Smart self-organising systems attract considerable attention in the scientific community. In order to control and stabilise the liquid crystalline behaviour, and hence the self-organisation, the polymerisation process can be effectively used. Mesogenic units incorporated into the backbones as functional side chains of weakly cross-linked macromolecules can become orientationally ordered. Several new calamitic reactive mesogens possessing the vinyl terminal group with varying flexible chain lengths and with/without lateral substitution by the methyl (methoxy) groups have been designed and studied. Depending on the molecular structure, namely, the type and position of the lateral substituents, the resulting materials form the nematic, the orthogonal SmA and the tilted SmC phases in a reasonably broad temperature range, and the structure of the mesophases was confirmed by X-ray diffraction experiments. The main objective of this work is to contribute to better understanding of the molecular structure-mesomorphic property relationship for new functional reactive mesogens, aiming at further design of smart self-assembling macromolecular materials for novel sensor systems.

• Klíčová slova
• liquid crystal, reactive mesogen, self-assembling behaviour, smectic phases, vinyl group,
• Publikační typ
• časopisecké články MeSH

Thermotropic polyurethanes with mesogenic groups in side chains were prepared from two diisocyanates and four diols with stoichiometric ratios of reactive isocyanate (NCO) and hydroxy (OH) groups. Their thermal behavior was determined by differential scanning calorimetry. The effect of structure modifications of the diisocyanates and diols, in particular changes in the mesogen, were investigated. Introduction of mesogenic segments into the polymers suppresses the ordering. Stiff end substituents (phenyl and alkoxy groups) of the mesogens stabilize the mesophases to such an extent that the negative influence of long polymer chains is compensated and the liquid-crystalline properties are recovered. All-atom molecular dynamics simulations in the Cerius2 modeling environment were carried out to characterize the structures of the polymers. Analysis of the dynamic trajectories at 20, 100, 120 and 170 degrees C revealed changes in conformation of macromolecules, which correlate with DSC measurements.

• MeSH
• isokyanatany chemie   MeSH
• kalorimetrie MeSH
• molekulární konformace MeSH
• molekulární modely * MeSH
• molekulární struktura MeSH
• počítačová simulace MeSH
• polyurethany chemie   MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• isokyanatany MeSH
• polyurethany MeSH

Para-substituted 1-aryl-F-1,3-butadiene derivatives p-R-C(6)H(4)-CF=CFCF=CF(2) (2a-g), where R = H, CH(3), OCH(3), OC(6)H(11), N(CH(3))(2), Br, and CF(3), have been prepared by reaction of appropriate arylmagnesium bromides with F-1,3-butadiene. (19)F NMR chemical shifts correlate with sigma(p) Hammett substituent constants. Compounds 2a-e react on their terminal perfluorovinyl group with C-nucleophiles and were used as intermediates in subsequent reactions with suitable organolithium compounds for the synthesis of a new series of unsymmetrically substituted alpha,omega-diaryl-F-polyenes RC(6)H(4)(CF=CF)(n)()C(6)H(4)R', where n = 2 or 3 and R' is one of the substituents specified above. A variety of new synthons containing alpha,omega-diaryl-F-1,3-butadiene skeleton and reactive Br, OH, CH=O, and COOH functionalities in para-positions on aromatic rings has been also prepared. Structural aspects, NMR spectra, and mesogenic properties of the title compounds are discussed.

• Publikační typ
• časopisecké články MeSH