Synthesis of π-conjugated thiophenes starting from substituted 3-oxopropanenitriles via Gewald reaction

This paper describes the synthesis of β-aryl and β-heteroaryl substituted 2-aminothiophenes as a novel class of building blocks in oligo- and polythiophenes. The synthesis was carried out in two steps, involving synthesis of substituted 3-oxopropanenitrile intermediates, followed by the Gewald reaction.     

Quantitative Characterization of the Structure of PP/Layered Silicate Nanocomposites at Various Length Scales

The structure and rheological properties of a large number of layered silicate polypropylene nanocomposites were studied with widely varying compositions. Unlike general practice, morphology was characterized at different length scales covering several decades by SEM, TEM, and XRD. Rheological measurements supplied additional information about structure. The results showed that these materials possess a very complex structural architecture. The introduction of a functionalized polymer decreases the size of the original clay particles. However, relatively large silicate particles were found also in composite samples yielding XRD traces without silicate reflection. We found that not only two (individual layers, intercalated stacks), but four morphological entities, i.e. also particles and a silicate network, may be present simultaneously in the composites. An attempt was made to characterize morphology quantitatively, wherever possible. SEM and TEM micrographs were evaluated by image analysis, XRD traces by curve fitting, while a model was developed to determine relaxation time from rheological measurements, but only XRD and SEM results are reported here.     

Synthesis of novel 1‐substituted [1,3]thiazolo[3,2‐a]‐[1,5]benzodiazepine derivatives from 1,5‐benzodiazepine‐2‐thiones and α‐halogen carbonyl compounds

A number of substituted 4H,5H,6H‐thiazolo[3,2‐a][1,5]benzodiazepinium salts 2a‐h, 5, 9 , which are based on the novel thiazolobenzodiazepine system, were prepared by condensation‐cyclization of 1,5‐benzodiazepine‐2‐thiones 1a‐f, h, 4 with α‐haloketones, as well as with α‐bromoacetaldehyde diethyl acetal. The structure and stereochemistry of the ring system obtained were investigated by ¹H and ¹³C nmr spectroscopy: the additional heterocyclic nucleus was found to appreciably influence the conformational mobility of the heptatomic ring. Upon treatment of salt 2d with alkali the presence of the base enamine structure in solution has been postulated.     

Synthesis of Bis(phosphinoyl)amines and Phosphinoyl–Phosphorylamines by the N‐Phosphinoylation and N‐Phosphorylation of 1‐Alkylamino‐2,5‐dihydro‐1H‐phosphole 1‐Oxides

The N‐phosphinoylation and N‐phosphorylation reaction of 1‐alkylamino‐2,5‐dihydro‐1H‐phosphole 1‐oxides with diphenylphosphinoyl chloride and diethylphosphoryl chloride/diphenylphosphoryl chloride afforded new families of compounds comprising bis(phosphinoyl)amines and phosphinoyl‐phosphorylamines, respectively, whose stereostructures were elucidated by B3LYP/6‐31G(d,p) and B3LYP/6‐31G++(d,p) calculations. The P analogues of the mixed imides may be valuable intermediates in syntheses.     

Thermo-oxidative stability of polypropylene/layered silicate nanocomposites

Several series of experiments were carried out to check the effect of components on the stability of PP/layered silicate nanocomposites. The amount of organophilic montmorillonite (OMMT) changed between 0 and 6, while that of maleated polypropylene (MAPP) between 0 and 50 vol%. The composites were prepared in an internal mixer at 190 °C. Mixing speed and time were changed to study the effect of processing conditions on stability. The structure of the samples was characterised by various methods, while stability by the induction time of oxidation (OIT), the onset temperature of degradation (OOT) and by colour. Contrary to numerous claims published in the literature, which indicate the positive effect of layered silicates on the stability of polymer nanocomposites, our results clearly proved that both OMMT and MAPP accelerate degradation during processing and deteriorate the properties of PP composites. Residual stability decreases drastically with increasing amounts of both components, chain scission leads to the decrease of viscosity and to inferior strength and deformability. In spite of expectations, the effect of the components is independent of each other. Discoloration is caused mainly by the inherent colour of the filler and it decreases with increasing exfoliation. The most probable reason for decreased stability is the reaction of the components with the stabilisers, but this explanation needs further verification. Processing conditions influence degradation considerably, increasing shear rate and longer residence times lead to more pronounced degradation. The basic stabilization of commercial grade polypropylenes is insufficient to protect the polymer against degradation and without additional stabilization processing under normal conditions results in products with inferior quality.     

Network Formation in PP/Layered Silicate Nanocomposites: Modeling and Analysis of Rheological Properties

PP/organophilic montmorillonite composites were prepared from PP homopolymer, maleinated polypropylene and a clay organophilized with octadecyl amine. Various approaches were used to analyze the rheological properties of the composites. Cole-Cole plots proved to be useful, since they detect the network very sensitively. The frequency dependence of the real part of complex viscosity was described with a series of Maxwel bodies coupled parallel to each other. The relaxation time of the melt changed in the range of 0.0005 and 200 sec. Under certain conditions long relaxation times appear in the spectrum, which indicate the formation of new structural units, probably a silicate network. A certain number of silicate layers are needed to create a house-of-cards structure. A threshold concentration of MAPP exists for network formation, which depends on silicate content.