Association behavior of binary polymer mixtures under elongational flow

The influence of elongational flow on the association behavior of binary mixtures of functionalized polymers capable of forming single reversible orientationally dependent bonds, such as hydrogen bonds, is studied analytically. Applying a mean-field approach with an external potential representing the effect of the elongational flow, the orientation distribution functions for the dumbbell model and the freely jointed model of a polymer chain were obtained. Two opposite factors determine the association of “linear” diblock copolymerlike chains: the unfavorable extra stretching under flow of associated polymer chains and the favorable orientation of the chains (segments) along the flow direction. The former dominates and the fraction of associated “linear” chains decreases with increasing flow rate. For mixtures of polymers which are capable of forming associated T-chains, the association also decreases, however, more slowly, and this time due to unfavorable orientational effects. If the formation of associated linear and T-polymers as well as complex linear/T-polymers is possible, a strong preference for the formation of associated T-chains is found. At high flow rates any type of association becomes unfavorable

Random Copolymer Effect in Self-Assembled Hydrogen-Bonded P(S-co-4VP)(PDP) Side-Chain Polymers

Random copolymers of styrene and 4-vinylpyridine P(S(1-x)-co-4VP(x)) were synthesized to study the effect of the random copolymer "repulsion" on the self-assembly in hydrogen-bonded complexes with pentadecylphenol (one PDP molecule per 4VP group). The major trends observed as a function of the fraction of styrene monomers 1 - x in the random copolymer are a decrease in order-disorder transition temperature, T(ODT), and a decrease in the periodic length scale of the ordered lamellar state. The lower T(ODT) results from a partial shielding in the disordered state of the highly unfavorable styrene/4-vinylpyridine interactions by the PDP alkyl tails. The reduced layer thickness in the ordered state is due to the relaxation into a more coil-like conformation of the alkyl tails of the PDP amphiphiles, made possible by the presence of styrene units. The self-assembly properties of P(S(1-x)-co-4VP(x))(PDP)(1.0) are compared with those of the lamellar self-assembled homopolymer-based P4VP(PDP)(x) system, where x denotes the number of PDP molecules per 4VP repeat unit. As in P(S(1-x)-co-4VP(x))(PDP)(1.0), in P4VP(PDP)(x) also only a fraction x of the total number of monomers of the macromolecule may potentially hydrogen bond with PDP molecules at any given instant. In contrast to P(S(1-x)-co-4VP(x))(PDP)(1.0), for P4VP(PDP),, however, the long period is found to increase for decreasing values of x

Annealing-Induced Changes in Double-Brush Langmuir-Blodgett Films of α-Helical Diblock Copolypeptides

The effect of annealing on the structure and the helix orientation in Langmuir-Blodgett (LB) monolayers of diblock copolymers (PLGA-b-PMLGSLGs) of poly(α-L-glutamic acid) (PLGA) and poly(γ-methyl-L-glutamate-ran-γ-stearyl-L-glutamate) with 30 mol % of stearyl substituents (PMLGSLG) with unidirectional helix orientation deposited on hydrophilic silicon substrates was characterized by means of small-angle X-ray reflectivity, transmission Fourier transform infrared spectroscopy, and atomic force microscopy. Upon annealing at 100 °C for 24 h, the α-helices became less tilted toward the substrate surface normal. Surface area shrinkage accompanied the change in tilt, indicated by an increase in both film thickness and electron density, resulting in more compact and uniform films. The enhancement of the helix orientation by thermal annealing was greater for the PMLGSLG block and for the diblock copolymers with the shorter block lengths. For these diblock copolymers, annealing resulted in postorientation of the PMLGSLG block helices almost perpendicular to the substrate surface. This effect originates from a considerable increase in intermolecular packing of the PLGA block caused by hydrogen bonds between the carboxylic groups upon annealing, as well as the high mobility of the PMLGSLG block helices for rearrangement favored by the melted side chain mantle at elevated temperatures.

4-(4-Ethyl­phenyl­diazen­yl)phenol

The crystal structure of the title compound, C14H14N2O, determined at 100 K, shows that the mol­ecules are not planar in the solid state, in contrast to other diazene (azobenzene) derivatives. The dihedral angle between the planes of the two aromatic rings is 42.32 (7)°. The mol­ecules are linked by inter­molecular O—H⋯N hydrogen bonds, forming an infinite one-dimensional chain

Alpine altitude climate treatment for severe and uncontrolled asthma: an EAACI position paper

Currently available European Alpine Altitude Climate Treatment (AACT) programs combine the physical characteristics of altitude with the avoidance of environmental triggers in the alpine climate and a personalized multidisciplinary pulmonary rehabilitation approach. The reduced barometric pressure, oxygen pressure, and air density, the relatively low temperature and humidity, and the increased UV radiation at moderate altitude induce several physiological and immunological adaptation responses. The environmental characteristics of the alpine climate include reduced aeroallergens such as house dust mites (HDM), pollen, fungi, and less air pollution. These combined factors seem to have immunomodulatory effects controlling pathogenic inflammatory responses and favoring less neuro-immune stress in patients with different asthma phenotypes. The extensive multidisciplinary treatment program may further contribute to the observed clinical improvement by AACT in asthma control and quality of life, fewer exacerbations and hospitalizations, reduced need for oral corticosteroids (OCS), improved lung function, decreased airway hyperresponsiveness (AHR), improved exercise tolerance, and improved sinonasal outcomes. Based on observational studies and expert opinion, AACT represents a valuable therapy for those patients irrespective of their asthma phenotype, who cannot achieve optimal control of their complex condition despite all the advances in medical science and treatment according to guidelines, and therefore run the risk of falling into a downward spiral of loss of physical and mental health. In the light of the observed rapid decrease in inflammation and immunomodulatory effects, AACT can be considered as a natural treatment that targets biological pathways