Design of photonic liquid crystal materials: synthesis and evaluation of new chiral thioindigo dopants designed to photomodulate the spontaneous polarization of ferroelectric liquid crystals
作者:Liviu Dinescu、Kenneth E. Maly、Robert P. Lemieux
DOI:10.1039/a903052b
日期:——
Irradiation of a ferroelectric S
C
* liquid crystal phase induced by the photochromic dopants (R,R)-6,6′-bis(2-octyloxy)-5,5′-dinitrothioindigo and (R,R)-5,5′-dichloro-6,6′-bis(2-octyloxy)thioindigo at λ=514 and 532 nm, respectively, causes an increase in spontaneous polarization (P
S
) by a factor ranging from 1.4 to 4.0. This increase in P
S
is achieved without concomitant destabilization of the S
C
* phase, and is consistent with an increase in transverse dipole moment of the thioindigo core as a result of trans-cis photoisomerization. The contribution of the thioindigo core towards P
S
is achieved through stereo-polar coupling with the chiral side-chains, which is enhanced by the presence of the nitro and chloro substituents.
由光致变色掺杂物 (R,R)-6,6′-bis(2-octyloxy)-5,5′-dinitrothioindigo 和 (R,R)-5,5′-dichloro-6,6′-bis(2-octyloxy)thioindigo 在波长 λ=514 和 532 nm 下照射,引起了铁电 S C * 液晶相自发极化 (P S ) 的增加,增幅范围从 1.4 到 4.0。P S 的这种增加是在不伴随 S C * 相不稳定化的情况下实现的,且与因顺-反光异构化导致的硫靛核心的横向偶极矩增加相一致。硫靛核心对 P S 的贡献是通过与手性侧链的立体极化耦合实现的,该耦合在硝基和氯取代基的存在下得到了增强。