Liquid crystals for IR: Part I – synthesis and properties of perfluoroalkyl or perfluoroalkoxy terminated oligophenyls

Abstract

Synthesis procedures2-[4-(trifluoromethoxy)phenyl]-1,3,2-dioxaborinane 3 The solution of 1-bromo-4-(trifluoromethoxy)benzene 1(363g -1.50mol)in 1500cm 3 of anhydrous THF was added dropwise to magnesium chips (36.1g -1.50mol) with vigorous stirring under an N2 atmosphere. After addition, the reaction mixture was refluxed for 1h, then it was cooled slowly to room temperature and then to −70 o C. Maintaining vigorous stirring, tripropyl boronate B(OC3H7)3 (311.5g -1.65mol) was added dropwise. Stirring was continued while the mixture was allowed to heat up to roomtemperature. Then the solvents were evaporated andthe residue was acidified with 150cm 3 38% HCl and 150cm 3 H2O. Due to the problem with separation of boronic acid it was decided to convert it into cyclic ester (1,3,2dioxaborinane) with propane-1,3-diol. To obtain suspension 1000cm 3 toluene and propane-1,3diol (114g -1.5mol) was added and it was heat up to the boiling temperature. During reaction water was removed by azeotropic distillation. Reaction mixture was poured into 500cm 3 H2O. Crude product was extracted with toluene. Organic layer was washed three times with water, separated, dried with MgSO4 and solvent evaporated. Product was distilled under reduced pressure b.p. 111-112 o C at 0.6 mmHg, yield 258g (70%). MS(EI) m/z: 246(M+); 188; 175; 69. 1

New-Generation Liquid Crystal Materials for Application in Infrared Region

“…As described in previous works [ 57 , 58 , 59 ] in the case of mesomorphs dedicated to infrared applications, where short perfluorinated chains are used, the presence of liquid crystalline phases is mainly related to the structure of the core itself. Functionalization in the lateral position helps to fine-tune expected parameters such as mesophase morphology, temperature range, and clearing and melting temperatures.…”

“…THF was distilled from sodium under nitrogen atmosphere prior to use. 2-(4-(Trifluoromethoxy)phenyl)-1,3,2-dioxaborinane, 2-(3-fluoro-4 (trifluoromethoxy)phenyl)-1,3,2-dioxaborinane, and 2-(3,5-difluoro-4-(trifluoromethoxy)phenyl)-1,3,2-dioxaborinane were synthesized in our laboratory; all the details of the synthesis and purification process are described in [ 58 ]. 1-Ethynyl-4-(trifluoromethoxy) benzene, 4-ethynyl-2-fluoro-1-(trifluoromethoxy) benzene, and 5-ethynyl-1,3-difluoro-2-(trifluoromethoxy) benzene were synthesized in our laboratory; all the details of the synthesis and purification process are described in [ 57 ].…”

“… Spectral properties in the range of 2–6 μm for selected compounds: terphenyl (in black) [ 57 ], phenyltolane (in red) [ 58 ], 13b (in blue), 18c (in green), and 5CB (in orange). …”

“…On the other hand, when the fluorine atom was in the inner core position (18d), the compound exhibited only a smectic phase in a very wide range (129.1 • C) and even lower melting point. Further introduction of the fluorine atom in the outer core position (18c) caused the complete disappearance of the smectic phase, lowering the melting point and narrowing the range of the nematic phase by 13.5 • C.Figure12shows the influence of the core structure on the mesomorphic properties.As described in previous works[57][58][59] in the case of mesomorphs dedicated to infrared applications, where short perfluorinated chains are used, the presence of liquid crystalline phases is mainly related to the structure of the core itself. Functionalization in the lateral position helps to fine-tune expected parameters such as mesophase morphology, temperature range, and clearing and melting temperatures.…”

“…As part of our previous work [ 57 , 58 , 59 ], we developed a new molecular design approach that allowed us to obtain a next-generation self-assembling material primarily for use in the infrared range, and particularly in the MWIR range [ 60 , 61 , 62 , 63 ]. This approach involved shifting parasitic absorption bands toward longer wavelengths.…”