Cristallisation de poly(oxyéthylène)s segmentés

Two homologous series of segmented poly(oxyethylene)s, comprising from 1 to 4 blocks, were studied by differential scanning calorimetry, dilatometry and low-angle X-ray scattering. The polymers used were synthesized by condensation of α,ω-dihydroxy poly(oxyethylene)s with molecular weights of 2750 and 10600, respectively, upon 2,4-toluene diisocyanate. It was shown that the structure of these polymers is lamellar as for the usual poly(oxyethylene)s, but the degree of crystallinity and the melting temperature decrease appreciably with increasing degree of condensation. The thickness of the lamellae of the two-block polymers increases drastically and stepwise with crystallization temperature, exactly as in the case of weakly polydisperse, ordinary poly(oxyethylene)s. On the other hand, the thickness of the lamellae is little affected by the crystallization temperature for tri- and tetra-block polymers. The conclusion is drawn that this is due to a blocking of the urethane groups during the annealing process. As these groups are excluded from the crystalline domains, they play the same rǒle as end groups of the chains in ordinary poly(oxyethylene)s.     

Cristallisation du poly(oxyéthylène) dans des copolymères biséquencés, 1. Étude dilatométrique

The crystallization from the melt and the annealing process of poly(oxyethylene) blocks were studied by dilatometry for a series of poly(ethyl methacrylate)/poly(oxyethylene) and polystyrene/poly(oxyethylene) two-block copolymers. The degrees of crystallinity which can be attained are very high. The partial specific volume of each block was calculated and the melting process of the crystalline sequences was examined.     

Synthèse et caractérisation de copolymères séquencés poly(méthacrylate d'alkyle)/poly(oxyéthylène)

Poly(alkyl methacrylate)/poly(oxyethylene) block copolymers were synthesized by anionic polymerization in tetrahydrofurane in vacuum with diphenylmethylpotassium as initiator. In the case of poly(ethyl methacrylate)/poly(oxyethylene) copolymers, samples were fractionated from benzene solution by progressive addition of 2,2,4-trimethylpentane. Nuclear magnetic resonance and lightscattering were used to characterize the fractions. It was shown that copolymers thus prepared are free from homopolymers, and that the polydispersity in weight and composition is small.     

Cristallisation du poly(oxyéthylène) dans des copolymères séquencés, 2. Étude de la structure et de la texture

The lamellar structure of a series of two-block poly(oxyethylene)/poly(ethyl methacrylate) and poly(oxyethylene)/polystyrene copolymers was studied by low-angle X-ray diffraction, as a function of the temperatures of crystallization and annealing. The thickness of the lamellae increases with temperature; the number of folds of the crystalline polymer chains varies, apparently, in a continuous way. The discontinuous increase of the thickness observed at 40°C in the annealing experiments was interpreted in terms of the glass transition temperature of the amorphous blocks. The spherulithic texture of the samples was examined by microscopy with polarized light.     

Polymères thiocarboxyliques, 5. Synthèse de poly(oxyéthylène)s à fonction dithioester terminale. Application au traitement de cellules d'électrophorèse

Poly(oxyethylene)s with dithioster end groups were obtained from mono- and dihydroxyl terminated commercial polymers by reaction with dimethyl chloroacetamide, subsequent thionation of the amide group, and usual conversion of the thioamides into the dithioesters 14, 15 and 20, 21 . The best results were obtained in the syntheses of the S-carboxymethyl dithioesters ( 15 and 21 ). The resulting reactive poly(oxyethylene)s were grafted upon silica tubes and electrophoresis cells, previously activated by aminopropylsilanization. These graftings result in lowering of the surface potential of the tubes and in suppression of the electro-osmosis flow in an electrophoresis cell tested with a TiO₂ standard sample.     

Amorceurs radicalaires fonctionnels, 2. Macroinitiateurs à partir de l'α-hydrogeno-ω-hydroxypoly(oxyéthylène) et des acides tert-butyldioxycarbonylbenzoïques

Modified polystyrenes were obtained by free radical polymerization of styrene using the macroinitiators α-tert-butyldioxyterephthaloyl(or phthaloyl)-ωtert-butyldioxyterephthaloyl(or phthaloyl)poly(oxyethylene) ( 3 and 4 ), which were synthetized. To examine the stability of such compounds, thermolysis kinetics of model compounds, OO-tert-butyl O-methyl monoperoxyphthalate ( 6 ) and terephthalate ( 7 ) were studied by differential scanning enthalpimetry. Suspension polymerization of styrene applying the industrial method, showed that the macroinitiator is able to initiate the process. A polystyrene containing up to 4% by weight oxyethylene units was obtained.     

Autoxydation radio-induite du poly(oxyéthylène) en solution aqueuse, 7. Cinétique de la consommation d'oxygène

The rate of oxygen consumption, the formation of oxidation products, and chain scissions were determined during the autoxidation of poly(oxyethylene) in aqueous solution at 25°C by initiation with γ-rays. Oxidation products account for the quasi-totality of the oxygen consumption observed. There are two processes by which equivalent amounts of oxygen are consumed, hydroperoxidation and oxidative degradation.     

