Polystyrènes à motifs bifonctionnels: synthèses,caractérisations et modifications chimiques

Four enol esters with a styrene skeleton ( 3a – d ) were synthesized in two steps from commercial products and polymerized or copolymerized with styrene as a comonomer. The polymers and copolymers ( 7 and 8 ) were characterized. They are stable up to 140°C and lose acetic acid upon heating. Chemical modifications, such as nucleophilic substitutions with cyanide ions or nucleophilic addition of butyllithium, were studied.     

Etude de la dégradation thermique du poly{acétoxy-1 [(chloro-2 éthyl)-4 phényl]-1 éthylène}

A kinetic study of the thermal decomposition of poly{1-acetoxy-1-[4-(2-chloroethyl)phenyl]-ethylene} ( 1 ) was carried out by thermogravimetry. Two stages, well separated, are observed. The first one begins at 140°C. The corresponding decomposition reaction is a superposition of two reactions: loss of acetic acid and partial depolymerization. The main volatile products released in this first stage, identified by gas chromatography/mass spectrometry coupling, are chiefly acetic acid and a small quantity of p-(2-chloroethyl)acetophenone; there is no monomer from the monomeric unit. As in case of other poly(para-substituted α-acetoxystyrenes) the solid residue is poly[p-(2-chlorethyl)phenylacetylene] ( 5 ) of low molar mass, soluble in all usual organic solvents. No auto-catalytic mechanism was found during this first stage, unlike in case of poly(vinyl acetate). The reaction order is one, over a wide range of conversion. The activation energy was found to be about 145,6 kJ/mol and the pre-exponential factor 1,6 · 10¹⁵ min^?1. An explanation for the insolubility of the residues, obtained by thermal degradation of some poly(p-chloroalkylstyrenes), is proposed.     

Synthèse et caractérisation de réticulats-modèle de polyisoprène

Polyisoprene model-networks were synthesized by an “endlinking” process: an efficient bifunctional initiator, developped recently, was used to polymerize isoprene to a bifunctional “living” precursor polymer. The living sites were subsequently used to initiate the polymerization of a small amount of divinylbenzene, whereby a model network is formed, the elastic chains of which are of known length and low polydispersity. Equilibrium swelling data and stretching moduli were measured. Unfortunately no reproducible results could be obtained on unswollen networks. Qualitative experience was obtained on the degree of association of lithium organic sites in benzene solution: the value of 2 is to be considered as plausible.     

Copolymères séquencés polystyrène/polyvinyl-4 pyridine: Synthèse,caractérisation et étude des phases mésomorphes

Macroporous polymers based on 2-hydroxyethyl methacrylate and crosslinked with ethylene-bismethacrylate were prepared by radical copolymerization in the presence of solvents. Toluene was used as an inert component, and its concentration range for the rise of macroporosity was determined. The influence of concentration of both the inert component and the crosslinking agent on the mean size of pores was established. The mechanical properties of the copolymers were compared with FRENKEL 's sinter theory.     

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.     

Copolymères greffés: Poly(méthacrylate d'alkyl-g-oxyde d'éthylène), 1. Synthèse et caractérisation

It was shown that it is possible to synthesize fairly homogeneous graft copolymers the grafts of which are able to crystallize. The grafting was achieved by transesterification. The terminal potassium alcoholate group of a poly(ethylene oxide) (prepared by polymerization of oxirane with diphenylmethylpotassium) reacts with the ester functions of a poly(propyl methacrylate) or a poly(butyl methacrylate). The reaction was performed at 110°C in toluene solution, in a glass reactor sealed off under vacuum. To characterize the products, ultracentrifugation, Kössler-Polǎ?ek fractionation, nuclear magnetic resonance, flash pyrolysis combined with gas chromatography, osmometry, and light-scattering were used.     

Synthèse et caractérisation de copolymères séquencés polystyrène/polydiméthylsiloxane et polyisoprène/polydiméthylsiloxane

Polystyrene/polydimethylsiloxane and polyisoprene/polydimethylsiloxane block copolymers were synthesized by anionic polymerization in cyclohexane (styrene and isoprene) and in a cyclohexane-diglyme mixture (hexamethylcyclotrisiloxane) with the use of sec-butyllithium as initiator. Polymers have been fractionated from benzene solution by progressive addition of methanol. Gel permeation chromatography (GPC), light scattering, osmometry, and elementary analysis were used to characterize the fractions. Copolymers, thus prepared, are free of homopolymers and the polydispersity of molecular weight and composition of the fractions is very low.     

Modification des condensats phénoliques par des groupes phtalimides. Résines dérivées des phtalimidométhylphénols. Synthèse et caractérisation

By reacting N-hydroxymethylphthalimide ( 5a ) or N-chloromethylphthalimide ( 5b ) with an excess of phenol, a mixture of 2-phthalimidomethylphenol ( 6 ) and 4-phthalimidomethylphenol ( 7 ) was obtained. The ratio 6/7 was found to be 2:3 for the reaction with 5a and 3:2 with 5b , as determined by ¹H NMR at 250 MHz. The condensation of 6 with hexamethyleneteraamine ( 3 ) at the mole ratio 6/3 equal to 2 and 7,5 was performed at 190°C. The resulting resins (H? PP) were compared to those prepared from o-cresol and 3 (H? OC), and GPC of the resulting products was made. A higher thermal stability of the resins H? PP was evidenced by thermogravimetric analysis. This improvement of the thermal stability was also observed for the condensation products of the ortho and para isomers 6 and 7 with phenol and formaldehyde, leading to modified novolacs F? PP, although the amount of incorporated 6 and 7 was found to be less than the original amount in the reaction mixture.     

