TY - JOUR
T1 - Imaging liquid crystals dispersed in a ferroelectric polymer matrix by means of thermal-pulse tomography
AU - Suárez, Rosaura Flores
AU - Ganesan, Lakshmi Meena
AU - Wirges, Werner
AU - Gerhard, Reimund
AU - Mellinger, Axel
N1 - Funding Information:
The authors are indebted to the Liquid Crystals Divison of Merck KGaA in Darmstadt for kindly providing the LC samples investigated in this study. The authors are especially grateful to Dr. Brigitte Tiersch (University of Potsdam) for the SEM pictures. We thank the European Union for partial financial support of our laboratory within the ERDF program.
PY - 2010/8
Y1 - 2010/8
N2 - A new arrangement of the optical elements in a Thermal-Pulse-Tomography (TPT) setup allows to scan micrometer structures in composite and heterogeneous samples such as polymer-dispersed liquid crystals (PDLCs). The non-destructive TPT technique allows the determination of three-dimensional profiles of polarization and space charge in dielectrics. The samples under study were 12 m thick films of a copolymer of vinylidene fluoride with trifluoroethylene P(VDF-TrFE) (65/35) with embedded liquid-crystal droplets. The poling process was performed in direct contact well above the coercive field of the copolymer. The 3D map obtained from scanning with a 10 m wide spot shows elliptically shaped areas with liquid-crystal droplets. Considering the droplets as oblate spheroids, their major axis lies in the x-y plane, while their minor axis in the z direction measures 0.5 m or more. This result is in good agreement with scanning electron micrographs. It is believed that the major axis is overestimated due to imaging of liquid-crystal clusters.
AB - A new arrangement of the optical elements in a Thermal-Pulse-Tomography (TPT) setup allows to scan micrometer structures in composite and heterogeneous samples such as polymer-dispersed liquid crystals (PDLCs). The non-destructive TPT technique allows the determination of three-dimensional profiles of polarization and space charge in dielectrics. The samples under study were 12 m thick films of a copolymer of vinylidene fluoride with trifluoroethylene P(VDF-TrFE) (65/35) with embedded liquid-crystal droplets. The poling process was performed in direct contact well above the coercive field of the copolymer. The 3D map obtained from scanning with a 10 m wide spot shows elliptically shaped areas with liquid-crystal droplets. Considering the droplets as oblate spheroids, their major axis lies in the x-y plane, while their minor axis in the z direction measures 0.5 m or more. This result is in good agreement with scanning electron micrographs. It is believed that the major axis is overestimated due to imaging of liquid-crystal clusters.
KW - PDLC
KW - TPT
KW - Thermal-pulse tomography
KW - dielectrics
KW - nematic liquid-crystal
KW - polarization profile
KW - poly(vinylidene fluoride-co-trifluoroethylene)
KW - polymers
KW - pyroelectric effect
UR - http://www.scopus.com/inward/record.url?scp=77955581479&partnerID=8YFLogxK
U2 - 10.1109/TDEI.2010.5539683
DO - 10.1109/TDEI.2010.5539683
M3 - Article
AN - SCOPUS:77955581479
SN - 1070-9878
VL - 17
SP - 1123
EP - 1127
JO - IEEE Transactions on Dielectrics and Electrical Insulation
JF - IEEE Transactions on Dielectrics and Electrical Insulation
IS - 4
M1 - 5539683
ER -