Supermolecular chiral mesogenic tripedes.

A novel series of chiral liquid crystalline tripedes Glucoside and Mannoside derivatives G(n) and M(n) (n=1-3) have been synthesised. The inner cores consist of methyl α-D-Glucoside G or methyl α-D-Mannoside M, regioselectively functionalised at the less hindered position C6, with tert-butyldimethylsilyl (TBDMS), hydroxyl or carboxylic acid moieties. The cores, which can acquire several flexible conformations, are attached to rod-like smectogenic-preferring cyanobiphenyl units, by means of a flexible hexanoyl spacer. These Glyco-Supermolecules exhibit chiral nematic (N*) and smectic A (SmA) phases. The combined effects of core chirality and functional groups on thermal and mesomorphic characteristics are discussed.

Optically active liquid-crystalline fullerodendrimers from enantiomerically pure fulleropyrrolidines.

A synthetic methodology based on the 1,3-dipolar cycloaddition reaction was developed to design enantiomerically pure liquid-crystalline fullerodendrimers.

Liquid-crystalline aromatic-aliphatic copolyester bioresorbable polymers.

The synthesis and characterisation of a series of liquid-crystalline aromatic-aliphatic copolyesters are presented. Differential scanning calorimetry showed these polymers have a glass transition temperature in the range 72 degrees C-116 degrees C. Polarised optical microscopy showed each polymer exhibits a nematic mesophase on heating to the molten state at temperatures below 165 degrees C. Melt processing is demonstrated by the production of injection moulded and compression moulded specimens with Young's modulus of 5.7 +/- 0.3 GPa and 2.3 +/- 0.3 GPa, respectively. Wide-angle X-ray scattering data showed molecular orientation is responsible for the increase of mechanical properties along the injection direction. Degradation studies in the temperature range 37 degrees C-80 degrees C are presented for one polymer of this series and a kinetic constant of 0.002 days(-1) is obtained at 37 degrees C assuming a first order reaction. The activation energy (83.4 kJ mol(-1)) is obtained following the Arrhenius analysis of degradation, showing degradation of this material is less temperature sensitive compared with other commercially available biodegradable polyesters. In vitro and in vivo biocompatibility data are presented and it is shown the unique combination of degradative, mechanical and biological properties of these polymers may represent in the future an alternative for medical device manufacturers.

Diastereoisomerically pure fulleropyrrolidines as chiral platforms for the design of optically active liquid crystals.

Incorporation of [60]fullerene (C(60)) within self-organizing systems is conceptually challenging but allows us to obtain materials which combine the characteristics (anisotropy, organization) of condensed mesophases with the properties of C(60) (photo- and electrochemical activity). Here, we report on the synthesis, characterization, and liquid-crystalline properties of four optically active fullerodendrimers, which are chiral at the point of conjunction between the fullerene scaffold and the mesogenic moieties. Thus, the novelty of this study is to take advantage of the asymmetric carbon atom created during the 1,3-dipolar cycloaddition reaction on C(60) in order to induce mesoscopic chirality in the materials. Four diastereoisomeric fulleropyrrolidines ((R,S)-1, (R,R)-1, (S,R)-1, and (S,S)-1) were synthesized and associated with a second-generation nematic (N) dendron to give fullerodendrimers ((R,S)-2, (R,R)-2, (S,R)-2, and (S,S)-2) which display chiral nematic (N*) phases. The absolute configurations of the stereogenic centers were determined by X-ray crystallography, 1D and 2D NMR experiments, and circular dichroism (CD) spectroscopy. The liquid-crystalline properties of the fullerodendrimers were studied by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The fulleropyrrolidine derivatives 2 exhibit supramolecular helicoidal organizations with a right-handed helix for the (R,S)-2 and (R,R)-2 diastereoisomers and a left-handed helix for the (S,R)-2 and (S,S)-2 diastereoisomers. This result suggests that the self-organization of such supermolecular materials can be controlled at the molecular level by the introduction of only one chiral center.

Usefulness of intra-abdominal pressure in a predominantly medical intensive care unit.