Etude de nouvelles membranes asymétriques à base de copolymère à blocs styrène-isoprène-styrène, 1. Synthèse,modification chimique et caractérisation

A styrene-isoprene-styrene block copolymer was selected for the preparation of new asymmetric membranes which have blood compatibility properties after chemical modification by addition of gazeous N-chlorosulfonyl isocyanate to the double bonds of the polyisoprene sequences. The membranes were examined with a scanning electron microscope. The permeability of the membrane was studied as a function of time, pressure and viscosity.     

Synthèse et caractérisation de quelques poly-ε-caprolactones

The presence of a certain degree of crystallinity in poly(1.2-dichloroalkamer)s, obtained by addition chlorination of a homologous series of stereoregular polyalkenamers, ranging from polybutenamer to polydodecenamer, may suggest a chain mechanism for chlorine addition. Three different approaches have been used in order to support such a mechanism by experimental evidences: Determination of the relative velocities of chlorine addition to the two double bonds of different dienes, used as model compounds of polyalkenamers. Investigation of the demolition products of partially chlorinated polyalkenamers. Examination of the DTA thermograms of partially chlorinated polyalkenamers.     

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.     

Synthèse, étude physicochimique et diélectrique de poly(acétoxyméthylstyrène)s

Various poly(acetoxymethylstyrene)s were synthesized. Examination of the physicochemical properties of the polymers as a function of the type of substitution revealed the influence of the position of polar groups on the thermal (glass transition temperature) and electrical (dielectric constant and loss factor) characteristics of the polymers. Because of their good solubility and their electrical properties over a wide range of temperatures and frequencies the polymers proved to be interesting materials for dielectric films.     

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 et caractérisation d'un amorceur azoïque disulfonique. Application à la polymérisation de l'acide acrylique

The synthesis of a water-soluble azo initiator was performed in four steps: action of hydrazinium sulfate onto 4-phenylbutan-2-one followed by an addition of hydrogen cyanide onto the azine, then oxydation with bromine and finally chlorosulfonation of the obtained aromatic azo compound. The overall yield of this azo compound was about 40%. The kinetical and thermal parameters were determined by differential scanning calorimetry. The decomposition rate constant (k_d) is similar to that of 2,2′-azoisobutyronitrile (AIBN) but the activation energy (ca. 38 kJ/mol) is lower than that of AIBN. The polymerization with this initiator in aqueous medium has advantages as compared with Fenton's reagent.     

Synthèse et caractérisation de copolymères coordinés par des sels métalliques

The anionic block copolymerisation of isoprene and 2-vinylpyridine (2VP) followed by a coordination with iron (III) chloride, leads to thermoreversibly crosslinked copolymers. These copolymers are character+ed by a low polydispersity (M?_w/M?_w≈1,1) between the coordination nodules of poly(2-vinylpyridine). The study of the swelling ratio at the equilibrium in benzene shows that such a polymeric network does not reach the equilibrium state expected from the thermodynamic analysis of the system. The presence of 2VP in the copolymer induces a screening effect which prevents the solvent diffusion through the polyisoprene network.     

Télomères monofonctionnels du chlorure de vinyle, 4. Synthèse et caractérisation par catalyse rédox

Monofunctional telomers of vinyl chloride ( 1 ) were synthesized by two ways. In the first one, the telomers resulting from the reaction of 1 with carbon tetrachloride were used as telogenic agents to react with allyl acetate leading to a monoadduct. In the second one, monofunctional telogens were used in a redox catalyzed reaction with 1 . Trichloroacetic acid and its esters ( 2b–d ) were applied as telogens. The theoretical maximum yields and the number average degrees of polymerization at these yields were calculated and compared with the experimental results.     

Synthèse et propriétés du poly(p-triméthylsilystyrène)

p-Trimethylsilylstyrene was found to be polymerisable anionically. When the reaction is carried out at low temperature in THF as solvent the polymer—poly(p-trimethylsilylstyrene)—is obtained in a quantitative yield and exhibits a low polydispersity. The glass transition temperature, viscosity-molecular weight relationships, and ¹H and ¹³C NMR spectra were investigated in order to compare the influence of the trimethylsilyl group located at the benzene nucleus with respect to polystyrene and some other p-subtituted polystyrenes. The presence of the trimethylsilyl group in para position of the aromatic nucleus results in an increase of the rigidity of the polymer chain and in an increase of the glass transition temperature.     

Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 14. Synthèse de copolymères butadiène-vinylferrocène

Hydrogen peroxide, thermally cleaved into hydroxyl radicals, was used as initiator of butadiene-vinylferrocene copolymerization. The influence of different parameters like temperature, pressure, proportion of hydrogen peroxyde and addition of a solvent with weak transfer capability was studied.