Photo-oxydation de polyéther-block-polyamides

Analytical and kinetic aspects of the photooxidation in the solid state of two polyether-block-polyamides 1a and 1b are described. The block copolymers studied contain different fractions of polyether segments. Nevertheless, their photooxidation presents the same features and concerns mainly the ether groups. In both thermoplastic elastomers, 1a and 1b very high stationary concentrations of hydroperoxy groups ? CH(OOH)? O? CH₂? are observed (0,3 to 0,7 mol · kg^?1). These hydroperoxides are, however, photounstable and thermounstable above 60°C. They are converted into hemiacetals ? O? CH(OH)? O? CH₂? , saturated esters and formates. The hemiacetal groups are thermounstable, too, and decompose into alcohol and aldehyde groups, the latter being photoxidized in the matrix. The oxygen consumption rate, the primary hydroperoxidation rate, and the rate of accumulation of final products were determined. A mechanism including the photolysis and the thermolysis of the hydroperoxides can account for the formation of the final photoproducts (hemiacetals, esters, formates and acids).     

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.     

Synthèse et transformations chimiques des télomères de l'undécène-10 oate de méthyle, 1

Redox of radical telomerizations of methyl 10-undecenoate (1) with different telogens such as CCl₄, CCl₃Br, CCl₃CF₃, HPO (OEt)P₂ or different adducts of CCI₄, on vinylidene chloride and chlorotrifluoroethylene, were studied. Chemical transformation of the end of the chains led to the corresponding difunctional compounds. Starting with these last compounds, polycondensation reactions were carried out.     

Photo-oxydation des polyéther-bloc-polyamides, 2. Influence de la composition des polymères multiséquencés

Analytical and kinetical aspects of the photooxidation in the solid state of two polyether-block-polyamides 1c and 1d are described. The block copolymers studied contain different polyether sequences at different percentages. In copolymer 1d as well as in copolymers 1a and 1b , previously studied, the photooxidation concerns mainly the ether groups. High maximal concentrations of hydroperoxy groups, ? CH(OOH)? O? CH₂? , are observed (0,12 mol.kg^?1). These hydroperoxides are converted into hemi-acetals, ? CH(OH)? O? CH₂? , saturated esters and formate through photolysis or thermolysis above 60°C. The hemi-acetal groups are thermo-unstable too and decompose into alcohol and aldehyde groups. The photooxidation of copolymer 1c presents different features. At long wavelengths, low stationary concentration of hydroperoxy groups are observed (0,02 mol.kg^?1). Hydroperoxidation of the polyamide 6 sequences is revealed by the formation of imide groups. Hydroperoxidation of the poly(propylene glycol) sequences are surprisingly located on the ether methylene groups. Excitation of polyamide 6 sequences at short wavelength (254 nm) induces the formation of crotonized aldehyde groups.     

Photolytisch induzierte umsetzungen chlorhaltiger systeme in lösungen mit polystyrol

UV spectroscopic measurements to identify the products of photolysis in polystyrene solutions of CCl₄ and CHCl₃ as a function of the atmospheric oxygen concentration are conducted. In polystyrene chains C?C bonds are formed, thus changing the absorption properties in the long wave length range. The concentration of induced C?C bonds is higher in CCl₄ solution than in CHCl₃ solution. The effect of O₂ is observable for pressures p ≥ 2 · 10^?1 mmHg; it is of minor importance for the formation of C?C bonds, however. On the low-molecular-weight side COCl₂, Cl₂, and HCl are the photolysis products in the presence of O₂. Observable changes in the absorption of the solvent at 280 nm were attributed to the electronic n ← π* transition of the carbonyl groups of COCl₂, whereas the newly created broad band in the UV spectrum of the solvent was attributed to the electronic ¹ Π_1u ←¹Σ _g⁺ and ³Π⁺_ou ← ¹Σ_g⁺ transitions in Cl₂. The first of these transitions is responsible for the dissociation of Cl₂ molecules. A hypothesis has been set forth that molecular oxygen affects the probability density of the electronic ³Π_ou⁺ ← ¹Σ_g⁺ transition. The concentration of O₂ has a substantial effect on the concentration of the COCl₂ photoproducts, which is best displayed by the molar absorption coefficient of this compound.     

