Preparation of organoclays in sc CO2 and implication of onium stability on the properties of PA6 nanocomposites

Poster (2009, May 14)

Preparation of poly(D,L)lactide microspheres and their clinical applications as a convenient embolic material

in Journal de Pharmacie de Belgique (1990), 6

Owing to their shape, accurately calibrated microspheres appear to be very suitable material for distal embolization. Moreover, the biocompatible (D,L) polylactide (PLA) microspheres possess two other ... [more ▼]

Owing to their shape, accurately calibrated microspheres appear to be very suitable material for distal embolization. Moreover, the biocompatible (D,L) polylactide (PLA) microspheres possess two other valuable advantages: easy adjustment of their biodegradation rate, and incorporation of chemotherapeutic agents during their production. The authors describe the preparation of these (D,L) PLA microspheres and their clinical applications as a preliminary step to arterial chemoembolization. [less ▲]

Preparation of poly(D,L-lactide) nanoparticles assisted by amphiphilic poly(methyl methacrylate-co-methacrylic acid) copolymers

in Journal of Biomaterials Science. Polymer Edition (2001), 12(4), 429-450

When co-precipitated with amphiphilic copolymers from DMSO, poly(D,L-lactide) (PLA) can be readily converted into stable sub-200 nm nanoparticles by addition of an aqueous phase, free of any polymeric ... [more ▼]

When co-precipitated with amphiphilic copolymers from DMSO, poly(D,L-lactide) (PLA) can be readily converted into stable sub-200 nm nanoparticles by addition of an aqueous phase, free of any polymeric stabilizers such as poly(vinyl alcohol) or Poloxamer. In this work, the ability of random poly(methyl methacrylate-co-methacrylic acid) copolymers (PMMA-co-MA) to stabilize PLA nanoparticles was demonstrated, and the properties of PLA/PMMA-co-MA nanoparticles were investigated. When co-precipitated with PMMA-co-MA, PLA was totally converted into nanoparticles using a polymer concentration in DMSO (Cp) below 17.6 mg ml(-1), and a PMMA-co-MA proportion above a critical value depending on the content of MA repeating units (X). For instance, the lowest PMMA-co-MA proportion required was 0.9 mg mg(-1) PLA for X = 12%, and 0.5 mg mg(-1) PLA for X = 25% (for C(PLA) = 16 mg ml(-1) DMSO). The nanoparticle diameter was essentially independent of X, the proportion of PMMA-co-MA, and the PLA molecular weight, except for oligomers for which the nanoparticle diameter was smaller. It decreased when the organic phase was diluted (126 +/- 13 nm for Cp = 17.6 mg ml(-1), and 81 +/- 5 nm for C(P) = 5.6 mg ml(-1)). The time-dependence of the stability and the degradation of PLA/PMMA-co-MA nanoparticles was discussed. One of the main advantages of this technique is the ability to control surface properties and to bring functional groups to otherwise non-functionalized PLA nanoparticles. To illustrate this, a conjugate of PMMA-co-MA25 and biotin was synthesized, and used to prepare biotinylated nanoparticles that could be detected by fluorescence and transmission electron microscopy after infiltration into ligatured rat small intestine. [less ▲]

Preparation of preexfoliated poly(ε-caprolactone)/clay masterbatches in supercritical carbon dioxide

Poster (2005, May 11)

Preparation of reactive surfaces by electrografting: a route to biosensors

Poster (2003, May 16)

Preparation of reproducible alkaline phosphatase-antibody conjugates for enzyme immunoassay using a heterobifunctional linking agent

in Analytical Biochemistry (1988), 172(2), 392-396

Conjugates of alkaline phosphatase (AP) and mouse monoclonal immunoglobulins G (IgG) were prepared by means of the heterobifunctional linker, N-succinimidyl 3-(2-pyridyldithio)-propionate. The efficiency ... [more ▼]

Conjugates of alkaline phosphatase (AP) and mouse monoclonal immunoglobulins G (IgG) were prepared by means of the heterobifunctional linker, N-succinimidyl 3-(2-pyridyldithio)-propionate. The efficiency of such conjugates can be improved by optimizing the degree of substitution of IgG and AP. We have determined conditions yielding better performing conjugates than those synthesized by methods described previously. Moreover, the results obtained with the technique presented here are quite reproducible with all four monoclonal antibodies tested. [less ▲]

Preparation of Spherical Submicronic Barium Zirconate particles in Highly Basic Solution below 100°C

in IOP Conference Series: Materials Science and Engineering (2011)

