Twist Grain Boundary Phases with Large Smectic Blocks, Commensurate Rotations and a SMC* Helix
Abstract
Three groups have previously observed TGB phases displaying a square or hexagonal grid structure when observed with polarized optical microscopy. Here we report freeze-fracture electron microscopy, polarized optical microscopy and x-ray scattering studies of materials from two of these groups. We found large smectic blocks (0.3 - 2.0 micron) that rotate along the TGB axis in a commensurate structure with 60 or 90 degree rotations between blocks. The smectic layer normal of each block is perpendicular to the TGB axis and the director structure within large blocks contains a SmC* helix (period 2 micron). Our observations are consistent with a theoretical model based on melted grain boundaries and large twist penetration within the smectic blocks. Work supported by NSF MRSEC Grant DMR 0213918 and ED GAANN Fellowship P200A000839.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARD22004F