Tensions superficielles de copolymères méthacryliques perfluoroalkylés

The surface properties of methacrylic copolymers with a random distribution of perfluoroalkyl pendent groups were studied by a tensiometric method and were found to depend on the concentration of fluorinated units (2-hydroxy-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononyl methacrylate ( 1 )), and the nature of the non-fluorinated methacrylic ester (methyl, butyl, stearyl). The surface tensions estimated by various approaches (critical surface tension, geometric and harmonic mean approximations) are very low (11 mN · m^?1 < y < 12 mN · m^?1). The surface tension of the copolymers drops drastically when a few percent of fluorinated units are incorporated into the polymeric chain. The wetting hysteresis, observed particularly in the case of water, could be due to the mobility of macromolecular chains at the interface, leading to a reorganization of fluorinated groups in order to minimize the interfacial energy.     

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.     

Synthèse et transformations chimiques des télomères de l'undécène-10 oate de méthyle, 2. Synthèse de diols polyhalogénés

Several telomers of methyl 10-undecenoate were prepared with different telogens and identified by IR and NMR spectroscopy or by GPC. Chemical transformations of these telomers led to new polyhalogenated acids of alcohols having high molecular weights.     

Synthèse de compoisés photoréticulables, 4. Estérification de l'acide acrylique sur les télomères de l'acrylate d'hydroxy-2 éthyle

Several telomers were prepared by redox catalysis from 2-hydroxyethyl acrylate ( 1 ) and telogens such as carbon tetrachloride, methyl trichloroacetate, 1, 1, 1-trichlorotrifluoroethane, and 2,4,4,4-tetrachloro-2-methylbutyric acid ( 2d ), as well as block-cotelomers from 1 and a telomer 4 prepared from chlorotrifluoroethylene and carbon tetrachloride. Polyols ( 3a–d and 5 ) with two to twenty primary hydroxyl groups were obtained. They were esterified with acrylic acid, to obtain new photosensitive compositions. ( 6a–d ).     

Polymères photoréticulables à unités cinnamiques, 1 Synthèse des monomères et polymérisation

The synthesis of cinnamic acid derivatives with a carbon-carbon double bond in para position was studied by a Knoevenagel reaction with p-chloromethylstyrene. The latter was obtained via a several-step reaction from 2-phenylethanol. The monomers can be polymerized by a free-radical process without affecting the cinnamic group. Copolymerization is effective only with monomers such as maleic anhydride, p-vinylbenzaldehyde or methyl methacrylate, having a π-acid character like the cinnamic acid derivatives used in our study.     

Modification des polyméres de vinyl-4 benzophénones méthoxylées et copolymérisation des monomères avec le styréne

The polymerization of acrylonitrile, methyl methacrylate and styrene initiated by copper(II) chelates was studied in the prescence of carbon tetrachloride. A polymeric amine and a monomeric diamine, that is, polyvinylamine and 1,3-diaminopropane, were chosen as ligands. The activity of the polymeric chelate was found to be specific and higher than that of the 1,3-diaminopropane chelate. It was compared with that of the 1,3-diaminopropane chelate, by changing pH values of the system and the reaction temperature. Plots of conversion against pH afforded a peak at pH 8, and trends of increasing of conversion were observed above pH 10. The apparent activation energy of the polymerization initiated by the polymeric chelate was higher than the apparent activation energy of the polymerization initiated by the 1,3-diaminopropane chelate. The fact was attributed to the difference of their chemical structures.     

Etude diélectrique de deux copolymères du méthylcyanure de vinylidène avec le 4‐fluorostyrène et le 4‐chlorostyrène

The dielectric properties of 2 copolymers poly[(methyl vinylidene cyanide)‐co‐(4‐chlorostyrene)] and poly[(methyl vinylidene)‐co‐(4‐fluorostyrene)] have been studied. These products are chiefly alternating and have relatively high glass transition temperatures, respectively at 145°C and 160°C. α relaxation phenomena have been characterised around to these temperatures. The values of dielectrical increment Δε have been calculated and compared to those of similar copolymers synthesized from vinylidene cyanide with various substituted styrenes. The low values are due to the steric effect of the bulky aromatic cycles. The orientation abilities of CN dipoles decrease comparatively to that of the copolymer of vinylidene cyanide with vinylacetate and this could explain the low piezo or pyroelectric properties.     

Effet de la concentration sur la transition conformationnelle des copolymères séquencés et greffés

In this paper we have been studying the effect of concentration c on reduced viscosity η_sp/c for a triblock copolymer poly(methyl methacrylate)/polystyrene/poly(methyl methacrylate) and for a graft copolymer of the same nature. The temperature of the experiments has been chosen in the range where the conformation changes from a segregated form to a pseudogaussian one. For this temperature range η_sp/c is not a linear function of concentration but the points η_sp/c vs. c are situated on two straight line segments with a well defined intercept. We discuss the phenomenon in comparison to results obtained on mixtures of homopolymers. These results suggest a strong and anomalous dependance of molecular conformation on concentration.     

Polymérisation de monomères carbonates de vinyle

Free-radical polymerizations of several aliphatic and aromatic N-substituted vinyl carbonates are described. The bulk polymerization was initiated at 35°C with di-tert-butylcylohexyl peroxydicarbonate yielding high-molecular-weight poly(vinyl carbonate)s. The structure of these polymers was examined by FTIR spectroscopy and the molecular weight by GPC. The effects of the substituents on the physical properties of the resulting polymers were studied. A comparison of the properties with those of similar compounds described in the literature was made.     

