Influence de la masse moléculaire,de la polydispersité et de la température sur les phénomènes de solvatation préférentielle de polystyrènes linéaires dans différents mélanges de solvant

This paper describes the study of preferential adsorption of polystyrene in a solvent mixture as a function of different parameters. In the first place the influence of the density of intramolecular segments (the effect of the molecular weight and the polydispersity of the polymer) on this phenomenon was examined. The effect of the temperature on the solvation coefficient was also considered. Certain experimental results were found to be in good agreement with the thermodynamic theories of preferential adsorption. The lack of the knowledge concerning the variation of the thermodynamic interaction parameters, with the density of intramolecular segments and the temperature, did not permit a rigorous quantitative study.     

Propriétés physicochimiques d'une série de polystyrènes deutériés en solution dans le tétrahydrofuranne

The physicochemical properties of a series of deuterated polystyrenes were investigated in tetrahydrofuran by viscosity, light scattering (LS), on line LS-GPC, and size exclusion chromatography (GPC). The viscosity laws and unperturbed dimensions of deuterated (PSD) and “hydrogenated” (PSH) polystyrene were compared. There are small but distinct differences in the solution behaviour of PSH and PSD. Some optical properties of partially D-labelled polystyrenes were investigated.     

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.     

Étude de la solvatation préférentielle des poly(méthacrylates de méthyle) dans quelques mélanges de solvants

The behavior of some poly(methyl methacrylate)s in solvent-mixtures (benzene-methanol, carbone tetrachloride-methanol and dioxane-methanol) was investigated. The dependence of microstructure and molecular weight of the polymer on the preferential solvation was determined. The existence of a conformational transition for syndiotactic poly(methyl methacrylate) in dioxane and in dioxane-methanol could be shown.     

Théorie des chaînes de Markov et distribution moléculaire dans les copolycondensats linéaires, 2. Systèmes d'ordre II

Application of a mathematical model — based jointly on Graph Theory and Markov chains theory — to the molecular distribution in monodimensional systems of order II (i.e. systems with functional groups belonging to two distinct co-reactive species A and B) allows one to obtain very general matrix expressions for the molecular distribution functions of many linear copolycondensates.     

Etude des solutions de polymères dans un mélange de solvants au voisonage de leur point critique de démixtion, 1. Système méthanol/cyclohexane/polyvinyl-2 pyridine

It is shown that small quantities of poly(2-vinylpyridine) extensively change the coexistence curves of the two liquids methanol/cyclohexane, especially in the vicinity of the critical point of the two liquids. It is possible to observe as a function of temperature two domains of solubility separated by three domains of precipitation when the polymer has a molecular weight 200 000. Moreover the dimensions of the dissolved poly(2-vinylpyridine) are abnormally high in the region of the critical point of the two liquids.     

Approche simple du problème de la distribution des séquences dans les terpolymères

This work deals with a very simple determination of the variation limits, and to some extent, to the variation itself of the sequence distribution in a terpolymer without assistance of computer programming. A simple analytical approach is stated and shown that it is sufficient to consider only the corresponding binary copolymerizations involved in the ternary polymerization. Calculations are applied to the function A_c/L?_n(A), i.e. the ratio of the mole fraction of monomer A in the terpolymer A_c to the number average sequence length of this monomer in the terpolymer.     

Théorie des chaînes de markov et distribution moléculaire dans les copolycondensats linéaires, 3. Systèmes à n états

By the application of Markov chains theory to stochastic graphs representing monodimensional macromolecular systems it is possible to study the molecular distribution of macromolecular systems. The use of matrix calculus leads to simple mathematical expressions for the different molecular distribution functions. These functions due to their generality can be applied to many different systems. They give in particular, the molecular distribution resulting from the coupling of linear primary polymers having themselves a given molecular distribution. Finally, in the mathematical model developed, it is possible to take into account the differences of reactivity between functional groups; thus, systems having intrinsically non-equireactive functional groups and systems where the non-equireactivity of the sites may be assigned to substitution effects can been studied with this model, the only consequence being an increase in the number of the possible states of the system.     

Structure lamellaire des copolymères séquencés: Paramètres structuraux et coefficient de partage du solvant dans le gonflement du copolymère biséquencé polystyrène/polyisoprène

The lamellar structure of a two-block polystyrene/polyisoprene copolymer was studied by small angle X-ray diffraction as a function of the solvent content of the samples. The analysis of the intensity of the diffraction lines has permitted the evaluation of the distribution coefficient of the solvent between the microdomains of segregation. The change of the structural parameters as a function of the affinity of each solvent with respect to both blocks was studied. It was shown that the swelling of the lamellar structure proceeds parallel to the interfaces of the lamellae when the solvent used does not preferentially dissolve one of the blocks, whereas it corresponds to an increase of the thickness of the lamellae if preferential solution of one of the blocks by the solvent takes place.     

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.     

Réticulation anionique du polystyrène en présence de chaînes polymériques libres

Semi-interpenetrating polymeric networks based on polystyrene were prepared by anionic polymerisation. Factors affecting synthesis, such as composition, molecular weight of either the unattached polystyrene or the polystyrene between crosslinks, have been varied. Their effect on network formation was examined by extraction experiments and swelling measurements.     

