Irma Śledzińska

Odd–even effect in biphenyl‐based symmetrical dimers with methylene spacer – evidence of the B4 phase

A series of 4‐decyloxy‐4′‐hydroxybiphenyl esters of α,ω‐alkanedicarboxylic acids containing two mesogenic units connected by a methylene spacer was synthesized. The mesogenic properties of the compounds were investigated by polarising optical microscopy, differential scanning calorimetry and X‐ray diffraction methods. A strong influence of the spacer length and its parity on the mesomorphic properties was found. A dramatic odd–even effect was observed for the clearing temperatures and entropies. Compounds with an even number of carbon atoms in the methylene spacer formed tilted smectic phases, whereas compounds with an odd number of carbon atoms in the spacer exhibited the B4 phase, characteristic of bent‐shaped molecules.

Synthesis and liquid crystalline properties of cholesteryl bisesterimides with poly(ethylene oxide)s as central spacers

Abstract A number of new symmetric dimers comprising cholesteryl esterimide groups connected through a poly(ethylene oxide) chain have been synthesized and studied by means of polarized optical microscopy, DSC and X-ray diffraction methods. The smectic C phase has been observed for dimers up to n = 34 of the average number of oxyethylene units in the spacer. The dimers with the spacers containing n ≤ 9 oxyethylene units form chiral nematic N∗ and smectic C phases. It was found that a coupling of the cholesteryl esterimide groups into dimers promotes mesomorphic behaviour.

Validation of chromatographic retention models in reversed-phase high-performacne liquid chromatography by fitting experimental data to the relevant equations

Abstract Capacity factors ( k ′) were measured for five steroid hormones in the binary mobile phases methanol-water and acetonitrile-water as a function of methanol and acetonitrile concentration. The results were interpreted in terms of five models of chromatographic retention selected from the many that have been published. The R factor statistic based on the F distribution was used for testing th goodness of fit of the models to the experimental data.

Synthesis and characterization of liquid crystal polycarbosilanes: poly(1-methyl-1-silaethylene), poly(1-methyl-1-silabutane) and poly(1-silabutane) with pendant mesogenic groups

Abstract The synthetic routes for preparation of side chain liquid crystal polycarbosilanes, with rod type mesogens, pending from every second and every fourth atom in the main chain, forming ‘comb-like’ and ‘double comb-like’ polymers, are described. Structure—property relationships were investigated. X-ray measurements of the smectic materials, oriented in a magnetic field, proved the S A1 phase to be a dominant one for these new mesomorphic polymers; however, generation of S Ad and more ordered S B phases was also detected. Polycarbosilanes present useful, highly thermally and chemically resistant materials, which provide useful models for studies of the influence of the main chain architecture on the properties of polymers with various pendant groups.

Liquid crystal dimers with organosilicon spacers as models for side chain LC polymers

Abstract A series of six mesogenic dimers were prepared containing terminal 4’-methoxyphenyl-4-octenyloxybenzoate groups, of the general formula [MeOC 6 H 4 O(O)CC 6 H 4 O(CH 2 ) 8 SiMe 2 ] 2 R, where R=–CH 2 –, –(CH 2 ) 2 –, –(CH 2 ) 3 –, –SiMe 2 –, –O– and –NH–. Their liquid crystal properties were compared with those of the structurally relevant side chain polymers with the same mesogenic moiety: polycarbosilanes, polyethylene, and polysiloxane. It is shown that the low molecular dimers can be used as models for evaluating and predicting mesogenic characteristics of macromolecular systems with backbones structurally equivalent to spacers of the dimers.

Evidence of the smectic antiphase in 4-decyloxybiphenyl ester imide derivatives

The series of liquid crystalline 4-[(4′-decyloxybiphenyl-4-yl)oxycarbonyl]phthalimide alkane acid methyl esters has been synthesized and studied by DSC, polarized optical microscopy and X-ray diffraction methods. All compounds form a monolayer smectic A phase. It was found that 2-{4-[(4′-decyloxybiphenyl-4-yl)oxycarbonyl]-phthalimido}propanoic acid methyl ester and 4-[(4′-decyloxybiphenyl-4-yl)oxycarbonyl]phthalimidoacetic acid methyl ester also form a ribbon S phase. It was shown clearly that in the former compound, transition from the S A1 to S phase occurs via an intermediate S C1 phase. The 6-{4-[(4′-decyloxybiphenyl-4-yl)oxycarbonyl]phthalimido}-hexanoic acid methyl ester exhibits smectic A 1 and C 1 phases only.

Studies on the liquid crystalline behaviour of novel N-alkyl-substituted ester imides

Three new series of N-alkyl-substituted ester imide derivatives, which differ in the polarity of their mesogenic groups; specifically, either cholesteryl, 4′-undecyloxybiphenyl or 4′-cyanobiphenyl, have been synthesized. For the N-alkyl-[4-(cholesteryloxycarbonyl)]phthalimides the chiral nematic N* phase and the monolayer SmA1 phase have been observed up to the dodecyl homologue. The pentadecyl and octadecyl members of this series show only the SmA1 phase. The monolayer smectic A1 phase was also observed for all members of the N-alkyl-4-[(4′-undecyloxybiphenyl-4-yl)oxycarbonyl]phthalimide series while the longer homologues (with n>5) exhibited SmA–SmC dimorphism. In the case of the N-alkyl-4-[(4′-cyanobiphenyl-4-yl)oxycarbonyl]phthalimides, the short homologues exhibited only a nematic phase, while for the butyl homologue in addition to the nematic phase the bilayered SmA2 phase was observed. The smectic phase vanished for the pentyl and hexyl members but reappeared as a partially bilayered smectic Ad phase for the longer homologues.

The influence of structural changes of symmetrical dimers containing two phenyl groups on liquid crystalline behaviour

Some symmetrical dimeric compounds containing biphenyl, biphenylcarboxylic acid or benzoiloxyphenyl moieties and polymethylene spacers were synthesised. The mesogenic properties of the synthesised compounds were investigated by optical microscopy, calorimetric and X-ray methods. It was shown that the location and direction of the ester bonds has a crucial significance in mesophase formation.

Cholesteryl esterimides with oxyethylene and methylene tails

Abstract Two series of liquid crystalline systems comprising [4-(cholesteryloxycarbonyl) phtalimide] acetic acid esters of several poly(ethylene glycol) methyl ethers or aliphatic alcohols have been synthesized and studied by means of DSC, polarized optical microscopy and X-ray diffraction methods. All compounds form the chiral nematic phase N*. It was found that the esterimides with oxyethylene tails form additionally the chiral smectic C* phase. Its layer distances show a bilayer stacking likely to result from microsegregation among polar and nonpolar parts of the molecules. In the case of mesogens with methylene tails the monolayer smectic A phase has been observed.

The influence of structural changes of the N‐substituent on liquid crystalline behaviour of ester imides

Several new ester imide derivatives with different N‐substituents in the imide ring were synthesized and their mesogenic properties investigated by thermal analysis, optical microscopy and X‐ray diffraction. All the esters of N‐4‐[(4′‐decyloxybiphenyl‐4‐yl)oxycarbonyl]phthalimideacetic acid and aliphatic alcohols exhibited monolayer SmA and SmC phases. In addition, for the ethyl and propyl esters a monotropic hexatic (F or I) phase was observed. The introduction of additional substituents at the carbon atom in the methylenemethoxycarbonyl group (in the vicinity of the nitrogen atom) substantially influenced liquid crystalline properties: the compounds with a flexible chain exhibited monotropic SmA–SmB dimorphism, but liquid crystalline properties vanished for the substituent containing the more rigid phenyl ring.