New antiferroelectric liquid crystalline materials containing a keto group and two lactate groups

Effect of alkyl chains length on properties of ferroelectric liquid crystals with the keto group attached to the molecule core

“…The change of the non-chiral chain length has only a minor influence on mesomorphic properties, while the increase of the chiral chain length results in broadening of the SmA* and shift of the SmC* phase to the lower temperatures. Similar behaviour has been also observed for analogous materials possessing two chiral lactates [18]. The SmC* phase exist in a very broad temperature range which is more than 110 K broad for some of the studied compounds ( Table 1).…”

“…Using the keto group instead of the ether or ester groups for linking the alkyl chain with the molecular core also can lead to substantial increase in the values of spontaneous polarization as it was described by Yoschizawa et al [33] or Petrov [34]. Since that several series of the lactic acid derivatives [9] possessing the keto group as the linkage between the non-chiral chain and molecular core and with one [35,36], two [18,19,23] or three [17] lactate groups have been studied [9,17,37,38]. All these compounds possess the SmA* and SmC* phases over a broad temperature range.…”

“…The dielectric strength of the Goldstone mode, D" G , can be expressed by D" G % (1/8 2 K)(p P s / opt ) 2 [18,43], where K is an elastic constant. As no significant difference in polarization and tilt angle were observed among studied KL m/n compounds, only the difference in the helix pitch length could explain the remarkable difference between homologues in the values of the dielectric strength.…”

“…There are four main advantages of the lactic acid derivatives as a sub-class of chiral LCs that makes them attractive with respect to other materials, i.e. (i) forming of a broad variety of basic LC phases, including the cholesteric N*, paraelectric SmA* [10,11], ferroelectric SmC* [3,8,[12][13][14][15][16], antiferroelectric SmC Ã A [12,[17][18][19][20][21][22][23], polar hexatic phases [9,13,14,19,24] as well as frustrated ones like the twist grain boundary phases, namely TGB Ã A [1][2]7,12] and TGB Ã C [25] or SmQ* phase [12,26] or re-entrant SmA* [27][28][29] and re-entrant SmC* [9,13,24]; (ii) utilization of the lactic unit as a precursor of chiral centre minimizes the cost as the price ratio to the most commonly used chiral precursor material (S)-2-octanol is at least 1:100; (iii) melting points (m.p.) are often reasonable, in the range 30-70 C, and the LC phases can easily be supercooled well below room temperature and (iv) lactic acid-based LCs usually show no ageing, and are highly stable, thermally as well as chemically.…”

Mesomorphic andtrans–cis–transphotoisomerization studies of 4-[2-(4-hexyloxyphenyl)diazenyl]phenyl alkanoates

“…These types of compounds are synthesized in many research centres all over the world [9,10] and also in our group. [11] In recent time, mesogens containing such functional groups as keto moiety [12,13] and thioesters [14,15] have become more popular.…”