Télomérisation de l'isobutylène

The telomerization of isobutene was investigated using redox catalysis, free radical, and particularly cationic initiation. The influence of the initiator on the degree of polymerization and the structure of the telomers was studied. Redox and free radical telomerization with CCl₄ and CCl₃Br were found to permit synthesis and identification of the monoadduct structure. Cationic telomerization gives regular structure compounds and the molecular weights are higher than those obtained by other methods of telomerization.     

Synthèse de cotélomères photoréticulables, 6. Utilisation de cotélomères biséquencés

Photocrosslinkable block cotelomers were synthesized in three steps. In the first step a monomer M₁ was telomerized with carbon tetrachloride or chloroform, in the second step a monomer M₂ with the resulting macrotelogen, and in the third step the hydroxyl groups were esterified by cinnamic acid or acrylic acid. These reactions were carried out with ethyl acrylate (M₁)/CCl₄ by redox catalysis and subsequently with vinyl acetate (M₂) by free radical initiation, or with vinyl acetate (M₁)/CHCl₃ by free radical initiation and subsequently with isoprene (M₂) by redox catalysis, or with 2-hydroxyethyl acrylate (M₁)/CCl₄ by redox catalysis, and subsequently with isoprene (M₂) by redox catalysis.     

Etude de la diaddition de l'acétate d'allyle sur les télogènes chlorofluorés possédant deux groupements CCl3 en extrémité de chaîne

The redox catalyzed addition of compounds such as Cl₃C? CF₂? CCl₃ and Cl₃C? CF₂? CCl₂? CH₂? CHCl? CH₂? OCOCH₃ to allyl acetate was studied with the purpose of obtaining telechelic products. RuCl₂[P(C₆H₅)₃]₃ was used as catalyst, and its action was compared to that of cooper- or iron-based catalysts. The products were isolated and their structures studied by means of ¹³C, ¹⁹F and ¹H NMR spectroscopy. The reaction mechanism was studied to improve the yield of the diaddition product for its utilisation as monomer in polycondensation reactions. It was found that the low reactivity for a second addition is not due to the presence of a chlorine atom in β-position of the acetate function. When allyl acetate was replaced by allyl bromide or chloride in the first addition, the second addition to allyl acetate occurred normally.     

Synthèse de composées photoréticulables, 7. Télomères des acides acrylique et méthacrylique gréffés par méthacrylate d'époxy-2,3 propyle

Telomers were prepared from acrylic or methacrylic acid and CCl₃Br, C₁₂H₂₅SH, C₁₈H₃₇SH or C₈F₁₇C₂H₄SH by initiation with 2,2'-azoisobutyronitrile. The transfer constant of CCl₃Br and the thiols, which are about 0,03 and 0,5, respectively, were determined. These telomers were used as supports of photopolymerizable functions, which were introduced by grafting of 2,3-epoxypropyl methacrylate, catalysed with dodecyldimethylamine. The reactions were followed by ¹H NMR, elemental analyses, tonometrie, and especially by GPC and titration of the acid functions. The grafting telomers, holding many acrylic functions which react upon UV and electron irradiation, give photoreticulated varnish coatings with very interesting properties.     

Télomères monofonctionnels du chlorure de vinyle, 2. Cinétique par amorçage radicalaire

Radical telomerizations of vinyl chloride with telogens R? CCl₃, containing alcohol and acid functions in the R group, were carried out. The molecular weights of the obtained products are between 1000 and 10 000. Transfer constants (C_T) were calculated for each case by studying the DP_n (10 to 50) variation as a function of the mole ratio (R) of telogen to monomer. In addition, the functionality of the resulting poly(vinyl chloride) was evaluated from the values of C_T and R.     

Etude du comportement d'une série de polystyrènes linéaires dans des mélanges de solvants

The preferential solvation of anionically polymerised polystyrene by different solvent/non solvent mixtures (CCl₄/CH₃OH, C₆H₆/CH₃OH, dioxane/CH₃OH, C₆H₆/Heptane) was studied by light scattering. The parameter λ′ of preferential solvation depends on molecular weight M according to where λ′_∞ is the preferential solvation at infinite molecular weight and A a quantity characteristic for the composition of the mixed solvent. A increases with decreasing thermodynamic goodness of the solvent mixture. The above equation can be derived semi-empirically by assuming that the solvent composition near the chain depends on the density of chain segments. This hypothesis furthermore explains the observed anomalous behavior of the intrinsic viscosity/molecular weight relationship below molecular weights of about 160,000 in solvent/non solvent mixtures.     

