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Title: Main-chain Chiral Smectic Polymers Showing a Large Electroclinic Effect in the SmA* Phase

Abstract

The synthesis and characterization of a main-chain smectic liquid-crystalline polymer system designed for development into electromechanical actuators is described. The chemical structure is chosen to provide a large electroclinic effect in the SmA* phase, with large concomitant layer shrinkage (a rare combination). The polymers are prepared by acyclic diene metathesis polymerization (ADMET) of liquid-crystalline ,-dienes. Oligomers with a degree of polymerization of {approx}10-30 are obtained using Grubbs first-generation catalyst, while oligomers with a degree of polymerization of {approx}200 are obtained using Grubbs second-generation catalyst. All polymer samples show the following phase sequence: I - SmA* - SmC* - Glass. X-ray analysis of polymer powder samples demonstrates the desired layer shrinkage at the SmA* - SmC* transition. The polymers form well-aligned fibers by pulling from the isotropic melt, and X-ray analysis of fibers in the SmA* phase shows that in the bulk of the fiber the layers are oriented perpendicular to the fiber axis, while at the surfaces there appears to be a thin sheath where the layers are parallel to the fiber/air interface. The desired layer shrinkage with tilt at the SmA* - SmC* transition in these fibers is seen as well, and in the SmC* phase the fibers exhibitmore » an interesting conical chevron layer structure. Electro-optic investigation of aligned thin films of the polymer, prepared from quenched fiber glasses using a novel technique, exhibit a large electroclinic effect, with substantial degradation of alignment quality upon field-induced tilt. This degradation in alignment quality, coupled with the layer shrinkage at the SmA* - SmC* transition demonstrated by X-ray scattering, strongly suggests the desired layer shrinkage with electroclinic tilt is in fact occurring in the polymer films.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930254
Report Number(s):
BNL-80946-2008-JA
Journal ID: ISSN 0897-4756; CMATEX; TRN: US200822%%1236
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 18
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; POLYMERS; SYNTHESIS; LIQUID CRYSTALS; ACTUATORS; FIBERS; ORIENTATION; PHASE TRANSFORMATIONS; ELECTRO-OPTICAL EFFECTS; THIN FILMS; SHRINKAGE; national synchrotron light source

Citation Formats

Walba,D., Yang, H., Shoemaker, R., Keller, P., Shao, r., Coleman, D., Jones, C., Nakata, M., and Clark, N. Main-chain Chiral Smectic Polymers Showing a Large Electroclinic Effect in the SmA* Phase. United States: N. p., 2006. Web. doi:10.1021/cm0606373.
Walba,D., Yang, H., Shoemaker, R., Keller, P., Shao, r., Coleman, D., Jones, C., Nakata, M., & Clark, N. Main-chain Chiral Smectic Polymers Showing a Large Electroclinic Effect in the SmA* Phase. United States. doi:10.1021/cm0606373.
Walba,D., Yang, H., Shoemaker, R., Keller, P., Shao, r., Coleman, D., Jones, C., Nakata, M., and Clark, N. Sun . "Main-chain Chiral Smectic Polymers Showing a Large Electroclinic Effect in the SmA* Phase". United States. doi:10.1021/cm0606373.
@article{osti_930254,
title = {Main-chain Chiral Smectic Polymers Showing a Large Electroclinic Effect in the SmA* Phase},
author = {Walba,D. and Yang, H. and Shoemaker, R. and Keller, P. and Shao, r. and Coleman, D. and Jones, C. and Nakata, M. and Clark, N.},
abstractNote = {The synthesis and characterization of a main-chain smectic liquid-crystalline polymer system designed for development into electromechanical actuators is described. The chemical structure is chosen to provide a large electroclinic effect in the SmA* phase, with large concomitant layer shrinkage (a rare combination). The polymers are prepared by acyclic diene metathesis polymerization (ADMET) of liquid-crystalline ,-dienes. Oligomers with a degree of polymerization of {approx}10-30 are obtained using Grubbs first-generation catalyst, while oligomers with a degree of polymerization of {approx}200 are obtained using Grubbs second-generation catalyst. All polymer samples show the following phase sequence: I - SmA* - SmC* - Glass. X-ray analysis of polymer powder samples demonstrates the desired layer shrinkage at the SmA* - SmC* transition. The polymers form well-aligned fibers by pulling from the isotropic melt, and X-ray analysis of fibers in the SmA* phase shows that in the bulk of the fiber the layers are oriented perpendicular to the fiber axis, while at the surfaces there appears to be a thin sheath where the layers are parallel to the fiber/air interface. The desired layer shrinkage with tilt at the SmA* - SmC* transition in these fibers is seen as well, and in the SmC* phase the fibers exhibit an interesting conical chevron layer structure. Electro-optic investigation of aligned thin films of the polymer, prepared from quenched fiber glasses using a novel technique, exhibit a large electroclinic effect, with substantial degradation of alignment quality upon field-induced tilt. This degradation in alignment quality, coupled with the layer shrinkage at the SmA* - SmC* transition demonstrated by X-ray scattering, strongly suggests the desired layer shrinkage with electroclinic tilt is in fact occurring in the polymer films.},
doi = {10.1021/cm0606373},
journal = {Chemistry of Materials},
number = ,
volume = 18,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
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