Etude du couplage chromatographie d'exclusion-diffusion de la lumière, 1. Dispositif expérimental et étude de polystyrènes «références»

The possibilities of coupling size exclusion chromatography with light scattering (GPC-DDL) are studied. The continuous light scattering detector is a modified (laser He-Ne excitation) classical light scattering apparatus Fica 42000, equipped with a flow cell of low capacity (120μl). With this cell, a detection of the scattered light is obtained only at an angle of 90°. The light scattering detector is coupled with a GPC apparatus (packed with 10 μm gel particles). The precision, reproducibility and limitation to obtain molecular weight distribution curves of “standard” linear polystyrenes are studied.     

Étude viscosimétrique du système ternaire polystyrène/poly(méthacrylate de méthyle)/p-xylène

Some theoretical considerations and experimental results are presented on the limiting viscosity number of polystyrene, (PS), dissolved in a mixture of poly(methyl methacrylate), (PMMA), and p-xylene, and of PMMA in a mixture of PS and p-xylene. At relatively low concentration, this problem can be treated using the classical formalism of dilute solutions, introducing in addition a new parameter b_AB characterizing the interactions between the polymers A and B. The quantitative use of this apparently simple method involves some difficulties owing to the fact that terms of higher order have to be taken into account even at moderate concentrations. The results can be explained by a decrease of the polymer dimensions which is more pronounced when the “solvent polymer” is of low molecular weight. At higher concentration, there is a critical point which seems to appear when the total volume of the two polymers is equal to the volume of the solution.     

Réctions de greffage sur des dérivés halogénés du polystyreègne. Préparation de polystyrènes en peigne

The polymerization of methyl methacrylate in the presence of ceric ion and pinacol in acetic acid solution has been investigated. Acetone formed in the reaction products has been determined and the mechanism and kinetics of the polymerization have been studied. It has been confirmed that the primary radical formed from pinacol reacts with not only the monomer to produce a monomer radical and initiate the polymerization but also with ceric ion. Under the present experimental conditions, the reaction of the primary radical with ceric ion is about 127 times as fast as that with monomer. The monomer radical produced reacts with another monomer to propagate polymerization. The polymerization is terminated by reaction of the polymer radical with ceric ion. The rate of polymerization was proportional to [pinacol], [monomer]² and reciprocal to [Ce^IV].     

Synthèse de polystyrènes chlorométhylés renfermant des radicaux tétrathiafulvalène carbonyloxyméthyles

In order to solve the problem of polymer swelling, which limits the resolution for negative resists, new resists were developed which show no swelling. The undesirable swelling can be suppressed by converting nonpolar crosslinked polymers into polar ones, which are soluble after irradiation. This aim was attained by mixing a polystyrene bearing tetrathiafulvalenyl (TTF) groups with 1,2-dibromo-1,1,2,2-tetrachloroethane. For our study, we applied resists including poly(4-chloromethylstyrene)s containing tetrathiafulvalenecarbonyloxymethyl groups ( 1 and 2 ). Poly(4-chloromethylstyrene)s ( 4 ) or poly[styrene-co-(4-chloromethyl)styrene]s ( 5 ) with a variety of controlled molecular weights and molecular weight distributions were prepared by radical chain polymerization. The reaction of cesium tetrathiafulvalenecarboxylate ( 3 ) with 4 or 5 was carried out and the resultant substituted polymers 1 and 2 were characterized.     

Synthèse de polyglutarimides à partir de PMMA,de la cyclohexylamine et de la méthylamine, 3 Etude du mécanisme d'imidification sur des modèles macromoléculaires

In order to check the mechanism of intramolecular cyclization to obtain glutarimide rings, we have prepared various homo and copolymers: homo N‐methyl‐ and homo N‐cyclohexylmethacrylamide and the corresponding copolymers with MMA and MAA. This first study showed that methacrylamides are less reactive than other methacrylic derivatives as shown by the r₁ and r₂ values of MMA and N‐cyclohexylmethacrylamide. The cyclization at 250°C in xylene proves that in the case of N‐cyclohexyl derivatives, the following reactivity is obtained: amide‐acid ≫ amide‐amide ≫ amide‐ester. On the contrary with N‐methyl derivatives, the reactivity of each complex is higher although amide‐acid remains the more reactive. The steric hindrance may account for this phenomenon.     

Etude d'un mutant modifiant le métabolisme du méthanol chez une souche de Pseudomonas

A glycine-resistant mutant was isolated from a methylotrophic strain of Pseudomonas species possessing serine pathway. This mutant presents some improvements in regard to growth parameters, and is able to excrete a fluorescent pigment under certain culture conditions. This pigment is capable of accelerating the reduction rate of formaldehyde to formate coupled with NAD. The same cannot be said for the wild type.     

Micellisation de copolymères séquencés polystyrène-polyvinylpyridinium, 2. Influence des caractéristiques moléculaires des copolymères

The influence of the molecular characteristics of polystyrene-poly(4-vinyl-N-ethylpyridinium bromide) block copolymers (PS-PVPQ) on their dilute solution properties is investigated in a solvent selective for polyelectrolytic moieties (water-methanol-0,1 mol/1 LiBr mixtures). It is shown that the association degree depends much more upon the length of the insoluble hydrophobic part of the macromolecule than on the length of the soluble hydrophilic part. Micelle dimensions could not be determined from light scattering measurements because of the compactness of the particles. Attempts for the calculation of micelle size were made using a star-like micellar model.