Préparation de polystyrène de masse éalevée à chaîcne aliphatique ou noyaux aromatiques deuteriés

Isotopically substituted styrene, (phenyl-²H₅) styrene ( 3 ), and selectively labled styrene, [alpha;, beta;-²H₂] styrene ( 6 ), were prepared by the classical two step synthesis, starting with the correspondingly labeled compounds. By anionic polymerization in an inert atmosphere labeled high molecular weight polystyrences 10 and 11 were prepared.     

Synthèse de monoalcools et de monoacides chlorofluorés par télomérisation avec des telogènes chlorofluorés

Telomerizations of chlorofluorinated telogens CF₃CCl₃ and \documentclass{article}\pagestyle{empty}\begin{document}$${\rm Cl\rlap{--} (CFCl \hbox{---} CF}_{\rm 2} {\rm \rlap{--} )}_{\rm n} {\rm CCl}_{\rm 3}$$\end{document} (1 ≤ n ≤ 4) with acrylic, allylic, and vinylic monomers were studied. With allyl alcohol and 2-hydroxyethyl acrylate the corresponding fluorinated adducts 1 and 2 were obtained directly. Vinyl and allyl acetates led to the adducts 4a , b and 5a , b , respectively, which could be transformed into the corresponding acetals and alcohols. Telomerizations of methyl acrylate and methacrylate led to the fluorinated adducts 12a and b in the presence of copper chloride as catalyst or also with iron trichloride in the case of methyl methacrylate. By intramolecular elimination the methacrylate adducts were transformed into the lactons 13 and 14 and the acrylate adducts by reduction into the alcohols 1 and 2 . The same reduction of the methacrylate adduct led to the 2,4,4-trichloro-5,5,5-trifluoro-2-methyl-1-pentanol ( 15 ). Independent on the applied catalyst the telomerization of vinylacetic acid led to the monoaddition product, whereas in the case of methacrylic or acrylic acid the formation of monoadducts or higher addition products was found to depend on the catalyst.     

Cinétiques de télomérisation, 4. Nouvelle méthode de détermination des constantes de transfert en catalyse radicalaire

For the determination of transfer constants C_T to the telogen in telomerization reactions started with free radicals we used three methods. The first one is the method of Mayo, the second one is based on the variation of the conversion degree of telogen to monomer and the last method requires the knowledge of the cumulated number-average degree of polymerization DP _n and monomer conversion α_M of the samples during the reaction. Verifications of the proposed laws are made for methacrylic acid telomerization with CCl₃Br and methyl methacrylate telomerization with benzenethiol as a telogen and 2,2′-azoisobutyronitrile as the initiator at 70°C. The transfer constant to CCl₃Br is ca. 0,03 and that to C₆H₅SH ca. 1,5.     

Synthèse de polysiloxanes acyloxyméthylés par réaction des acides acétique,benzoïque et méthacrylique,en présence de triéthylamine,sur des polysiloxanes chlorométhylés, 1. Synthèse et identification de trisiloxanes et tétrasiloxanes modèles

3-(Acyloxymethyl)-1,1,1,3,5,5,5-heptamethyltrisiloxanes 7b ₁, 7c ₁, 7d ₁ and 3,5-bis(acyloxymethyl)-1,1,1,3,5,7,7,7-octamethyltetrasiloxanes 7b ₂, 7c ₂, 7d ₂ ( 7b: acetoxymethyl, 7c: benzoyloxymethyl and 7d: methacryloyloxyméthyl derivatives) were synthesized from 3-(chloromethyl)-1,1,1,3,5,5,5-heptamethyltrisiloxane ( 7a ₁) or from 3,5-bis(chloromethyl)-1,1,1,3,5,7,7,7-octamethyltetrasiloxane ( 7a ₂), respectively. Spectroscopic (¹H NMR) and chromatographic (GPC and CG) characteristics of the isolated products were defined in order to standardize the analytical tools used for the study of the carboxylic acid reaction with chloromethylated polysiloxanes in the presence of triethylamine.     

