Polymer blends based on the β-modification of polypropylene

iPP/sPP, iPP/rPP, iPP/PVDF and iPP/PA-6 blends, and their β-nucleated forms were prepared in the present study. The components of iPP/sPP and iPP/rPP blends are compatible in the molten state. The phase structure of the melt of iPP/PVDF and iPP/PA-6 blends is heterogeneous. The melting and crystallisation characteristics as well as the structure and polymorphic composition of these blends were studied by polarised light microscopy (PLM) and differential scanning calorimetry (DSC). When semicrystalline polymers are added to iPP, the most important factor of the formation a blend with β-crystalline phase is the α-nucleation effect of the second polymer. In the case of polymers with an α-nucleating effect, the temperature range of their crystallisation should be lower than that of β-iPP. β-nucleated iPP/PVDF and iPP/PA-6 blends are extreme examples showing that completely β-iPP matrix can not form even in the presence of a highly effective β-nucleant, because of the strong α-nucleating ability and higher crystallisation temperature range of PVDF and PA-6. We found that the β-crystallisation tendency of random propylene copolymers can be enhanced by adding an iPP homopolymer.     

Impact of High-Pressure Homogenization on the Cell Integrity of Tetradesmus obliquus and Seed Germination

Microalgae have almost unlimited applications due to their versatility and robustness to grow in different environmental conditions, their biodiversity and variety of valuable bioactive compounds. Wastewater can be used as a low-cost and readily available medium for microalgae, while the latter removes the pollutants to produce clean water. Nevertheless, since the most valuable metabolites are mainly located inside the microalga cell, their release implies rupturing the cell wall. In this study, Tetradesmus obliquus grown in 5% piggery effluent was disrupted using high-pressure homogenization (HPH). Effects of HPH pressure (100, 300, and 600 bar) and cycles (1, 2 and 3) were tested on the membrane integrity and evaluated using flow cytometry and microscopy. In addition, wheat seed germination trials were carried out using the biomass at different conditions. Increased HPH pressure or number of cycles led to more cell disruption (75% at 600 bar and 3 cycles). However, the highest increase in wheat germination and growth (40–45%) was observed at the lowest pressure (100 bar), where only 46% of the microalga cells were permeabilised, but not disrupted. Non-treated T. obliquus cultures also revealed an enhancing effect on root and shoot length (up to 40%). The filtrate of the initial culture also promoted shoot development compared to water (21%), reinforcing the full use of all the process fractions. Thus, piggery wastewater can be used to produce microalgae biomass, and mild HPH conditions can promote cell permeabilization to release sufficient amounts of bioactive compounds with the ability to enhance plant germination and growth, converting an economic and environmental concern into environmentally sustainable applications.     

Thermal and optical studies on hexa-2,4-diyne-1,6-diyl-bis(4-n-hexoxybenzoate)

As part of a programme investigating mesogenic diacetylenes a symmetrically disubstituted diacetylene has been synthesized and polymerized. Thermal, thermo-optical and IR studies have been carried out to investigate the different crystalline forms of the diacetylene.     

The rearrangement of phosphitohydrazide ligand [(ArO)2P-NPh-NPh-] into iminophosphoranate anion [(PhNP(OAr)2-NPh-] {(ArO)2P = [CH2(BuMeC6H2O)2P]} in coordination sphere of divalent cobalt

The reaction of bromophosphite (ArO)₂PBr {(ArO)₂P = CH₂(6-^tBu-4-Me-C₆H₂O)₂P} with lithium salt of 1,2-diphenylhydrazine gave phosphitohydrazine (ArO)₂P-NPh-NPhH (2) in 64% yield. The last one reacted with Co[N(SiMe₃)₂]₂ to afford cobalt(II) iminophosphoranate (PhNP(OAr)₂-NPh-)₂Co (3), which is the result of isomerisation of the phosphitohydrazide ligand in coordination sphere of divalent cobalt.     

