J. Brossas

Action of elementary sulfur onto carbanions : a new route to dialkylpolysulfides

Abstract The reaction of sec-Butyllithium with elemental sulfur leads to the formation of dialkylpolysulfides.

Investigation of some intrinsic parameters influencing the flammability of ω or α, ωphosphonated polystyrenes (III)

SummaryThis paper concerns the study of some chemical intrinsic parameters governing the fire retardant properties of polystyrenes carrying phosphorus atoms at one or both ends of their macromolecular chain. It is shown that their low flammability, depends on the presence of labile atoms, bonded, either directly to the phosphorus atom or in the α position to the phosphorus atom.

Thermal decomposition of 4,4′-azobis(4-cyanopentanol)

SummarySeveral workers (Reed, 1971, 1972, Goldfein, 1975, Kartavykh, 1977) have employed the 4.4′-azobis(4-cyanopentanol) (ACP) as the initiator for the radical polymerization of butadiene, isoprene or acrylic monomers. Nevertheless, the decomposition of (ACP) has never been studied, only the rate constant of decomposition (kd) of (ACP) at 70 °C in acetone has been determined.The present paper reports the kinetics of the thermal decomposition of (ACP): the rate constant of decomposition (kd) at various temperatures and the activation energy of decomposition are determined in dimethyl sulfoxide.

Structure flammability relationships of phosphorus containing polystyrene samples (I)

SummaryPhosphonated polystyrene flammability is discussed in relation to their structure. It is shown that the oxygen Index of phosphonated polystyrenes depends mainly on the position of the phosphorus atoms on the backbone of the polymer and not on the absolute phosphorus content.

NMR study of the complexation of secondary-butyllithium by N,N,N′,N′-tetramethylethylenediamine

Abstract Complexation of secondary-butyllithium (sec-BuLi) by N,N,N′,N′ -tetramethylethylenediamine (TMEDA) has been examined by NMR spectroscopy at various temperatures. The upfield chemical shift of the α-methine proton of the sec-BuLi has been determined as a function of the ratio R = TMEDA/sec-BuLi. The reversible variation of the chemical shift from −50°C to −20°C is explained in terms of an endothermic disproportionation of the 1 : 1 complex (1 sec-BuLi : 1 TMEDA) to the 1 : 2 complex (1 sec-BuLi : 2 TMEDA).

Radical copolymerization of 2-hydroxyethylacrylate with alkylacrylate: Determination of the reactivity ratios

SummaryThe copolymerization of hydroxyethylacrylate with methyl-ethyl and butyl-acrylate was studied at 60°C using azo-bis-isobutyronitrile as the initiator. The monomer reactivity ratios were determined by the Fineman method. The results show that the methylacrylate-hydroxyethylacrylate monomers copolymerize in a completely random manner (Bernouillian behaviour). For the other monomer pairs, an increase in the chain length of the alkyl ester group favours the addition of hydroxyethylacrylate monomer to the alkylacrylate polymer radicals.

Synthesis of Statistical Polydiene Networks by Reaction of Liquid Polyenes with Telechelic Siloxanes

The present investigation concerns the synthesis of statistical networks similar to vulcanized rubber. We have used liquid precursor polymers: polybutadiene (PB) and polyisoprene (PI) with telechelic siloxanes. The reactivity of the polydienes can be classified as follows: PB units 1,2 ⋙ PI units 3,4 ⋙ PI units 1,4 ≃ 0. The network formation is a function of the ratio R = nb, of pendent double bonds/nb. of ≃ SiH. For R ≃ 1 the networks are rather hard and brittle, for 8 ⩽ R ⩽ 10 they are soft and elastic, whereas for R ≃ 16 the gels obtained are very soft and sticky.

2. Synthesis of statistical networks from liquid telechelic dimethylhydrogenosilane polydiene

A new route to the synthesis of statistical networks similar to vulcanized rubber, from 1,2-polybutadiene (PBD) and 3,4-polyisoprene (PI) is described. The two antagonist chemical functions are both present on the polydiene backbone. The latter could be used as precursor polymer and as difunctional crosslinker simultaneously; the reactive groups are respectively the dimethylhydrogenosilane end groups and the pendent double bonds along the polydiene backbone.

Synthesis of Polyphenylene Polysulfur

SummaryPolymers with conjugated double bonds are both of theoretical and practical interest. Poly (thio-1, 4 phenylene), which is called poly (phenylene sulfide) (or PPS), is an original class of polymers capable of displaying conductive properties. Usually, PPS are prepared by Friedel-Crafts reaction or by Macallum synthesis. In this paper we describe another way to obtain poly (phenylene polysulfane). They are prepared in a one-pot reaction with alcali metal, S8 and p-dichlorobenzene. The reaction is studied on model molecules.

Effect of free radicals generating compounds towards the flammability of w-phosphonated polystyrenes — V

SummaryEffect of some free-radicals generating compounds, such as organic peroxides, hydroperoxides and polysulfides, on the Oxygen Index of end phosphonated polystyrenes is investigated. It is shown that some combinations of end phosphonated polystyrene with free-radicals initiators, may be said to have a synergestic effect on flame-retardant properties of standard polystyrene.