Uneven distribution of nanoparticles in immiscible fluids: Morphology development in polymer blends

AbstractThe present review aims at summarizing the current knowledge on how solid nanoparticles organize in polymer blends. First, the behavior of low viscosity fluid emulsions containing solid colloidal particles is briefly presented. By contrast with polymer blends, they have been the subject of intensive studies for a long time, with both applicative and comprehensive objectives. High viscosity fluid emulsions like polymer blends loaded with nanofillers have received less attention until the recent enthusiasm about nanotechnology and more specifically polymer nanocomposites. Some similarities and differences between both types of emulsions are highlighted. The solid particles are well known to distribute unevenly in those types of complex fluids and the factors that determine their distribution in polymer blends are discussed. A particular emphasis is given on the competition between thermodynamic wetting of the solid by the polymeric phases and kinetic control of the filler localization directly linked to the rate of the mixing process. This aspect is believed to be a specificity of filled polymer blends and is known to have a drastic and sometimes predominant effect on particle localization. It explains that finely tuned morphologies can be obtained where the particles do not occupy their equilibrium position

Rhéocinétique lors de la polymérisation avec séparation de phase dans un système thermoplastique/thermodurcissable.

4 p.Pour les matériaux polymères, la combinaison de l'écoulement et de la réaction chimique dans un outillage de transformation permet de générer in situ des structures ou des morphologies particulières à l'origine de nouvelles propriétés. Le contrôle du procédé requiert alors la connaissance de l'évolution de la rhéologie du système pendant la réaction chimique (rhéocinétique). Le travail exposé s'attache à décrire l'évolution des modules dynamiques d'un système complexe thermoplastique/thermodurcissable (polystyrène/époxy-amine) lors de la polymérisation du thermodurcissable. Les précurseurs du réseau sont initialement miscibles à haute température mais une séparation de phase sous forme de nodules sphériques intervient en cours de polymérisation. Des mesures microcalorimétriques de l'évolution de la transition vitreuse du thermoplastique et des observations en microscopie de la séparation de phase ont été réalisées. L'évolution des modules du système complexe au cours du temps a été suivie en rhéométrie dynamique. Sur cette base expérimentale, un modèle rhéocinétique prédictif des modules de perte et de conservation a été développé. Il intègre les phénomènes de séparation de phase, de variation de la température de transition vitreuse, de dilution des enchevêtrements de la phase TP dans le cadre d'un modèle d'émulsion généralisé à partir des modules dynamiques du TP et du TD en cours de polymérisation. La généralisation du modèle d'émulsion est réalisée en prenant en compte les interactions entre les particules de phase dispersée au delà du seuil de percolation mécanique sous la forme d'une loi de mélange

Synthesis of branched poly(butylene succinate): Structure properties relationship

International audience; A series of branched poly(butylene succinate) (PBS) were synthesized with several branching agents namely trimethylol propane (TMP), malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure of the branched polymers was analyzed by SEC and H-1-NMR. The effect of branching agent structure on crystallization was also investigated and played a significant role. Isothermal studies showed that glycerol propoxylate could act as a nucleating agent. By contrast high content of TMP disturbed the regularity of the chain and hindered the crystallization of PBS. From the non-isothermal kinetic study, it was found that glycerol propoxylate increased noticeably the crystallization rate due to the flexible structure of the branching agent. A secondary nucleation was observed with glycerol propoxylate attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. Chain topology was obtained through rheological investigations and the synthesized polymers showed a typical behavior of a mixture of linear and randomly branched PBS. The incorporation of branches improved the processability of PBS for film blowing application and the modulus and the stress at break of the resulting film were significantly increased

История развития математических знаний

Isosorbide is a platform chemical of considerable importance for the future replacement of fossil resource-based products. Applications as monomers and building blocks for new polymers and functional materials, new organic solvents, for medical and pharmaceutical applications, and even as fuels or fuel additives are conceivable. The conversion of isosorbide to valuable derivatives by functionalization or substitution of the hydroxyl groups is difficult because of the different configurations of the 2- and 5-positions and the resulting different reactivity and steric hindrance of the two hydroxyl groups. Although a substantial amount of work has been published using exclusively the endo or exo derivatives isomannide and isoidide, respectively, as starting material, a considerable effort is still necessary to transfer and adapt these methods for the efficient conversion of isosorbide. This Minireview deals with all aspects of isosorbide chemistry, which includes its production by catalytic processes, special properties, and chemical transformations for its utilization in biogenic polymers and other applications of interest

One-Pot Preparation of Dimethyl Isosorbide from d-Sorbitol via Dimethyl Carbonate Chemistry

Direct synthesis of dimethyl isosorbide (DMI) from d-sorbitol via dimethyl carbonate (DMC) chemistry is herein first reported. High yield of DMI was achieved using the nitrogen superbase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst and performing the reaction in a stainless steel autoclave by increasing the temperature from 90 to 200°C. In this procedure, DMC features its full capacity acting in the different steps of the process as carboxymethylating, leaving-group (cyclization), and methylating agent; DMC is also employed as the reaction media