Influence du degré de ramification sur la température «theta» de quelques polymères dans différents solvants

The lowering of the Θ-temperature observed for branched polystyrenes in cyclohexane is extended to other systems: polystyrene in diethyl malonate, in decaline and in a mixed solvent (78% benzene/22% methanol), and to some other polymers such as polyisoprene in methyl propyl ketone and poly(vinyl acetate) in 3-heptanone and ethanol. The temperature Θ (measured by light scattering), and the precipitation temperature T_p (measured by liquid-phase separation) of these polymers are always lower than for linear polymers of the same chemical nature. The Θ-temperature decreases with increasing degree of branching.     

Polymères thiocarboxyliques, 2. Synthèse par modification de polymères préformés

Dithioester groups were introduced into linear or crosslinked polystyrenes by Friedel-Crafts reaction with ClCH₂Si(CH₃)₃/CS₂ or with ethyl chlorodithioformate, as well as thioamide groups by reaction with ethoxycarbonyl isothiocyanate. Treatment of several copolymers of acrylonitrile with ethanethiol and hydrogen chloride and subsequently with H₂S led to copolymers with dithioester and thioamide groups in the side chains without cyclization. Most of these reactions occur without crosslinking.     

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.     

Terpolymérisation acrylonitrile-styène-acrylate de méthyle, 2. Synthèse de terpolymères homogènes en composition par polymérisation en émulsion

Previous Kinetic studies of the emulsion polymerisation of the three component system acrylonitrile (A) — styrene (S) — methyl acrylate (M) have shown that S is much more reactive than A and M, which have practically the same reactivities. As a consequence, in batch process a large copolymer composition drift is observed versus conversion. To avoid this damageable drift, two techniques were investigated, to get homogeneous macromolecules. (1) Application of the well known “semi-continuous technique” which appeared not to be totally satisfactory, since the initial batch polymer fraction generally has a composition different from the further polymer when the monomer feed is added under starving conditions; a mixture of various macromolecules is the result. (2) The use of the composition controlled reactor, developed in this laboratory, which consists in a continuous monitored readjustment of monomer feed composition. However, due to the heterogeneous medium of an emulsion copolymerization, the copolymer exerts a small chemical heterogeneity which may be practically negligible at high monomer/water ratio. It is finally proposed that a thermodynamic approach might overcome such a behaviour and insure an actual control of the copolymer composition.     

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.     

Synthèse de polymères étoiles par réaction de polymères ω-fonctionnels sur des polyisocyanates

The present investigation was undertaken to study further the synthesis of networks with viscoelastic properties. This involves two stages: synthesis of functional polymers with reactive chain ends and selective condensation reaction with polyfunctional crosslinking agents. In order to determine the conditions of crosslinking reaction, a preliminary study was realised on the branched star polymer synthesis. These polymers are obtained by reaction of ω-functional polymer with tri-, tetra-, and pentaisocyanates. Polymers used in this work were polyisoprene, polybutadiene, polystyrene, block copolymers from diene and styrene with hydroxylic end groups. The reaction of the liquid polymer having hydroxylic end groups with isocyanates leads to a branched star polymer with formation of an urethane group, the average branching depending on the functionality of the polyisocyanates. Structures of this star polymer are confirmed by NMR analysis and by determination of the rel. mol. mass.     

Perméabilité des matériaux copolymères: modélisation moléculaire, 1. Essai d'application d'un modèle de percolation

The diffusion of small molecules across a copolymer membrane is simulated as a site percolation problem, assuming that in copolymers consisting of A and B units, B are active sites and A are inactive sites. Molecular modeling is conducted in three steps: (i) generation of a copolymer by a Monte-Carlo process, taking into account the sequence distribution of the copolymer, (ii) organization of the material through a slipping process of the linear chain towards maximization of the dipolar interactions between the A units, and (iii) the site percolation itself. A quantitative application is carried out for acrylonitrile/methyl acrylate copolymers. The results show that the influence of the slipping process upon the internal organization of the material is most important.     

Recherche de télomères à activité pharmacologique potentielle, 2. Télomères de l'acide acrylique et greffage de composés hydroxylés

Several telomers of acrylic acid with carbone tetrachloride were prepared. Their average degree of polymerization, which was between 10 and 50, was determined by several analytical methods (elemental analysis, viscosimetry, and GPC). From the kinetic equations of telomerization a relation between DP _n of these telomers and the experimental conditions is established. Fixation of hydroxylic compounds through direct esterification was studied and it was found that the prepared telomers can be used as hydrosoluble carriers for drugs containing primary alcohol or phenol functions.     

Synthèse de polymères ω-hydroperoxyde

The general conditions are described for the synthesis of ω-hydroperoxy polymers by reaction of oxygen with C? Li bonds of anionic living polymers. Secondary reactions as interchain coupling and the formation of alcohols are also discussed. In order to obtain a quantitative hydroperoxydation the following experimental parameters must be observed: (a) slow addition of the living solution to a polar solvent saturated by oxygen; (b) low concentration of living ends; (c) bulky terminal units; (d) lowest possible temperature.     

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 par voie radicalaire de polymères à extrémités hydroxylées, 5. Polymérisation du méthacrylate de méthyle sous rayonnement ultraviolet

Hydrogen peroxide is cleaved by UV irradiation (253,7 nm) into two hydroxyl radicals which can be used as initiators of polymerization, in order to give hydroxytelechelic polymers. Yields and number average molecular weights are influenced by the presence of an alcohol in the reaction medium, and the results depend on the solubility of the polymer in the alcohol used. The polymerisation of methyl methacrylate in methanol, being a non-solvent for the polymer, is described in the present paper. The characteristics of the polymers obtained are studied: distribution of molecular weights, microstructures, proportion of hydroxyl groups per macromolecule; the influence of several parameters—reaction time, proportion of hydrogen peroxide, and nature of the reaction medium—is also studied.