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 et caractérisation de copolymères séquencés poly(vinyl-2 pyridine)/poly(oxyéthylène)

Hydrophobic-hydrophilic poly(2-vinlypyridine)/poly(ethylene oxide) block copolymers were synthesized by anionic polymerization in tetrahydrofuran in vacuum with diphenylmethylpotassium as initiator. The resulting polymers were fractionated from benzene solution by progressive precipitation with 2,2,4-trimethylpentane at 35°C. Gel permeation chromatography, light scattering, osmometry, and ¹H NMR were used to characterize the fractions. The copolymers, thus prepared, were found to have a well defined structure and a low polydispersity in both molecular weight and chemical composition.     

Compatibilité de polymères porteurs de groupements amides tertiaires avec le poly(difluoro-1,1 éthylène). Etude par enthalpimétrie différentielle

The miscibility of poly(1,1-difluoroethylene) ( 1 ) with poly(N-vinyl-2-pyrrolidone) poly(N-methyl-N-vinylacetamide) and poly(N,N-dimethylacrylamide), containing tert-amido groups, was investigated by differential scanning calorimetry. Amorphous homogeneous blends were obtained whenever the weight fractions of polymer 1 is less than 0,7. The dependence of the single glass transition temperature (T_g) versus composition may be readily analyzed either through the Gordon-Taylor equation (high values of the k parameter, suggesting strong specific interactions between the homopolymers) or by means of the Couchman relation (no adjustable parameter). The broadening of the glass transition range and the variation of the increment of specific heat at T_g for the blends are discussed.     

Synthèse de diamines aromatiques macromoléculaires à basicité controlée à partir de poly(tétraméthylène glycol)

This study describes the synthesis of poly(tetramethylene glycol) with amino end-groups on both sides by chemical end modification. For this purpose, α-hydro-ω-hydroxypoly(oxytetramethylene) and α-propyl-ω-(3-aminopropoxy)poly(oxytetramethylene) are converted into aromatic diamines with controlled basicity. For this, different chemical reactions are performed in order to obtain different links between aromatic amines and poly(oxytetramethylene). This method leads to products which present pK_a values between 2,8 and 5,26 in accordance with theoretical values.     

Synthesis and permeation behavior of membranes from segmented multiblock copolymers containing poly(ethylene oxide) and poly(β-benzyl L-aspartate) blocks

Novel segmented multiblock copolymers ( 7 ) were synthesized by linking poly(ethylene oxide) (PEO) blocks with poly(β-benzyl L -aspartate)(PBLA) blocks via urethane and urea bonds, which were formed by the reaction of 4,4′-methylenediphenyl isocyanate ( 5 ) with the terminal hydroxyl groups of α-hydro-ω-hydroxypoly(oxyethylene) ( 4 ) and the terminal amino groups of poly(β-benzyl L -aspartate)-block-iminohexamethyleneimino-block-poly(β-benzyl L -aspartate) ( 3 ) [prepared from 1,6-hexanediamine ( 1 ) and β-benzyl L -aspartate N-carboxy anhydride ( 2 )], respectively. Membranes with various water contents were obtained from these copolymers by changing the lengths of the PEO and PBLA segments. The study of the permeation of 1-phenyl-1,2-ethanediol, vitamin B₁₂ and myoglobin through the membranes showed a high dependency of the permeability on the molecular weight of the solutes.     

Réactions primaires de dégradation oxydante au cours de l'autoxydation du poly(oxytétraméthylène) à 25°C, 1. Caractérisation de la production d'éthylène

Autoxidation of poly(oxytetramethylene) at 25°C was studied by means of radiation induced initiation of chloroformic solutions of the polymer. It includes primary oxidative degradation reactions characterized by main chain scissions and subsequent formation of ethylene, formate groups, and hemiformal groups.     

Etude de la polycondensation linéaire de polymères précurseurs α,ω-bifonctionnels avec des agents de couplage bifonctionnels de faible masse molaire

Chain extension reactions involving α,β-bifunctional precursor polymers and bifunctional coupling agents of low molecular weight were investigated both theoretically and experimentally. The number and weight molecular weight distributions were calculated, and computer simulations were performed, neglecting the weight of the coupling agent with respect to that of the precursor polymer. Examples of such chain extension reactions include the polycondensation of “living” α,β-dicarbanionic polystyrene with 1,4-bis(bromomethyl)benzene, and the reaction of poly(oxyethylene)glycol with a low-molecular-weight diisocyanate. The characterization of the resulting polymers yields results that are in satisfactory agreement with the theoretical expectation.     

Les effets thermiques associés à la transition vetreuse de films de poly(téearéphatalate d'éthylène)

Differential scanning calorimetry and thermomechanical analysis are used for examining the thermal behaviour of amorphous poly(ethylene terephthalate) films in the glass-transition range. By variation of the heating rate between 0,2 and 100 K. · min^?1, it is possible to obtain either an exotherm associated with a shrinkage, or an endotherm, or both of these phenomena. It is found that very low heating rates not only give rise to a retardation mechanism but also to a molecular rearrangement.     