Structure and rheological behavior of casein micelle suspensions during ultrafiltration process

The stability and mechanism underlying the formation of deposits of casein micelles during ultrafiltration process were investigated by small-angle and ultra small-angle x-ray scattering (SAXS and USAXS). The casein micelle dispersions consisted of phospho-caseinate model powders and the measurements probed length scales ranging from 1 to 2000 nm. Rheometric and frontal filtration measurements were combined with SAXS to establish the relationship between the rheological behavior of deposits (shear and/or compression) and the corresponding microstructure. The results revealed two characteristic length scales for the equilibrium structure with radius of gyrations R(g), about 100 and 5.6 nm pertaining to the globular micelles and their non-globular internal structure, respectively. The SAXS measurements further indicated that the increase of temperature from 20 to 70 degrees C or the decrease of pH from 6.6 to 6 lead to agglomeration of the globular micelles. In situ scattering measurements showed that the decrease of permeation flows is directly related to the deformation and compression of the micelles in the immediate vicinity of the membrane.     

Structure and orientation dynamics of sepiolite fibers–poly(ethylene oxide) aqueous suspensions under extensional and shear flow,probed by in situ SAXS

The structure and orientation dynamics of sepiolite clay fibers about 1,000 nm long and 10 nm thick, suspended in an aqueous poly(ehtylene oxide) matrix of 10⁵ g/mol molecular mass, have been studied under control extensional and shear flow. A new extensional flow cell developed at the “Laboratoire de Rhéologie” and the combined rheology and small angle X-ray scattering (Rheo-SAXS) setup available at the European Synchrotron Radiation Facility have allowed access to in situ and time-resolved fiber orientations and structure properties in the volume of suspensions under flow. In the volume fractions and shear rate domains for which the suspensions exhibit shear-thinning properties, two regimes of orientation separated by a critical strain rate have been identified under extensional flow.     

Preparation and investigations of polyimides III

Polyamide acid powders of pyromellitic dianhydride and 4,4-diaminodiphenyl ether base were prepared in tetrahydrofuran, in the heterogeneous phase. The imidization of these powders was investigated by thermogravimetric, calorimetric and mass-spectrometric methods.According to the TG and DSC data, the temperatures of the beginning and maximum rate of imidization increase with increasing temperature and duration of imidization.A linear relationship has been found to exist between the weight loss and the reaction heat of the imidization process. The reaction heat corresponding to unit weight loss increases with decreasing molecular weight.Dicarboxylic anhydrides, applied as chain-terminators, do not affect the thermal properties of polyamide acids to an appreciable extent.Imidization has been found to be a complex process, in which decomposition of polyamide acids also takes place besides dehydrocyclization. The kinetics of imidization are satisfactorily described by a first-order dehydrocyclization and a parallel first-order decomposition. The weight loss during imidization is higher than the loss calculated on the basis of dehydrocyclization, which must be due to the release of the decomposition products of the polyamide acid, the release of solvated or complexed tetrahydrofuran, or that of possible oligomeric clusters.

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Zusammenfassung Polyamidsäurepulver von Pyromellitdianhydrid und 4,4-Diamino-diphenyläther wurden in Tetrahydrofuran in heterogener Phase hergestellt. Die Imidisierung dieser Pulver wurde durch thermogravimetrische, kalorimetrische und Massenspektrometrische Methoden verfolgt.Nach TG- und DSC-Angaben steigt die Temperatur des Beginns und der Maximalgeschwindigkeit der Imidisierung mit steigender Temperatur und Imidisierungsdauer an.Ein linearer Zusammenhang wurde zwischen Gewichtsverlust und Reaktionswärme des Imidisierungsvorgangs gefunden. Die der Einheit des Gewichtsverlustes entsprechende Reaktionswärme nimmt mit abnehmendem Molekulargewicht zu.Als Kettenende angewandte Dicarboxylanhydride beeinflussen die thermischen Eigenschaften der Polyamidsäuren nicht in merklichem Maße.Es wurde festgestellt, daß die Imidisierung ein komplexer Vorgang ist, in dem außer der Dehydrocyclisierung auch eine Zersetzung der Polyamidsäuren stattfindet. Die Kinetik der Imidisierung kann durch eine Dehydrocyclisierung erster Ordnung und eine parallele Zersetzungsreaktion erster Ordnung befriedigend beschrieben werden. Der Gewichtsverlust während der Imidisierung ist höher als der aufgrund der Dehydrocyclisierung berechnete Verlust, was der Abspaltung von Zersetzungsprodukten der Polyamidsäure, der Freisetzung von solvatiertem oder komplexgebundenem Tetrahydrofuran oder eventueller oligomerer Einschlüsse zuzuschreiben ist.

