Search results for "component"
showing 10 items of 1682 documents
Multicomponent solid dispersion a new generation of solid dispersion produced by spray-drying
2020
Abstract The term “multicomponent solid dispersion” is widely used in recent literature to describe solid formulations consisting of a special excipient's mixture and active molecules finely dispersed. However, this term has not yet been defined. In this review, we aimed to improve the definition of multicomponent solid dispersions as a new generation of solid dispersions capable to improve both formulation issues and the therapeutic effect of the final dosage form. As it is well-known the use of solid dispersions to improve drug dissolution rate and solubility, this review describes the field of solid dispersions as well as the formulation strategies available for their production. In part…
Processing and properties of blends with liquid crystal polymers
1990
Experimental data on the processing behavior and on the rheological and mechanical properties of blends with a liquid crystal polymer as one component are presented. The blends with low amounts of LCP show easier processability and lower viscosity than the thermoplastic matrix. The elastic modulus is also improved. The reduction of viscosity has been attributed to the lower pressure entry, due to the formation of fibrils and to the immiscibility of the two phases.
QENS from polymer aggregates in supercritical CO2
2000
Abstract We report QENS measurements from PS-b-PFOA aggregates in supercritical CO2. Line shapes are dominated by localized diffusive modes and segmental dynamics of the anchored, finite-length PFOA chains. For Q⩽0.6 A−1, we obtain effective diffusion coefficients of ≅0.8 10−6 cm2/s. At higher Q, a single component is not sufficient as shown by excess intensity on the flanks. For Q⩾1.5 A−1, the wings reflect contributions due to a distribution of faster, more localized chain modes.
Cellulose/Water: Liquid/Gas and Liquid/Liquid Phase Equilibria and Their Consistent Modeling
2007
Liquid/liquid and liquid/gas equilibria were measured for the water/cellulose system at 80 °C using three different polymer samples. For these experiments we prepared cellulose films of approximately 20−25 μm in thickness and determined their equilibrium swelling in water. Thereafter the polymer concentration in the mixed phase was increased by means of a stepwise removal of the volatile component, and the equilibrium vapor pressures were measured using an automated combination of head space sampling and gas chromatography. Contrary to the usual behavior of polymers, the swelling of cellulose increases as its molar mass becomes larger. The Flory−Huggins interaction parameters calculated fro…
A new strategy for the synthesis of fluorinated 3,4-dihydropyrimidinones
2009
A new family of 3,4-dihydropyrimidinones (DHPMs) bearing fluorinated substituents at C6 have been prepared from gem-difluorinated nitriles, alkyl 3-butenoates and iso(thio)cyanates. This novel Biginelli-type process relies on the gamma-addition of the ester-derived enolate to fluorinated nitriles. A tandem nucleophilic addition aza-Michael reaction sequence completes the synthetic process. (C) 2009 Elsevier B.V. All rights reserved.
Static Digestion Models: General Introduction
2015
Several in vitro methods have been developed to simulate the physiological conditions of the human gastrointestinal digestion, the simplest being the static methods. The following chapter clarifies the concepts of bioaccessibility and dialyzability, and describes the conditions (pH, enzymes, agitation, etc.) to be applied in oral, gastric and intestinal phases when assessing a food component (nutrient, bioactive or toxin) or a food product, in a single or multi-phase model. The advantages and disadvantages of the static models vs. dynamic and in vivo models are discussed, and a review of specific conditions applied on nutrients (minerals, vitamins, proteins, fatty acids, etc.) and bioactive…
New Viscoelastic Materials Obtained by Insertion of anα-Olefin in atrans-Polyisoprene Chain with a Single-Component Organolanthanide Catalyst
2001
Copolymerisation of isoprene with C 6 -C 18 a-olefins by a single component organolanthanide catalyst affords poly(trans-1,4-isoprene) containing 6-10% of inserted olefin. The mechanical properties of highly crystalline transpolyisoprene are dratically modified after insertion of the alkyl chains, leading to quasi-amorphous viscoelastic materials.
Investigation of the glass transition and melting of polymers by nuclear magnetic resonance
2007
Investigations of the glass transition and melting of partially crystalline polymers by nuclear magnetic resonance provide valuable information on the nature of noncrystalline regions. The broad line NMR signal was separated into a narrow component and a broad component by using a new method which does not imply the ambiguity usually present. From the intensity of the narrow component the mobile fraction was determined. This fraction was extrapolated to “infinite” temperature. By subtracting the mobile fraction from the noncrystalline fraction, the noncrystalline rigid fraction was obtained. Comparison of the measured second moments of the two components of the NMR line with calculated seco…
One-Pot Three-Component Solvent-Free Syntheses of n-Alkyl-Bridged N,N,N,N-tetra(2-hydroxybenzyl)diamines and N,N-bis(2-hydroxybenzyl) amines
2010
A simple solvent-free method to prepare four N,N,N’,N’-tetra(2-hydroxy-3,5dimethylbenzyl)diaminoalkanes and four N,N,N’,N’-tetra(2-hydroxy-5-t-butyl-3-methylbenzyl)-diaminoalkanes containing a long n-alkyl-bridge (58 CH2 groups between N-atoms) is described. In addition, preparations of four dihydrochlorides of prepared n-alkyl-bridged N,N,N’,N’-tetra(2-hydroxybenzyl)diamines are described. This method was also tested in the preparation of eight previously reported N,N-bis(2-hydroxybenzyl)amine derivatives.
Theory and Simulation of Multiphase Polymer Systems
2010
The theory of multiphase polymer systems has a venerable tradition. The 'classical' theory of polymer demixing, the Flory-Huggins theory, was developed already in the forties of the last century. It is still the starting point for most current approaches -- be they improved theories for polymer (im)miscibility that take into account the microscopic structure of blends more accurately, or sophisticated field theories that allow to study inhomogeneous multicomponent systems of polymers with arbitrary architectures in arbitrary geometries. In contrast, simulations of multiphase polymer systems are relatively young. They are still limited by the fact that one must simulate a large number of lar…