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.     

Étude de la polymérisation du styrène en émulsion inverse

The polymerization of reversed emulsions water in styrene prepared with polystyrene-polyethyleneoxide block copolymers (Cop PS-POE) has been studied. The kinetics of this polymerization has been studied as a function of the parameters: type and concentration of initiator, phase ratio water/styrene, concentration of Cop PS-POE, molecular characteristics of Cop PS-POE. The type of the emulsion can be regulated by the characteristics of the Cop PS-POE and by the phase ratio water/styrene. The initiation of the polymerizations can be achieved by water soluble initiators (K₂S₂O₈). Correlations could be established between the rate of polymerization and the initiator concentration, the amount of water in the reversed emulsions and the concentration of Cop PS-POE. It was shown furthermore that the rate of polymerization increases with the POE content of two-block copolymers and that three-block copolymers are more appropriate for the polymerization in reversed emulsions. Finally the main influence of the water/styrene interface was demonstrated which regulates the transfer of radicals from the aqueous into the organic phase.     

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-%.     

Synthèse,polymérisation et copolymérisation d'un dérivé 2h-benzotriazolylphényl de l'acétate de vinyle

1-(4-Acetoxy)-3-(2H-benzotriazolylphenyl)vinyl acetate (4) was synthesized. The polymerization of 4 afforded polymer 5 with a relatively low molecular weight (= 2000). Copolymerizations of 4 (3,7 wt.-%) were carried out with styrene and methyl methacrylate to copolymers 6 and 7, respectively. Polymer 5 and copolymers 6 and 7 were characterized by ¹ H and ¹³ C NMR and by IR and UV spectroscopy. Their UV spectra show a strong absorption in the near UV spectrum. 4 may thus be considered as a potential comonomer for UV protection.     

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.     

Etude de la réaction de télomérisation d'un monomère tensioactif anionique

The synthesis of a new anionic polymerizable surfactant is described. It is obtained by reaction between methacryloyl chloride and 5-phenyl-1-pentanol. In a last step, the aromatic group is alkylated with succinic anhydride in order to obtain an ionic group. All products were characterized by ¹H nuclear magnetic resonance and the transfer constant C_T with C₈H₁₇C₂H₄SH and the ratio k_p²/k_t were determined. C_T is in agreement with that of classical acrylates whereas k_p²/k_t is lower because of the long methacryloyl chain which reduces the propagation rate.     

Détermination des masses et des distributions moléculaires d'un poly(aryléthercétone-co-sulfone) semi-cristallin (HTX) à l'aide d'une méthode de dérivatisation chimique, 1. Caractérisation moléculaire du HTX en solution dans l'acide sulfurique concentre

HTX, a poly(aryletherketone-co-sulfone), is characterized in solution in concentrated sulfuric acid. Upon dissolution in concentrated H₂SO₄, HTX is chemically modified by sulfonation of phenyl rings. The modification of the chemical structure is studied with a model compound by means of IR spectroscopy. The increase of the molar mass corresponding to a complete sulfonation is determined by means of mass spectrometry. Light scattering and ¹⁹F NMR measurements are performed in order to obtain the weight- (M?_w)_s and number-average (M?_n)_s molar masses of sulfonated HTX samples. (M?_w)s values allow the determination of the Mark-Houwink-Sakurada relationship for HTX in 99,5% H₂SO₄ at 25°C.     

Préparation et caractérisation des poly(o-chlorométhylstyrène), poly(m-chlorométhylstyrène) et poly(p-chlorométhylstyrène). Etudes des résonances magnétiques nucléaires 1H NMR et 13C NMR. Application à l'étude d'une résine de type merrifield

Ortho-, méta- and para-chloromethylstyrene were polymerized and their ¹H NMR and ¹³C NMR spectra were studied. The knowledge of the chemical shifts, especially those in ¹³C NMR, allows the analysis of poly(o--chloromethylstyrene-co-m--chloromethylstyrene) and of a Merrifield-type resin which was prepared by a terpolymerization reaction of styrene, chloromethylstyrene and divinylbenzene.     

Synthèse et caractérisation de polystyrènes siliciés

Poly(p-trimethylsiloxystyrene) (1a) , poly[p-(tert-butyldimethylsiloxy)styrene] (1b) , poly[p-(trimethylsiloxy)-α-methylstyrene] (1c) , poly[p-(tert-butyldimethylsiloxy)-α-methylstyrene) (1d) and poly{p-[2-(tert-butyldimethylsiloxy)ethyl]styrene]} (1e) were prepared by free-radical or cationic polymerization of the corresponding monomers. Poly{[p-[2(trimethylsiloxy)ethyl]styrene]-co-[p-(2-hydroxyethyl)styrene]} (2a) was synthetized by anionic polymerization of the corresponding trimethylsilylated monomer, followed by acid hydrolysis of the resulting polymer. Poly{[p-[2-(trimethylsiloxy)ethyl]styrene]-co-[p-(tert-butoxycarbonyloxy)styrene]} (2b) were prepared by free-radical polymerization of the corresponding monomers.     