BACKGROUND: The deleterious effects of elevated intra-abdominal pressure (IAP) have been known for more than a century. The proposed objectives were to measure changes in IAP and analyze increase-related factors and complications and whether high IAP and its persistence are related to complications and mortality in a predominantly medical intensive care unit. METHODS: Over a 1-year period, we conducted a prospective cohort study in which IAP was measured using the bladder method. Hospitalization time, demographic variables, diagnosis on admission, APACHE II score, and clinical complications were recorded. RESULTS: A total of 130 patients were studied. Overall mean IAP was 12.3 mm Hg (standard deviation [SD], 3.79; 95% confidence interval [CI], 11.7-13), and on the first day, 12.68 mm Hg (SD, 5.32; 95% CI, 11.8-13.6); maximum IAP was 16.4 mm Hg (SD, 4.6; 95% CI, 15.6-17.2). A positive correlation was found between IAP, APACHE (Acute Physiology And Chronic Health Evaluation) II, and age. Higher IAP values were independently associated with higher age, prolonged activated partial thromboplastin time, need for dialysis, and intolerance to enteral feeding. The value showing the best sensitivity and specificity in predicting mortality was persistence of IAP 20 mm Hg or greater for 4 days or more. The number of days with IAP 20 mm Hg or greater was a factor associated with a higher risk of death (odds ratio, 2.3). Patients who died showed a tendency to increased IAP. CONCLUSION: In this study, a threshold IAP of 20 mm Hg and its permanence over time were the best predictive factors of complications and mortality. Among other relationships, we also observed that older patients had higher IAP. High IAP was a cause of intolerance to enteral nutrition.

Transmission and amplification of information and properties in nanostructured liquid crystals.

In recent years the design of chemical structures of liquid-crystalline materials has developed rapidly, and in many cases changed radically. Since Reinitzer's days, liquid crystals have either been classed as rodlike or disclike, with combinations of the two leading to phasmidic liquid crystals. The discovery that materials with bent molecular structures exhibited whole new families of mesophases inspired investigations into the liquid-crystal properties of materials with widely varying molecular topologies-from pyramids to crosses to dendritic molecules. As a result of conformational change, supermolecular materials can have deformable molecular structures, which can stabilize mesophase formation, and some materials that are non-mesogenic, on complexation form supramolecular liquid crystals. The formation of mesophases by individual molecular systems is a process of self-organization, whereas the mesophases of supramolecular systems are formed by self-assembly and self-organization. Herein we show 1) deformable molecular shapes and topologies of supermolecular and self-assembled supramolecular systems; 2) surface recognition processes of superstructures; and 3) that the transmission of those structures and their amplification can lead to unusual mesomorphic behavior where conventional continuum theory is not suitable for their description.

Grafting liquid crystalline polymers from cellulose substrates using atom transfer radical polymerization.

Immobilizing liquid crystalline polymers on cellulose generates new possibilities of accomplishing addressable/responsive bio-based substrates. In this paper we report on our first steps to combine the electro-optic properties of liquid crystals with the versatility of paper as a displaying substrate. Electric current or magnetic fields can be used to manipulate the orientation of liquid crystals and thereby change the appearance and the properties of the material. Atom transfer radical polymerization (ATRP) can be used successfully to graft polymers from solid substrates in a controlled manner. In this study it is shown that the grafting of a liquid crystalline monomer, 11-(4'-cyanophenyl-4″-phenoxy)undecyl acrylate, onto cellulose by ATRP is possible, and that thicker films can be obtained by using PMA as a spacer in between the cellulose and the liquid crystalline block. The cellulose fibers become highly hydrophobic subsequent to grafting and the liquid crystalline polymer possesses mesophases accessible for further processing.

An optically-active liquid-crystalline hexa-adduct of [60]fullerene which displays supramolecular helical organization.

Polyaddition of mesogenic moieties to C60 were found to yield chiral supermolecular nanoparticles which exhibit iridescent helical chiral nematic phases.

"Janus" supermolecular liquid crystals--giant molecules with hemispherical architectures.

Liquid crystals represent a unique class of self-organising systems, which although found in many day-to-day practical material applications, such as displays, are also intimately entwined with living processes. They have the potential, just like living systems, to provide us with a unique vehicle for the development of self-ordering nano- and mesoscopic-engineered materials with specific functional properties. In this article we describe a new concept for the design of self-assembling functional liquid crystals as segmented or "Janus" liquid-crystalline supermolecular materials in the form of structures that contain two different types of mesogenic units, which favour different types of mesophase structure, grafted onto the same star-shaped scaffold to create supermolecules that contain different hemispheres. The materials exhibit chiral nematic and chiral smectic C phases.