In Situ-Forming Oleogel Implant for Rivastigmine Delivery

International audienc

Hydrogen bonding and miscibility behavior in poly[ethylene-co(acrylic acid)] and poly(N-vinylpyrrolidone) mixtures

The miscibility behavior promoted by hydrogen bonding interactions in mixtures of poly(N-vinylpyrrolidone) (PNVP) and a copolymer of ethylene/acrylic acid (PEAA-20) is studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and infrared spectroscopy. Mixtures become immiscible when hydrogen-bonding interactions weaken. DMTA and dielectric relaxation spectroscopy reveal a sub-vitreous transition in the PVNP at about 52�C. This transition superimposes with the glass transition of PNVP-rich blends. � Wiley-VCH Verlag GmbH, 2001

Hydrogen bonding and miscibility behavior in poly[ethylene-co(acrylic acid)] and poly(N-vinylpyrrolidone) mixtures

The miscibility behavior promoted by hydrogen bonding interactions in mixtures of poly(N-vinylpyrrolidone) (PNVP) and a copolymer of ethylene/acrylic acid (PEAA-20) is studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and infrared spectroscopy. Mixtures become immiscible when hydrogen-bonding interactions weaken. DMTA and dielectric relaxation spectroscopy reveal a sub-vitreous transition in the PVNP at about 52°C. This transition superimposes with the glass transition of PNVP-rich blends. © Wiley-VCH Verlag GmbH, 2001

Effect of the acrylic acid content on miscibility and mechanical properties of mixtures of poly[ethylene-co-(acrylic acid)] and poly(2-ethyl-2-oxazoline)

The miscibility behavior of blends of poly(2-ethyl-2-oxazoline) (PEOX) and poly[ethylene-co-(acrylic acid)] was studies as a function of the acrylic acid content with the help of differential scanning calorimetry (DSC), modulated DSC and dynamic mechanical thermal analysis (DMTA). Miscibility, ascertained by the existence of a single glass transition in the mixtures, is achieved only between the PEOX and the copolymers with a high acrytic acid content (20%). The other two polymer pairs are immiscible at all compositions. FTIR spectroscopy demonstrates that miscibility is enhanced by hydrogen bonding interactions between the amide groups of the PEOX and the carboxylic groups of the acrylic acid units in the copolymer. Tensile stress and compressive creep tests reveal that the 20 and the 40 wt.-% PEOX blends exhibit synergistic mechanical properties, i.e., better ultimate properties, smaller Young's moduli and higher creep compliances. � Wiley-VCH Verlag GmbH, 2001

Effect of the acrylic acid content on miscibility and mechanical properties of mixtures of poly[ethylene-co-(acrylic acid)] and poly(2-ethyl-2-oxazoline)

The miscibility behavior of blends of poly(2-ethyl-2-oxazoline) (PEOX) and poly[ethylene-co-(acrylic acid)] was studies as a function of the acrylic acid content with the help of differential scanning calorimetry (DSC), modulated DSC and dynamic mechanical thermal analysis (DMTA). Miscibility, ascertained by the existence of a single glass transition in the mixtures, is achieved only between the PEOX and the copolymers with a high acrytic acid content (20%). The other two polymer pairs are immiscible at all compositions. FTIR spectroscopy demonstrates that miscibility is enhanced by hydrogen bonding interactions between the amide groups of the PEOX and the carboxylic groups of the acrylic acid units in the copolymer. Tensile stress and compressive creep tests reveal that the 20 and the 40 wt.-% PEOX blends exhibit synergistic mechanical properties, i.e., better ultimate properties, smaller Young's moduli and higher creep compliances. © Wiley-VCH Verlag GmbH, 2001

Electron and light microscopy studies on the domain structures of Zn 3B7O13Cl, Zn3B7O 13Br and Zn3B7O13I ferroic boracites

Poly(styrene-co-sodium acrylate) has been synthesized by emulsion polymerization of styrene and sodium acrylate at a ratio of 9:1 with the water-soluble initiator potassium persulfate. The reaction is fast, conversions are high, and the evolution of particle size follows the conversion curve. The final latex is stable and contains spherical particles 70 nm in diameter. The presence of the copolymer is confirmed by several methods including FTIR, and the copolymer evolves from rich in sodium acrylate to rich in styrene as the reaction proceeds. " 1993 Springer-Verlag.",,,,,,"10.1007/BF00296851",,,"http://hdl.handle.net/20.500.12104/41219","http://www.scopus.com/inward/record.url?eid=2-s2.0-0001123646&partnerID=40&md5=3def5991a6590b5c5368988837197fc2",,,,,,"2",,"Polymer Bulletin",,"20

Emulsion copolymerization of styrene and sodium acrylate

Poly(styrene-co-sodium acrylate) has been synthesized by emulsion polymerization of styrene and sodium acrylate at a ratio of 9:1 with the water-soluble initiator potassium persulfate. The reaction is fast, conversions are high, and the evolution of particle size follows the conversion curve. The final latex is stable and contains spherical particles 70 nm in diameter. The presence of the copolymer is confirmed by several methods including FTIR, and the copolymer evolves from rich in sodium acrylate to rich in styrene as the reaction proceeds. © 1993 Springer-Verlag