In this study, a new method has been developed to produce pure crystalline BaZrO3 powders from Ba+Zr solution or weakly soluble reactants by using precipitation route in highly basic aqueous solution. The ... [more ▼]

In this study, a new method has been developed to produce pure crystalline BaZrO3 powders from Ba+Zr solution or weakly soluble reactants by using precipitation route in highly basic aqueous solution. The influence of several synthesis parameters is studied. At high OH- concentration ([NaOH] = 20 mol/l), it is possible to obtain the well-crystallized stoichiometric perovskite phase at relatively low temperature (~80°C), after a short reaction time (15 minutes) and without requiring any precaution to avoid the presence of CO2. This synthesis method yields spherical particles, whose size can be controlled by changing the concentration of the Ba+Zr solution. No calcination treatment is necessary since the precipitate is crystalline. Suitable choice of the synthesis parameters ([NaOH] = 20 mol/l, [Ba+Zr] = 1 mol/l, reaction time = 15 minutes) yields a sub-micron precipitate. [less ▲]

Preparation of supported yttrium alkoxides as catalysts for the polymerization of lactones and oxirane

in Journal of Polymer Science. Part A, Polymer Chemistry (2003), 41(4), 569-578

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring-opening polymerization of oxirane and e ... [more ▼]

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring-opening polymerization of oxirane and e-caprolactone. In the two methods, [tris(hexamethyldisilyl)-amide]yttrium [Y[N(SiMe3)(2)](3)} is the metal alkoxide precursor. It is directly reacted with the silanol groups of the support, in the first method, and this is followed by alcoholysis of the unreacted amide groups. The flexibility of this method seems to be limited because the grafting density and the structure of the grafted Y alkoxide (less than one alkoxide by metal) are independent of the experimental conditions. In the second method, Y[N(SiMe3)(2)](3) is first reacted with 1 or 2 equiv of alcohol with the formation of the mixed Y alkoxide/amide. The amide functions are used to attach Y to the support. This method is free from side reactions, quite reproducible, and well suited to support one type of active species (monoalkoxide or dialkoxide). Preliminary experiments with e-caprolactone polymerization have confirmed the activity of the supported Y alkoxide, whatever preparation method is used. (C) 2003 Wiley Periodicals, Inc. [less ▲]

Preparation of YBa2Cu3O7-x superconducting thick films by the electrophoretic deposition method

in Journal of Materials Science (2006), 41(24), 8109-8114

YBa2Cu3O7-x thick films have been realised by the Electrophoretic Deposition method (EPD). The influence of several parameters (powder and iodine concentrations in the suspension, applied voltage and ... [more ▼]

YBa2Cu3O7-x thick films have been realised by the Electrophoretic Deposition method (EPD). The influence of several parameters (powder and iodine concentrations in the suspension, applied voltage and deposition time) on the EPD process has been studied by measuring the conductivity of the suspension and the amount of YBa2Cu3O7-x particles deposited on the electrode. Superconducting coatings onto silver substrates have been produced by a multilayer process during different deposition times. The highest critical current density value of these coatings measured by the four-point probe method is about 10^3 A/cm^2 (77 K), in a suitable range for magnetic shielding applications. [less ▲]

Préparation, caractérisation et réactivité de l'acide 1-vanado-11-molybdo-phosphorique supporté sur des matériaux silicatés mésoporeux dans l'oxydation du propène

in Comptes Rendus Chimie (2012), 15(8), 658-668

The H 4PMo 11VO 40 heteropolyacid (HPA) was supported at 30 wt.% by the dry impregnation method on HMS, CMI-1 and SBA-15 mesoporous materials. The state of the HPA and those of the supports were examined ... [more ▼]

The H 4PMo 11VO 40 heteropolyacid (HPA) was supported at 30 wt.% by the dry impregnation method on HMS, CMI-1 and SBA-15 mesoporous materials. The state of the HPA and those of the supports were examined by nitrogen physisorption, X-ray diffraction, (DR) FT-IR and X-ray photoelectron spectroscopies, thermal analysis (TG-ATD) and scanning electron microscopy (SEM). The effect of support on the catalytic behavior of H 4PMo 11VO 40 was studied in the propene oxidation at 350 °C. It was shown that the presence of H 4PMo 11VO 40, modifies the textural properties of mesoporous materials (decrease of surface area) without destroying their structure. The interaction support-heteropolyacid leads to the formation of (SiOH 2+)(H 3PMo 11VO 40 -) surface species more stable than H 4PMo 11VO 40 species and that appear to be the active sites in the propene oxidation. © 2012 Published by Elsevier Masson SAS on behalf of Academie des sciences. [less ▲]