

Supervisor: Paul A. Heiney.

Local Notes:

School code: 0175.

ISBN:

9780591659313

Access Restriction:

Restricted for use by site license.