Observations on the Modified Wenker Synthesis of Aziridines and the Development of a Biphasic System

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Organic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jo302615gA cheap and reliable process for the modified Wenker cyclization to afford aziridines has been achieved using biphasic conditions for a range of amino alcohol starting materials. A 100 mmol “one-pot” process has also been devised and enantiopurity of the starting amino alcohol is retained in the aziridine product

Preparation of Thermostable Rigid Foams by Control of the Reverse Diels—Alder Reaction During the Cross-Linking of Bis-nadimide Oligomers

International audienceA new chemical approach using the polymerization of nadimide end-capped oligobenzhycholimide (BBN) was found to produce rigid thermostable foams. Two BBNs with a theoretical molecular weight of 1000 and 1500 D were prepared. Under thermal curing (up to 300 °C), cyclopentadiene evolution takes place through a reverse Diels-Alder reaction during the gelation of the systeme (cross over of storage and loss moduli). To obtain good mechanical properties, BBNs were blended with 3% of linear thermostable polymers. Foams with density ranging between 50 to 400 kg/m3 (3 to 25 lb/ft3) were prepared. These materials exhibit low moisture uptake (2.5%) and an onset of decomposition at about 350 °C. Other interesting features of these materials are their insulating properties, non flammable character and good compressive strength up to 300 °C

Thermal polymerization of arylacetylenes: 1. Study of a monofunctional model compound

International audienceThe thermal polymerization of arylacetylene compounds has been studied from a monofunctional model compound, 4-(hexyloxy)phenylacetylene I. I was synthesized and bulk polymerized under several experimental conditions. The reaction products were analysed by chromatography, spectroscopy and spectrometry techniques. The observed average polymerization degree is low. The lowest molecular weight compounds were isolated and identified: they are two naphthalenic dimers and three benzenic trimers. They represent 30 wt% of the whole polymerization product. We have shown also that the thermal polymerization of I is temperature and time dependent and that a depolymerization process takes place at high temperatur

Structure/properties relationship of nadimide-terminated fluorinated polyimides. Part II. New thermostable systems

cited By 5International audienceWe have established the chemical structure/mechanical properties relationships of new nadimide-terminated polyimides. Initially, the prepolymers were synthesized by polycondensation of nadic anhydride (NA), hexafluoroisopropylidene-2,2-bis(phthalic acid anhydride) (6HFDA) and two phenylene diamines, meta (mPDA) and para (pPDA) in N-methylpyrrolidone (NMP). After characterizing the microstructure and composition of these systems using Chromatographic (HPLC, SEC) and spectroscopic techniques (1H and 13C NMR), we determined their thermomechanical properties. The rheology curves obtained showed the presence of two transitions, α and β, associated with the glass transition and a second, sub-vitreous transition, because of local molecular movements. By studying the relationship between chemical structures and mechanical properties, we have shown the influence of endo/exo isomerization of nadimide extremities on the glass transition temperature Tg. In a given polymer, the value of Tg increases with increasing percentage of exo isomers