Application de la réaction de métathèse à la synthèse de prépolymères α,ω-bifonctionnels. 1: Cométathèse entre le cyclooctadiène-1,5 et l'hexène-3 dioate de diméthyle

α,ω-Dimethoxycarbonyl substituted polyenes were synthesized by co-metathesis between 1,5-cyclooctadiene ( 1 ) and dimethyl 3-hexenedioate ( 2 ) by use of the catalytic system WCl₆/Sn(CH₃)₄. The ability of 2 for co-metathesis with 1 was proved by determination of the distribution of low molecular weight products in terms of reaction time and 2/1 mole ratio. For these studies, high values of 2/1 ratios (0,5–4) were chosen in order to obtain lowest molecular weight co-metathesis products ( 3b–3e ). Metathesis involved preferentially the double bonds in the neighbourhood of the ester groups. At lower values of the 2/1 ratio (0,012–0,061) α,ω-difunctional prepolymers ( 3i ) were synthesized.     

Polymérisation et copolymérisation de l'acétoxy-1 butadiène

1-Acetoxybutadiene ( 1a, b ) can be polymerized under radical conditions as well in bulk, in benzene solution or in an aqueous emulsion. Polymers consist of ca. 80% 1, 4-units ( 4 ) and 20% 3,4-units ( 5 ), as determined by use of model compounds ( 2 and 3 ). Important chain transfer reactions to monomer, which have been measured, account for low number-average molecular weights (M?_n ≈ 5000). Radical copolymerisations with acrylic, vinyl, and diene monomers indicate 1a, b to be quite similar to isoprene in these reactions. Copolymers with M?_n ≈ 20 000 are readily obtained. 1-Acetoxybutadiene polymers prepared via cationic catalysts are unstable unless careful purified. Anionic reagents are destroyed by this monomer even at ?80°C.     

Synthèse de polyquinazolones à chaîne latérale fluorée

Bis(4H-3,1-benzoxazin-4-one) substituted in 2- and 2′-position with ? CH₂CH₂R_F, where R_F is a perfluorinated alkyl group, have been prepared. Polycondensation with 4,4′-oxydianiline and with 4,4′-methylenedianiline led to polyquinazolones which have different inherent viscosities according to the solvent of polycondensation and to the proportions of reactants used. The thermal behavior of these polymers characterized by differential scanning calorimetry or thermogravimetry was studied. The polyquinazolones are thermostable and exhibit a fluorine content of 50 mass-%.     

Cinétique de télomérisation, 3. Détermination des constantes de tranfert en catalyse rédox

Three methods were used for the determination of transfer constants to the metallic complex in the telomerization reaction with redox catalysis. The first one consists in the determination of DP _n as a function of the mole ratio of telogen to monomer at the beginning of the reaction. The second one is based on the variation of the conversion degree of telogen to monomer. The last one requires the knowledge of the cumulated DP _n and the conversion degree of monomer samples during the reaction. The proposed laws were checked following the methyl acrylate telomerisation with CCl₄ as a telogen and CuCl₂ as a catalyst at 120°C. The transfer constant to CuCl₂ was found to be about 600 according to the three methods.     

Application de la réaction de métathèse à la synthèse de prépolymères α,ω-bifonctionnels, 2. Etude de possibilitiés d'application à la synthèse de prépolymères α,ω-dichlorés

The capability of chloroalkenes to undergo cometathesis with alkenes was investigated with the intention to check the possibility of applying the principle of the synthesis of α,omega;-difunctional polybutadienes to α,omega;-dichloropolybutadienes. The results obtained from the analysis of the reaction products resulting from 1,6-dichloro-3-hexene ( 1 )/4-octene ( 2 ) systems and WCl₆/EtAlCl₂ were compared with those obtained from 1-chloro-3-hexene ( 8 ) alone, 1 /1,5-cyclooctadiène ( 13 ), 5-chloro-1-pentene ( 6 )/ 2 , and 1,4-dichloro-2-butene ( 10 )/ 2 systems in the presence of WCl₆/EtAlCl₂. It was found that it is possible to apply the synthetic principle to α,omega;-bis-(δ-chloroalkenyl)polybutadienes.     