Etude par 1H NMR des groupements chlorométhyles du poly(chlorure de vinyle), 2. Etude par écho de spin et comparaison avec des modèles moléculaires

In order to assign all ? CH₂Cl resonances observed by ¹H NMR in poly(vinyl chloride), (PVC), a preliminary study of the diastereoisomers of molecular models for the groups CH₂Cl? CHCl? [II] and is used, in conjunction with spin echo experiments. The complex region [3,5–4,0 ppm] which corresponds to saturated ? CH₂Cl chloromethyl protons is completely assigned. A separate evaluation of ? CHCl? CH₂Cl [II], ? CH₂? CH₂Cl [III] and is proposed and tested on raw PVC samples. The main interest of this ¹H NMR determination is the fact that raw PVC can be used and that it gives the ratio [II]/[III] which is not accessible by ¹³C NMR on reduced samples.     

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.     

Structures et propriétés diélectriques des poly(α-acétoxystyréne)s parasubstitués

The relations between structure and isothermal, dielectric properties of poly(α-acetoxystyrene)s substituted in para position by ? OCOCH₃ ( 1a ), ? OCOCH₂CH₃ ( 1b ), ? OCOCH₂CH₂CH₃ ( 1c ), ? OCOC₆H₅ ( 1d ), ? OCOCH₂CH₂Cl ( 1f ) and ? OCOOCH₃ ( 1g ) were studied. The dielectric constants, at 10⁵ Hz and 20 ± 2°C, were found to be: 3,79 ( 1a ), 3,36 ( 1b ), 3,18 ( 1c ), 3,51 ( 1d ), 3,36 ( 1e ), 3,65 ( 1f ) and 3,07 ( 1g ). The polymers 1a – 1g do not show any α- or β-transition. Increasing bulkiness of the para substituent gives rise to a decreasing dielectric constant due to an increase of the degree of syndiotacticity, as determined from ¹H and ¹³C NMR spectra.     

Homo‐ and Copolymerization of ω‐Functional Polystyrene Macromonomers via Coordination Polymerization

Macromonomers have been extensively used, as well defined building blocks for various macromolecular architectures via anionic, ROMP and free radical homo‐ or copolymerization processes. The purpose of the present work was to examine the homopolymerization and copolymerization of ω‐allyl, ω‐undecenyl and ω‐vinylbenzyl polystyrene (PS) macromonomers, in the presence of early or late transition metal catalysts. The influence of several parameters (type of catalytic system, nature of polymerizable end‐group and molar mass of the macromonomer) on the homopolymerization was first investigated. Whereas ω‐allyl or ω‐undecenyl PS macromonomers were not very reactive in homopolymerization whatever the catalyst, ω‐vinylbenzyl PS macromonomers gave interesting results with CpTiCl₃/MAO and Cp*TiCl₃/MAO. The copolymerization of these macromonomers with ethylene was also studied in the presence of the following palladium catalyst: [(ArN?C(Me)? C(Me)?NAr)Pd(CH₂)₃(COOMe)]⁺BAr₄′^?(VERSIPOL?) (Ar = 2,6‐iPr₂–C₆H₃ and Ar′ = 3,5‐(CF₃)₂? C₆H₃). ω‐vinylbenzyl PS macromonomers could not be incorporated into poly(ethylene) chains. On the contrary, the incorporation of ω‐allyl PS macromonomers was achieved. Moreover, for macromonomers containing an alkyl spacer between the allylic unit and the PS chain, the incorporation rate, the copolymerization yield and the molar masses of the copolymers were increased, giving access to a new type of graft copolymer structure.

Synthesis of polystyrene macromonomers.     

Nouvelle préparation de polychlorophosphazènes linéaires

Polychlorophosphazenes 2 can easily be obtained by thermal condensation of dichlorophosphinoyliminotrichlorophosphorane ( 1 ) under atmospheric pressure at 240–290°C, pure POCl₃ being eliminated. The different stages of the reaction were studied by chemical analysis, ³¹P NMR, IR spectroscopy, and thin layer chromatography. The procedure enables one to obtain polymers of low and high molecular weights. The samples do not contain any cyclic or reticular polymers. Species of low molecular weights can be separated from those with high molecular weights by treatment with heptane. The total yield of phosphorus is 100% with regard to the starting material. Substitution products (Cl by OCH₂CF₃) are obtained which are identical with those obtained with the polychlorophosphazenes prepared via classical methods.     

