Effect of polarity of smectic A_d molecules on the induction of the nematic phase in binary mixtures of smectics A₁ and A_d

Abstract

The phase diagrams are determined of binary mixtures composed of 4-n-alkylbiphenylates 4-cyanobiphenyl (rz-CBB)-smectics A,, for rb < 8 and esters of 4-(trans-4'-n-alkylcyclohexy1)benzoic acid (lOCPCHB, lONPCHB, 1OFOPCHB)-smectics Ad.The effect is studied of the smectic layer spacing ratio and polarity of the components on the induction of the nematic phase in the tested series of compounds. The virtual N-Sad phase transition points in series n-CBB are estimated and the effect is discussed of the stability of the smectic phase and polarity of the molecules of the mixture components on the width and position of the nematic gap. Die Phasendiagramnie von biniiren, aus 4-cyanbiphenyl 4-alkylbiphenoaten (w-CBB)-smektischen Phasen und aus 4-(trans-4'-alkylcyclohexyl)benzoaten (IOCPCHB, IONPCHH, 1OFOPCHB)-smektischen Phasen Ad gebildeten Cemischen, wurden bestimmt.Es wurde der EinfluG des Dickenverhliltnisses der smektischen Schichten von Bestandteilen auf Induktionserscheinungen der nematischen Phase in der angegebenen Verbindungsserie untersucht. Die Temperaturen der virtuellen Phasenumwandlungen N-SA, in der Reihe n-CBB wurden geschgtzt. Der EinfluB der BestLndigkeit der smektischen Phase und des Gemisches auf Breite und Lage der nematisohen Phase wird diskutiert.

From the discovery of the partially bilayer smectic A phase to blue phases in polar liquid crystals

“…The lower is the polarity the more effective is the induction of SmA d phase. [138,140] In the mixture 7CBB-7OCB phase diagram as in Figure 6 (both the components are the last ones, wherein only the N phase is still present), the observed area of the induced SmA d phase is largein the mole ratio range of 8OCB = 0.1-0.8. The highest N-SmA d transition temperature is~264°C, the lowest SmA d -N re transition temperature is~20°C.…”

“…Compound C shows the SmA d -Iso transition (black curve a) and compound C1 shows the SmA d -N-Iso transition (red curve b). Examples of such pair of compounds are 5CBB or 6CBB or 7CBB with 10CPCHB or 10NPCHB or 10FOPCHB [138] and 5 or 6 or 7CBB with 8 or 9 or 10 or 12OCB or CB [139,140] and 5 or 6 or 7BCB with 10CN, [141] 7CBB-5EPCH and 7CBB with longer EPCH members. [43] The same character of phase diagram was observed for the three-ring compounds terminated with NCS or F or COCH 3 group in the bicomponent 10 R. Dąbrowski system 7CBB-10TPCHB or 7CBB-10FPCHB or 7CBB-10APCHB [142][143][144] and even for the tworing compounds terminated with NCS group in such bicomponent system as 7CBB-12DBT.…”