Comportement de copolymères greffés en milieu solvant sélectif des greffons. Cas des copolymères poly(styrène-g-bromure de vinyl-4 N-éthylpyridinium)

The dilute solution properties of amphiphilic graft copolymers with an “insoluble” polystyrene backbone (PS) bearing “soluble” poly(4-vinyl N-ethylpyridinium bromide) grafts (PVPQ), were studied in water-methanol-LiBr (0,1 mol/l) mixtures. In contrast to block copolymers with an identical chemical nature and in the same solvents, graft copolymers do not present intermolecular association. Viscometric data clearly show that a single graft molecule (or “monomolecular pseudo-micelle”), has a structure similar to that of a “plurimolecular micelle” of a block copolymer, and exhibits a compact star-like structure.     

Photodégradabilité de copolymères styrèniques comportant des motifs de chaîne α-phényl et β-phénylcétone. Polycétones issues de I'hydrolyse de polyméres et copolymères d'acétoxyphénylbutadiéne et de phényl(triméthylsiloxy)butadiènes

The present work reports on the photodegradation of macromolecules (poly(styrene-co-carbon oxide)) having α-phenyl and β-phenylcarbonyl groups along the main chain. The photochemical behavior of polyketones containing β-phenylcarbonyl groups and their comparison with the behaviour of a polyketone containing α-phenylcarbonyl are expected to give useful informations. With this purpose polyketones constituted of 3-oxo-1-phenylbutane-1,4-diyl units (i) regularly head-to-tail linked ( I ), (ii) included in polystyrene ( II ) or (iii) in poly(1-phenylbutadiene) ( III ) and polyketone constituted of 3-oxo-2-phenylbutane-1,4-diyl units ( IV ) have been considered. The synthesis of I by hydrolysis of polymers of 3-acetoxy-1-phenyl-1,3-butadiene ( 2a ) and of 1-phenyl-3-(trimethylsiloxy)-1,3-butadiene ( 2b ) have been tested: the polyketones I are proved to be more easily accessible from 2b and its polymer ( 3b ) than from 2a and its polymer ( 3a ). The polyketones II, III and IV have then been synthesized from the copolymer ( 4 ) of 2b with styrene, the copolymer ( 5 ) of 2b with 1-phenyl-1,3-butadiene, and the polymer ( 8 ) of 2-phenyl-3-(trimethylsiloxy)-1,3-butadiene ( 7 ), respectively. The photochemical behavior of these polyketones and copolyketones is in accordance with the previously observed regiospecific α-phenyl-side towards the β-phenyl-side fragmentation and shows that the expected photosensibilisation of the β-phenyl-side fragmentation by increasing phenyl to carbonyl ratio is not observed.     

Synthèse de polystyrènes chlorométhylés renfermant des radicaux tétrathiafulvalénylphénoxyméthyles

In order to study the influence of the nature of the moiety bearing a tetrathiafulvalenyl group in the polymers upon the microlithographic properties of resists, poly(p-chloromethylstyrene)s and poly(styrene-co-p-chloromethylstyrene)s containing the 4-tetrathiafulvalenylphenoxymethyl group with a variety of controlled molecular weights and molecular weight distributions were studied. The copolymers were all prepared by reaction of poly(4-vinylbenzyl chloride) with potassium 4-tetrathiafulvalenylphenolate ( 3 ). Without exception, the resulting poly[p-chloromethylstyrene-co-p-(tetrathiafulvalenylphenoxymethyl)styrene]s are highly insoluble. However, by reaction of potassium 4-tetrathiafulvalenylphenolate with poly(styrene-co-p-chloromethylstyrene) soluble copolymers could be prepared.     

Synthèse de polysiloxanes organofonctionnels, 1. Chloration des poly(diméthylsiloxane)s par le chlorure de sulfuryle

Sulfuryl chloride was used as chlorination agent of poly(dimethylsiloxane)s (1) in order to obtain poly(dimethylsiloxane-co-chloromethylmethylsiloxane) and it was found to be more specific than molecular chlorine. Identification of chlorinated and chlorosulfonated units was shown to be possible by comparison of the results of ¹H NMR spectroscopy with those obtained by GLC analysis of the mixtures obtained from octamethylcyclotetrasiloxane (2) . After having shown that the distribution of the various types of methyl groups in 1 and 2 , modified in this way, fits correctly a binomial law and that chlorosulfonated units can be hydrolysed, copolymers containing 20 to 25% of chloromethylated units and less than 2% of unwanted dichloromethylated units are accessible by use of this chlorination agent.     

Réactions primaires de dégradation oxydante au cours de l'autoxydation du poly(oxytétraméthylène) à 25°C, 2 Cinétique de la production d'éthylène

The kinetics of the production of ethylene during the radiation induced autoxidation of poly(oxytetramethylene) were determined in chloroform solution at 25°C. It was found that the primary oxidative degradation of the polymer generating ethylene is part of a chain reaction process.