Photo-oxydation de résines phénoliques

Analytical and kinetic aspects of photo-oxidation in the solid state of phenolic resins (phenolformaldehyde polycondensates) are described. On the basis of Fourier-transform infrared analysis it should be noted that resins contain, in addition to methylene-bridged structures, ether linkages (? CH₂? O? CH₂) between aromatic structures. Photochemistry of the phenolic resins involves two primary processes. Photolysis of the phenolic groups leads to the formation of quinone methide structures and photo-oxidation of the dimethylene ether linkages to hydroperoxy groups which are photo- and thermo-unstable. These hydroperoxy groups are converted into ester and formate groups.     

The initiation of polymerization of unsaturated tertiary amines with carboxylic acids

The polymerization rate (R_p) of N-methyl-N-phenyl-2-aminoethyl methacrylate (MPAEMA) initiated with 2,2' -azodiisobutyronitrile (AIBN) at 50°C increased considerably after the addition of CCI₃COOH, and distinctly after the addition of CH₃COOH. R_p in a benzene solution of 2 mol. dm^?3 MPAEMA and 5 · 10^?2 mol. dm^?3 CCl₃COOH (without AIBN) was 13% · h^?1. [η] of the obtained polymer corresponded to 64 cm³ · g^?1. The polymerization order of MPAEMA initiated with CCl₃COOH is 0,93 with respect to monomer and 0,51 with respect to CCl₃COOH. The overall activation energy of polymerization of MPAEMA calculated from the temperature dependence of R_p between 20 and 50°C is 43 ± 1,2 kJ · mol^?1. In a benzene solution of 2 mol.dm^?3 MPAEMA, 5 · 10^?2 mol · dm^?3CCl₃COOH and 5 · 10^?3 mol · dm^?3 1,4-benzoquinone at 50°C the polymerization does not proceed for 6 h. In a benzene solution of 2 mol · dm^?3 4-dimethylaminostyrene (4-DMAS) and 2 mol · dm^?3 CH₃COOH (without AIBN), 40% of monomer polymerized within one hour. [η] of the polymer was 4 cm³ · g^?1. The overall activation energy of polymerization of 4-DMAS in the presence of CH₃COOH is ca · 54 kJ · mol^?1. The addition of 5 · 10^?3 1,4-benzoquinone slows down the polymerization rate only slightly. The effect of acids on the elementary polymerization reactions is characterized.     

Etude par résonance magnétique nucléaire du 1H et 13C des télomères du chlorure de vinyle et du tétrachlorure de carbone

The adducts and bi-adducts of the reaction of vinyl chloride with carbon tetrachloride, CCl₃ (CH₂CHCl)_n Cl and Cl (CHClCH₂) CCl₂ (CH₂CHCl)_p Cl respectively, have been studied by ¹³C and ¹H NMR. The identification of the characteristic peaks of each product enables of much better control of the purity of the telomerization reactions. Moreover, it was possible to resolve complex spin systems in ¹H NMR (up to 9 non-equivalent spains). In particular the threo and erythro conformation of the tri-adducts could be assigned without any ambiguity. Thanks to model molecules, the chemical shifts were specified in ¹³C NMR for all carbon atoms with similar groups.     

Etude de la dégradation thermique de deux copolymères réalisés entre l'acrylonitrile ou le méthacrylonitrile et l'α-acétoxyacrylate de méthyle. Analyse thermogravimétrique et chromatographique en phase gazeuse couplée à la spectrométrie de masse

