Pretransitional Behavior in the Isotropic Phase of Homologous Compounds Showing Nematic and Smectic C Type Order

Author(s):  
T. R. Steger ◽  
J. D. Litster ◽  
W. R. Young
2002 ◽  
Vol 117 (16) ◽  
pp. 7788-7792 ◽  
Author(s):  
Prabir K. Mukherjee ◽  
Harald Pleiner ◽  
Helmut R. Brand

1998 ◽  
Vol 10 (1) ◽  
pp. 147-153 ◽  
Author(s):  
M Tanaka ◽  
M Konda ◽  
M Miyamoto ◽  
Y Kimura ◽  
A Yamaguchi

Anomalous solid structures formed by a thermotropic liquid crystalline polyimide (PI-LC) were investigated by thermal analysis, polarized light microscopy and x-ray analysis. It was revealed that PI-LC should undergo a phase transition from the crystalline to the isotropic phase through the smectic or nematic phase in the temperature range 277–300 °C. The PI-LC filament extruded at 280 °C, at which temperature the polymer was in liquid crystalline phase, was formed to have a structure similar to the smectic C phase, while that extruded and melt-drawn at 310 °C, at which temperature the polymer was in the isotropic phase, had a structure similar to the smectic A phase.


1999 ◽  
Vol 559 ◽  
Author(s):  
C. Allan Guymon ◽  
Christopher N. Bowman ◽  
Christopher N. Bowman

ABSTRACTFerroelectric liquid crystals (FLCs) have shown great potential for use in electro-optic and display technology due to their inherently fast switching speeds and bistability. Recently, considerable research has been devoted to FLCs mechanically stabilized by a polymer network. The network is formed typically by in situ polymerization of a monomer dissolved in the FLC. Because of the inherent order in the FLC, the polymerization behavior may be significantly different than what might be expected in solution polymerizations. These deviations result largely from the segregation properties of the monomer in the liquid crystal. One class of monomers, namely fluorinated acrylates, is a likely candidate for inducing novel segregation, polymerization and electro-optic behavior in polymer stabilized ferroelectric liquid crystals (PSFLCs). The use of fluorinated moieties has a significant impact on the phase and polymerization behavior of liquid crystal systems. This study focuses on the polymerization of a fluorinated diacrylate, octafluoro 1,6-hexanediol diacrylate (FHDDA), to form PSFLCs and the consequent impact of the polymerization on the ultimate performance. Interestingly, as the temperature is increased and the order of the system decreases, a dramatic increase in the polymerization rate is observed. This increase is especially prominent for polymerizations in the smectic C* phase for which the rate is more than five times that exhibited at much higher temperatures in the isotropic phase. As with other monomer/FLC systems, the segregation of the monomer plays a role in this polymerization behavior as the monomer segregates between the smectic layers of the liquid crystal. The segregation properties also significantly impact the ultimate electro-optic properties. Both ferroelectric polarization and response time of the PSFLC change markedly with different polymerization temperatures, and approach values very close to those of the neat FLC under appropriate polymerization conditions. This behavior not only provides a unique mechanism for rate acceleration in PSFLCs, but also paves the way for new methods to optimize performance in these materials.


2013 ◽  
Vol 763 ◽  
pp. 37-40
Author(s):  
Chang Du ◽  
Nai Yu Zhou ◽  
Dan Liu ◽  
Fan Bao Meng

Chiral fluorinated side-chain liquid-crystalline elastomers (LCEs)IP-IVPwere graft copolymerized by hydrosilylation reaction. The chemical structure, liquid-crystalline behavior and polarization property were characterized by use of various experimental techniques. The effective crosslink density of the chiral LCEs was studied by swelling experiments. All the samplesIP-IVPdisplayed chiral smectic C mesophase (SC*) on heating and cooling cycles. With increasing chiral crosslinking units in the elastomer systems, the glass transition temperature and chiral smectic C mesophase-isotropic phase transition temperature of fluorinated elastomers increased slightly, indicating that the temperature range of SC*mesophase became narrow with increase of chiral crosslinking agents for all the chiral fluorinated elastomers. All the samplesIP-IVPshowed 0.12-0.16 μC/cm2of spontaneous polarization.


1995 ◽  
Vol 09 (13) ◽  
pp. 791-799 ◽  
Author(s):  
I. CUCULESCU ◽  
A. L. ALEXE-IONESCU ◽  
R. BENA ◽  
C. GHIZDEANU ◽  
V. STOIAN ◽  
...  

The transition temperatures from smectic C* to isotropic phase of a liquid crystal have been recorded as a function of an applied electric field. In addition to recent investigations on the phase transitions from smectic C* to smectic A in an electric field, we have found, in our case, a decrease of the transition temperature with the electric field. An explanation has been suggested to this behavior and a formula has been obtained which fits well the experimental points.


1987 ◽  
Vol 48 (8) ◽  
pp. 1241-1245 ◽  
Author(s):  
B.S. Andereck ◽  
B.R. Patton
Keyword(s):  

1993 ◽  
Vol 163 (10) ◽  
pp. 1 ◽  
Author(s):  
G.S. Chilaya ◽  
V.G. Chigrinov
Keyword(s):  

1990 ◽  
Vol 12 (4) ◽  
pp. 353-356 ◽  
Author(s):  
E. V Gevorkian ◽  
A. S Kashitsin ◽  
S. V Pasechnik ◽  
V. A Balandin

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