Polymer nanocomposites containing carbon nanotubes and miscible polymer blends based on poly[ethylene-co-(acrylic acid)]

Four binary polymer blends containing poly [ethylene-co-(acrylic acid)] (PEAA) as one component, and poly(4-vinyl phenol-co-2-hydroxy ethyl methacrylate) (P4VPh-co-2HEMA) or poly(2-ethyl-2-oxazoline) (PEPx) or poly(vinyl acetate-co-vinyl alcohol) (PVAc-co-VA) or poly (vinylpyrrolidone-co-vinyl acetate) (PVP-co-VAc) as the other component were prepared and used as a matrix of a series of composite materials. These binary mixtures were either partially or completely miscible within the composition range studied and were characterized by differential scanning calorimetry (DSC) and Fourier transformed infrared spectroscopy (FTIR). Carbon nanotubes (CNTs) were prepared by a thermal treatment of polyester synthesized through the chemical reaction between ethylene glycol and citric acid over an alumina boat. High resolution transmission electron microscopy (HRTEM) was used to characterize the synthesized CNTs. Films of composite materials containing CNTs were obtained after evaporation of the solvent used to prepare solutions of the four types of binary polymer blends. Young's moduli of the composites were obtained by thermomechanical analysis at room temperature. Only one glass transition temperature was detected for several compositions on both binary blends and the composite material matrices. Evidence of hydrogen bond formation was recorded for both miscible blends and composite materials. The degree of crystallinity and Young's moduli of the CNT-polymer composites increased compared to the single polymer blends. © 2008 Wiley Periodicals, Inc

Comparative study of the thermal and mechanical properties of nanocomposites prepared by in situ polymerization of ?-caprolactone and functionalized carbon nanotubes

As an effort to compare the influence of several types of functionalized carbon nanotubes (CNTs) upon the mechanical and thermal properties of nanocomposites prepared with a poly(?-caprolactone) (PCL) as matrix and functionalized CNTs as fillers; nanocomposites of PCL-CNTs were studied in this study. CNTs were synthesized by chemical vapor deposition using dry ethanol as the carbon source. High resolution scanning electron microscopy, high resolution transmission electron microscopy, and Raman and infrared spectroscopies were used to characterize the CNTs obtained. Four chemical synthesis routes were exploited to add different types of chemical groups onto the surface of purified CNTs. Specifically, the authors inserted: (i) N-methylpyrrolidine, (ii) carboxyl and hydroxyl, (iii) urethane, and (iv) phenylmethanol groups onto CNTs surface. Nanocomposites were synthesized by in situ polymerization of ?-caprolactone (?-CL) in presence of 1 wt% of each type of functionalized CNTs. Young's moduli of the nanocomposites prepared with N-methylpyrrolidine or carboxyl and hydroxyl functionalized CNTs are higher than the one of pure PCL, whereas all the mechanical properties of the nanocomposites containing urethane or phenylmethanol groups evaluated at the break point were higher than those of pure PCL. Thermal stability of all the nanocomposites studied improved with respect to pure PCL. � 2012 Society of Plastics Engineers

Poly[ethylene-co-(acrylic acid)]-based nanocomposites: Thermal and mechanical properties and their structural characteristics studied by Raman spectroscopy

Nanocomposites containing carbon nanotubes (CNTs) as nanofillers and poly[ethylene-co-(acrylic acid)] (PEAA) or a polymer miscible mixture of PEAA and poly(2-ethyl-2-oxazoline) (PEOx) as a matrix were prepared by the solution-evaporation method with minimal damage to nanotubes. CNTs were prepared by chemical vapor deposition (CVD) with ethanol as the source of carbon. Raman spectroscopy confirmed the presence of single walled carbon nanotubes (SWNTs). High resolution transmission electron microscopy (HRTEM) showed the formation of multi walled carbon nanotubes (MWNTs). Thermal and mechanical properties of the nanocomposites were studied by analyzing samples containing different amounts of CNTs. The degree of crystallinity (Xc) of the PEAA-based nanocomposite containing a smaller amount of CNTs was larger (Xc = 17.0%) than both the one of pure PEAA (Xc = 14.6 %) and PEAA-based nanocomposite containing higher amounts of CNTs (Xc = 15.0%). The Young's modulus, ultimate stress, deformation at break, and toughness obtained from unidirectional tensile tests of the CNTs (1 wt%)-PEAA nanocomposite were higher than both the one of pure PEAA and CNTs (5 wt%)-PEAA nanocomposite. When a polymer mixture of PEAA/PEOx (containing 80 wt% of PEAA) was used as a matrix, a better mechanical response was also detected for nanocomposite containing 1 wt% CNTs. The nanocomposites containing small amounts of CNTs prepared here have potential to be used as coatings of metal or glass surfaces expecting a better mechanical performance than the one of pure matrix. � 2011 Society of Plastics Engineers