Incréments d'indice de réfraction de polymères en solution: Étude des lois de mélange. Influence de la masse moléculaire et de la structure

The variation of the refractive index increment (dn/dc) with the molecular weight and the structure of series of linear and branched well-defined polystyrenes dissolved in benzene was studied. Testing the Lorenz-Lorentz and Onsager-Böttcher mixture rules, we were able to show that:

• 1 Below a critical molecular weight of about 2·10⁴, the linear correlation dn/dc=f(1/M_n) is well explained by the influence of chemical heterogeneities included in the polymer chain (end-groups, branching points etc.).
• 2 These rules do not account for specific polymer-solvent interactions and are not quite rigorous.
• 3 The variations of (dn/dc) and the partial specific volume of the polymer, v?_p, observed already for molecular weights higher than 2·10⁴ are accompagnied by a change in the partial specific refractivity. These effects are related to the influence of intramolecular segment density in the interior of the linear or branched coil.

A homologous series of polyoxyethylene-glycols (α-hydro-ω-hydroxypoly(oxyethylene)s) in benzene presents the same behaviour.     

Halomethane-induced inhibition of protein synthesis in isolated hepatocytes

The effect of several halomethanes on protein synthesis has been studied in isolated hepatocytes. When cells are added to medium preequilibrated with CCl₄ or CBrCl₃, protein synthesis is inhibited after a lag period of 4 to 10 min. The concentrations of CBrCl₃, CCl₄, and CHCl₃ which cause a 50% inhibition of protein synthesis are about 6 μM, 400 μM, and 4mM, respectively. This order of potency parallels the rate at which these compounds are metabolized by the hepatic mixed function oxidase, suggesting that metabolism is required for toxicity. The inhibitory effect caused by 18 min of exposure to CBrCl₃ is not reversed when the toxin is removed, indicating that inhibition involves some irreversible modification of cellular material. Unexpectedly, the inhibitory effect caused by 18 min of exposure of CCl₄ is about 30–40% reversed when the toxin is removed. This suggests that CCl₄ causes inhibition not only by a metabolism-dependent (irreversible) pathway, but by a metabolism-independent (reversible) mechanism as well. Extracellular Ca²⁺ is not required for CCl₄ inhibition of protein synthesis.     

Propriétés rhéologiques à l'état fondu de mélanges binaires de polyéthylène et de polybutène-1

The dynamic rheological study on a series of binary blends obtained from low-density polyethylene and poly(1-butene) was carried out. From our results we can propose an analogical pattern which is able to simulate the rheological behaviour of the blend in the melt state. We have calculated the different parameters of the model and their variations with temperature, composition, mixing and frequency. We have demonstrated that:

• The viscosity η₀ and the mean relaxation time τ₀ decrease with increasing temperature, while the parameter h of the distribution of relaxation times remains independant of the temperature.
• Kneading operation gives rise to a drop of the τ₀, η₀ and h values compared to those products which have not been kneaded.
• The viscosity η₀ is the weighted sum of the blend components.
• The viscosity η₀ of the blend is a function of the molecular weight.

     

Dégradation de polybutadiènes par métathèse avec l'hexène-3 dioate de diméthyle

Studies of metathetic degradation of polybutadienes containing 70 to 80% of 2-butene-1,4-diyl units ( 1 ) in presence of dimethyl 3-hexenedioate ( 2 ) were carried out applying WCl₆/Me₄Sn as catalyst and r = [ 2 ]/[ 1 ] values varying between 0,4 and 0,01. The degradation was followed by steric exclusion chromatography, and the structural composition of degraded products was determined by ¹H NMR. For r = 0,2, the degradation by cross metathesis between 1 and 2 , leading to α,ω-bifunctionalized “prepolymers”, is superimposed by degradation via intramolecular metathesis and cationic cyclization of 1 units. Cationic side reactions (cyclization) are minimized by addition of ethyl acetate to the catalytic system.     

Synthèse de macromères à base de chlorures de vinyle et de vinylidène au moyen de télomères

New macromers 4, 8, and 10, containing ester, alcohol, or acid functions, were prepared starting with vinyl chloride (CV) or vinylidene dichloride (CV₂). The telomer 1, resulting from CV₂ and CCI₄ was telomerized with allyl acetate and the product was transformed into the acrylate 4 by hydrolysis of the reaction product and subsequent esterification. Macromers 8 and 10 were prepared from CV by radical telomerization with thioglycolic acid (7) and 2-mercaptoethanol (9), respectively. Reactive double bonds were introduced into these macromers by reaction with acrylic acid, Vinyl chloroformate, methacryloyl chloride, or 2,3 -epoxypropyle methacrylate, leading to new macromers 12, 13, 14, and 15, respectively.