Etude comparée des propriétés mécaniques dynamiques des formes I et II du polybutène-1. Cinetique de transformation II → I

The behaviour of the molecular motion in synthetic cis- and trans-1,4-polyisoprenes was studied by nuclear magnetic resonance. The line-widths (ΔH_pp), second (M₂) and fourth moments (M₄) of the absorption curves were measured at 77, 4.2, and 1.3 K. The obtained values of ΔH_pp and M₂ for cis-polyisoprene indicate that the molecular motions are apparently not completely quenched at 77 K since there is a further increase in the values of M₂ and ΔH_pp when decreasing the temperature from 77 to 4.2 K. It was found also that the value of M₂ at 4.2 and 1.3 K (? 20 G²) was larger than the previously computed one for a rigid lattice (18.5 G²). The temperature dependence of M₂ and ΔH_pp for trans-polyisoprene is different from that for cis-polyisoprene. The values of M₂ are constant in the range from 77 to 1.3 K (? 19.5 G²), which suggests that the molecular motion is presumably stopped in this polymer already at 77 K.     

Oligomères amphiphiles obtenus par voie radicalaire, 1. Synthèse et caractérisation d'oligomères de l'acide acrylique à extrémité dodécylthio

Oligomeric emulsifiers were prepared by the technique described by Roe, with special care of composition and molecular weight. Acrylic acid was polymerized in 2-propanol with lauroyl peroxide as initiator in the presence (at various ratios) of 1-dodecanethiol ( 8 ) as transfer agent to control the chain length. A good agreement was found between the various methods used for kinetic determination and oligomer characterization (¹H NMR, sulfur analysis, vapor pressure osmometry, acidimetry, GPC). Values of k_pk_t^-1/2, transfer constants for thiol 8 and solvent, nature of chain ends, polydispersity, and molecular weight were determined. Polymer fractionation was successfully performed using different solvents for recovery.     

Volumes spécifiques de polystyrènes en étoile à l'état liquide

Specific volume measurements carried out on linear and star-shaped liquid polystyrene versus the number average molecular weight, M_n scaling between 5000 and 2.10⁶, are in good agreement with a review of the experimental results of others. These results confirm the occurrence of a loss of volume per monomeric unit above a molecular weight of 10000 already observed for polystyrene in solution. We attribute the influence of this specific volume variation against M_n on the thermal dilatometric coefficient α = (1/v)dv/dT and the temperature of vitrous transition. We also attempted to give an explanation for this phenomenon.     

Télomérisation en milieu aqueux, 2. Étude cinétique de la télomérisation de l'acide acrylique avec l'acide thioglycolique

The telomerization of acrylic acid with thioglycolic acid initiated with hydrogen peroxide in aqueous medium is presented. In order to better control this reaction, the decomposition of H₂O₂ was first investigated by means of differential scanning calorimetry (DSC), leading to a very high value of the dissociation rate constant (k_d), and then studied by volumetry in the presence of a mercaptan. This second method gave a higher value of k_d (by about 6 orders of magnitude at 50°C). From the latter value, the ratio fk_P²/k_Te and the transfer constant of thiogiycolic acid, C_t, were determinated and compared with those reported in the literature. The kinetical parameters, obtained from theoretical and experimental values of DP _n and the conversion of the monomer are in good agreement and allow to prepare telomers of acrylic acid with controlled chain length.     

Synthèse et étude de copolymères sequencés photochromiques

New photochromic polymers were prepared by deactivating living homo or block copolymers with various 2H-chromene-2-spiro-2′-indolines ( 3a–3d ). Classical anionic polymerization was used throughout this work. By varying the chemical nature of the blocks as well as that of the photochromic units, a series of novel materials was obtained and their structure and behaviour were characterized.     

Terpolymérisation acrylonitrile-styrène-acrylate de méthyle, 4. Copolymérisation en emulsion styrène-acrylate de méthyle en réacteur fermé (batch) en présence de persulfate de potassium

To improve the knowledge of emulsion copolymerization of monomers both swelling their copolymers, but which are of quite different polarity (water solubility), a series of styrene (S)/methyl acrylate (MeA) copolymerizations was carried out in batch at 50°C with potassium persulfate as initiator. The overall rates of copolymerization increase with the amount of MeA in the monomer feed. Copolymer composition follows the usual copolymerization equation if bulk/solution reactivity ratios (r_ij) and monomer partition between aqueous and organic phase are taken into account (simulation). However, accurate kinetic data at low conversion (gas chromatography) put in evidence an enhanced polymerization of the more hydrophilic monomer (MeA), which can be attributed to polymerization in the water phase. Particle sizes increase with conversion and tend to a limiting value, the higher the MeA content is. Particle number (N_p), which is practically constant with conversion of S homopolymerization, tends to increase with MeA content as polymerization proceeds. This trend is enhanced if the emulsifier (sodium dodecanesulfonate, SDS) concentration is increased. Overall propagation rate constants were estimated as function of the experimental conditions and monomer concentration within the particles. From kinetic data (rate of polymerization) and N_p, it was found that the average number of radicals per particle, ñ, remains close to 0,5. It was then possible considering S(k_p = 125 1 · mol^?1 · s^?1) as a standard monomer, to estimate the polymerization rate constant for MeA (335 1 · mol^?1 · s^?1). Since adsorption of emulsifier was shown to be closely related to particle surface composition, the specific area A_s of SDS was measured on latices at various conversions and initial monomer feeds. As conversions increases, the particle surface appears to be richer and richer in MeA, which corresponds to a particle structuration. Strong and weak acid group titration is also in quite good agreement with the colloidal behaviour.     

