Ewa Białecka-Florjańczyk

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.

Studies on the lipolytic activity of sonicated enzymes from Yarrowia lipolytica

The aim of this study was to evaluate the efficiency of sonication in releasing protein from a widespread lipase-producing yeast, Yarrowia lipolytica KKP 379, and to examine the impact of ultrasound waves generated in a horn-type sonicator on the lipolytic activity of Y. lipolytica in the hydrolysis of p-nitrophenyl laurate. In this paper, we focused on a few parameters of ultrasound cell disruption, such as the time of sonication, acoustic power, storage time of the frozen yeast biomass used in sonication and the solvent used to suspend the yeast cells which were considered as the most important part in the process of obtaining a biocatalyst from Y. lipolytica for organic synthesis. The most effective additive in protein release proved to be 2% Tween 80; other ideal parameters of the process were ultrasonic power at 150 W for 15 min and 9 weeks of frozen biomass storage time. The sonication parameters, which were the best for protein release, did not seem to be the most effective for obtaining high lipolytic activity due to denaturation as an effect of cavitation.

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.

A Simple Method for the Preparation of Substituted Phenoxyacrylic Acid Phenyl Esters

Abstract A simple and efficient synthesis of phenoxyacrylic acid phenyl esters via one pot esterification and Michael-type addition starting from propynoic acid and an excess of an appropriate phenol is described.

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.

Comb-like polycarbosilanes-routes to a new group of liquid crystal polymers

Abstract Routes to two novel types of liquid crystal polycarbosilanes are described and preliminary studies of their properties are reported.

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.

Synthesis and Characterization of Liquid Crystalline Silsesquioxanes Containing Azobenzene Groups

Liquid crystalline silsesquioxanes having calamitic mesogenic and azobenzene moieties were synthesized by the hydrosilylation reaction of an inorganic silsesquioxane cube and terminal alkenes using Karstedts catalyst. Their chemical structures were confirmed by Fourier transform infrared (FTIR) and 1H- and 29Si-NMR (nuclear magnetic resonance) spectra. These oligomers have good thermostabilities, with the degradation process starting above 265°C. Their mesomorphic and phase behavior were investigated using differential scanning calorimetry (DSC), polarizing optical microscopy (POM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) measurements. The results show that the silsesquioxanes exhibit a broad range of liquid crystalline phases at moderate temperature. The ultraviolet (UV)-induced cis–trans photoisomerization was also studied for the liquid crystalline silsesquioxanes in chloroform.