The thermal degradation behaviour of two copolymers poly(acrylonitrile-co-methyl α-acetoxyacrylate) and poly(methacrylonitrile-co-methyl α-acetoxyacrylate) was studied by means of dynamic and isothermal thermogravimetry in the range 246–302°C and gas chromatography/mass spectrometry analysis. The main volatil products are acetic acid and methyl acetate and methanol in minor amounts. There is no monomer from the first copolymer. The global reaction order is zero over a wide range of conversion (α = 0,1 – 0,6), then it is one for α > 0,7, with activation energies of 160,5 and 142,9 kJ ˙ mol^?1, respectively. Some amount of comonomers was found in addition in the case of the second copolymer. The kinetic law may be written as: where A and C are constants for every temperature. The global activation energy was found to be 127,0 kJ ˙ mol^?1. A kinetic model of a one order reaction with a partial auto catalytic character allows a very good fit of the experimental data with the theoretical curves over a wide range of conversion (α = 0,1–0,8).     

Production of organometallic polymers by interfacial technique, 33.. Synthesis of oligomeric cobalticinium containing dialkylstannanediyl polyesters

Oligo(oxycarbonyl-1,1′-cobalticendiylcarbonyloxydialkyl (or diaryl)stannanediyl hexafluorophosphate)s ( 3 ) were synthesized by condensation of alkali salts of 1,1′-dicarboxycobalticinium hexafluorophosphate ( 2 ) with dialkyl (or diaryl) tin dihalides in CCl₄/water using the interfacial technique. Variation of the halide and of the alkyl or aryl group causes an increase of the yield in the order I≈Br > Cl and C₆H₅? > H₂C?CH? >(CH₃)₃CH? > C₂H₅? >H₃C(CH₂)₇ ? ≈ C₆H₅CH₂? > CH₃ The polymeric product ( 3 ) undergoes an exchange of the hexafluoro phosphate ion in a suitable aqueous salt solution to give soluble products.     

Cinétiques de télomérisation, 7. Calcul de k/kTe en polymérisation radicalaire de divers monomères

In contrast to the usual method of determination of the principle ratio in radical polymerization, k/k_Te, which is based on the comparison of the rate of polymerization with the concentration of initiator, a method was used consisting in the representation of log_e([M]₀/[M]) versus (1 ? e^?kd^t/2). The results obtained with styrene, vinyl acetate, acrylic acid, methacrylic acid, and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate ( 1 ) were found to be in good agreement with those already obtained by the other method.     

Poly{[(Chloro-2 éathyl)-4 phéanyl]-1 éathylène}: Synthèse,caractérisations,dégradation thermique et modifications chimiques

Poly{1-[4-(2-chloroethyl)phenyl]ethylene} ( 3 ) was synthesized by bulk polymerization of 4-(2-chloroethyl)styrene ( 6 ) in two steps from commercial products. The polymer was characterized by means of GPC (weight-average molecular weight M?_w = 85 000 and number-average molecular weight M?_n = 63 500), ¹H NMR and ¹³C NMR spectroscopy. The first stage of thermal degradation begins at 290°C and ends at about 410°C. The overall activation energy was calculated to be 43 kcal · mol^?1 (180 kJ · mol^?1). The solid residue was crosslinked and insoluble. The volatile products, identified by gas chromatography-mass spectroscopy (GC-MS), were chiefly hydrogen chloride, dichloromethane and monomer. In a strongly basic medium, nucleophilic substitution of chlorine was achieved without elimination.     

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.     

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 et propriété d'échange anionique de quelques résines de type N-(dialkylaminométhyl)-acrylamide

Copolymerisation of N-(dialkylaminomethylacrylamides) ( 7a–e ) with divinylbenzene led to anion exchange resins. The monomers 7a–e were prepared by reaction of acrylamide with mixtures of paraformaldehyde/dialkylamine ( 2 ). The anion exchange properties of the resins were studied and it was found that the rate of H⁺ fixation is slow, whereas the exchange between two anions is fast. The affinity scale of the anions used was found to be: Cl^?<Br^?<I^?<NO^?<SCN^?<ClO^?, which is quite similar to that observed with quaternary ammonium polystyrene resins. The selectivity constants increase with the number of C atoms of the amines. The selectivity, which is low for methyl or ethyl substituents, becomes similar or higher than of commercial analytical resins for the polymer derived from dihexylamine. The hydrophobic character of the dialkylamine groups results in a high stability of anion-cation association for anions of low hydration energy. These features allow an interpretation of the observed properties.