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Résumé Les polyamides en poudre résultant du dianhydride pyromellitique et de l'éther 4,4-diaminodiphénylique ont été préparés en phase hétérogène dans le té trahydrofuranne. La formation d'imides à partir de ces poudres a été étudiée par thermogravimétrie, calorimétrie et spectrométrie de masse.D'après les résultats obtenus par TG et DSC, les températures du début de la formation d'imide et la vitesse maximale de la réaction augmentent avec l'accroissement de la température et de la durée de la réaction.On a trouvé une corrélation linéaire entre la perte de poids et la chaleur de formation de l'imide. La chaleur de réaction correspondant à l'unité de perte de poids augmente quand le poids moléculaire diminue.Les anhydrides dicarboxyliques utilisés en bouts de chaines n'ont pas d'effet appréciable sur les propriétés thermiques des polyamides.On a établi que la formation d'imide est un processus complexe, au cours duquel, outre la déshydrocyclomérisation, une décomposition des polyamides a également lieu. La cinétique de la réaction peut être décrite de façon satisfaisante par une déshydrocyclomérisation du premier ordre et une réaction de décomposition parallèle également du premier ordre. Lors de la formation d'imide la perte de poids est plus élevée que celle calculée à partir de la déshydrocyclomé risation, ce qui provient sans doute du dégagement des produits de décomposition du polyamide, du dégagement du tétrahydrofuranne solvaté ou complexé ou bien de celui des inclusions oligomères éventuelles.

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Migratory insertion of the R2P group into a nitrogen-nitrogen bond - a novel type of rearrangement in phosphorus-nitrogen ligand chemistry. 3. The rearrangement of triphosphinohydrazide ligand -N(PPh2)-N(PPh2)2 to triphosphazenide anion {[(Ph2P-N]2PPh2}- in the coordination sphere of divalent cobalt and nickel

Hydrazine dihydrochloride reacts with 3 equiv of Ph2PCl in tetrahydrofuran in the presence of triethylamine to give tris(diphenylphosphino)hydrazine (1) in 70% yield. Each nitrogen atom in 1 has a trigonal-planar environment according to X-ray analysis. Thermolysis of 1 at 130 degrees C results in the formation of two products: bis(diphenylphosphino)amine and octaphenylcyclotetraphosphazene. The interaction of free ligand 1 with NiBr2 affords a simple adduct [(Ph2P)2N-NH-PPh2]NiBr2, while its anionic (hydrazide) form undergoes rearrangement in a coordination sphere of divalent cobalt and nickel involving migratory insertion of the Ph2P group into a nitrogen-nitrogen bond. The reaction of 1 with cobalt bis(trimethylsilyl)amide, [(Me3Si)2N]2Co, yields the complex of phosphazenide-type (Me3Si)2N-Co[(Ph2PN)2PPh2] (2) in 86% yield. A similar reaction of 1 with nikelocene proceeds with substitution of one Cp ring to form durable 18-electron complex CpNi[(Ph2PN)2PPh2] (3).     

Preparation and Characterization of Pentafluoro-λ6-sulfanyldifluoromethane and Pentafluoro-λ6-sulfanyl-1,1,2,2-tetrafluoroethane

The pentafluorosulfanyl-λ⁶-perfluoroalkyl halides SF₅CF₂I, SF₅CF₂CF₂Br, and SF₅CF₂CF₂I were prepared for use in the syntheses of other SF₅-containing compounds. For example, new, convenient syntheses were developed for the hydro compounds SF₅CF₂H and SF₅CF₂CF₂H from the reduction of these iodides or bromides with either triethylborane or tributyltin hydride. Herein, more thorough spectroscopic analyses of the hydro compounds are presented, including multinuclear NMR and vibrational spectroscopy, mass spectrometry, and computational chemistry. Unfortunately, under the conditions tried, little to no evidence was obtained for potential SF₅(CF₂)_n- (where n=1 or 2) transfer reagents such as SF₅(CF₂)_nSi(CH₃)₃ or Cu(CF₂)_nSF₅.