Synthèse et copolymérisation avec l'acrylamide de macromonomères d'acrylate de dodécyle

Graft copolymers of well-defined structure and composition were prepared by radical copolymerization of acrylamide and poly(dodecyl acrylate) macromonomers. The macromonomers were prepared by telomerization of dodecyl acrylate in the presence of 2-mercaptoethanol as a transfer agent, followed by reaction with acryloyl chloride. Poly(dodecyl acrylate) macromonomers with M _n = 1100, 1100, 2200 and 4600 were synthesized. The kinetics of the radical telomerization of dodecyl acrylate with 2-mercaptoethanol and AIBN was studied at 66°C in THF. Under these conditions we obtained the transfer constant C_T = 0,9. The graft copolymerization of acrylamide with the poly(dodecyl acrylate) macromonomer was carried out in the presence of the transfer agent C₆F₁₃C₂H₄SH. If C₀ = [AIBN]/[Acrylamide] = 0,01 and R₀ = [C₆F₁₃C₂H₄SH]/[Acrylamide] = 0,01, for acrylamide a DP _n = 160 was obtained in all cases, for the macromonomer of M _n = 1100 a DP _n = 2,5, and for the macromonomer of M _n > 1100 a DP_n = 1.     

Synthèse et polymérisation de monomères acryliques fluorés substitués en position α, 4. Applications à l'α-acétoxyacrylate et à l'α-propionyloxyacrylate de 2-perfluorooctyléthyle

The synthesis of the two monomers 2-perfluorooctylethyl α-acetoxyacrylate ( 1 ) and 2-perfluorooctylethyl α-propionyloxyacrylate ( 2 ) was performed in two steps starting from ethyl pyruvate and 2-perfluorooctylethanol with overall yields of about 56% and 50%, respectively. Transesterification of ethyl pyruvate with the adequate fluorinated alcohol followed by enol acylation gave 1 and 2 , respectively. The kinetic study of polymerization of monomers 1 and 2 , led to the determination of the values of the ratio of the square of the rate constant of propagation over the rate constant of termination k²_p/k_te equal to 9,2 · 10^?3 and 9,1 · 10^?3 L · mol^?1 ·s^?1, respectively, and were compared to those of commercially available fluorinated acrylates and methacrylates.     

Etude de la réaction de télomérisation d'un monomère tensioactif cationique

A polymerizable methacrylic surfactant is synthetized from methacryloyl chloride and 11-bromoundecanol. The obtained cationic monomer is telomerized with a fluorinated thiol, and the transfer constant C_T is calculated. This value is in the same range as transfer constants of classical methacrylic monomers. The obtained k_p²/k_T is low because of the long chain ester. Polymers were prepared in homogeneous solution with an average molecular weight of 25 000.     

Influence des traitements thermiques à l'état fondu sur les cinétiques de cristallisation du poly(oxyméthylène)

The influence of the temperature of the melt T₁ on the kinetics and the morphology of a semicrystalline polymer (poly(oxymethylene)) was investigated using thermal analysis and optical microscopy. The thermodynamic melting point T and the enthalpy of melting at thermodynamical equilibrium ΔH were determined by extrapolation of the graphs T_f = f(T_c) and ΔH_f = f(T_c); (T = 198°C, ΔH = 251 J/g). For different temperatures of the melt (T₁ = 185°C, 195°C, 205°C), isothermal and non-isothermal crystallizations were analysed using the Avrami and Ozawa equations. Nucleation and spherulitic growth in this polymer were studied by using optical microscopy at elevated temperatures. Using different analyses, we observed initial nucleation followed by spherulite growth with the following influence of the temperature of the melt on the distribution and the number of spherulites: T₁ < T produces many small spherulites; T₁ > T gives rise to few large spherulites.     

Effect of UV light on the system styrene/maleic anhydride at −196°C

The effect of UV light (λ > 300 nm) on the system styrene/maleic anhydride/solvent (acetone or chloroform) in the presence and/or absence of the alternating styrene/maleic anhydride copolymer was studied by the ESR method at ?196°C. It was found that the concentration of paramagnetic species increased with the time of irradiation. The intensity of the ESR spectra at ?196°C did not change when the light was cut off. By analysis of the ESR spectra of the systems studied the methyl (a_H = 2,3 mT), dichloromethyl (a_H = 1,66 mT), and acetyl (a_H = 0,52 mT) radicals as well as the radicals A and D (a_H^α = 2,25 mT, a_H^β = 3,19 mT) and (a_H^β = 1,1 mT), respectively, were identified.