Crystallinity solubility

Parallel studies on PAMAM dendrimers, the Frechet type polyether den-drons, and other dendrimer families have generated an extensive list of unique properties driven by the dendritic state/ Figure 1.18 compares several significant physical property differences between the linear and dendritic topologies related to conformations, crystallinity, solubilities, intrinsic viscosities, entanglement, diffusion/mobility and electronic conductivity. 

DL-Polylactic acid, for the most part, was found to erode in about 12 months. Slow degradation of DL-polylactic acid often becomes a limitation on its use. This rate can be accelerated appreciably by copolymerizing with up to 50 mol% glycolide to yield complete erosion in as fast as 2 to 3 weeks. Incorporation of glycolide into the polylactide chain alters crystallinity, solubility, biodegradation rate, and water uptake of the polymer. 

Amides of Sulphur Acids. — Similarly, amido-derivatives can be obtained from sulphur trioxide. The action of ammonia on that compound yields ammonium sulphamate, H4N—O—(S02)—NH or, if less ammonia be used, sulphamie acid, HO—(S02)—NH2 they are both crystalline, soluble compounds. 

Molecular weight information is especially useful since variances in molecular weight are shown to impact adhesion and brittleness properties (Kroschwitz, 1990), solubility (Flory, 1970), and sorption and mass transfer characteristics of organic solutes (Kilduff and Weber, 1992). The impacts of varying molecular weight on polymer crystallinity, solubility, and, to a lesser extent, the glass transition temperature are discussed in the following sections. 

The salts are crystalline, soluble compounds. Hydroxyl amine is of especial importance in connection with the study of aldehydes, and will be mentioned again al that time. 

Powdery or crystalline, soluble in water and sweet in taste. 

Several strategies were appUed to produce samples for TEM and kinetic studies [8, 21], but only one route is presented here (Fig. 15.3). Noble metal nanoparticles were grown via metal evaporation on a crystalline soluble substrate (e.g., NaCl(OOl)), leading to an epitaxial growth of particles with regular shape and well-developed low-Miller index facets (Fig. 15.3). Thereafter, the metal particles were embedded in a thin (25 nm) amorphous oxide fdm, before the metal-oxide system was lifted off the substrate via flotation in water [8, 18, 20, 31]. 

In order to prepare oxide model systems well-suited for characterization by high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), AFM or X-ray photoemission spectroscopy (XPS), as well as for kinetic studies by gas chromatography (GC), oxide films and oxide nanoparticles were vacuum-grown on a crystalline soluble substrate (e.g., NaCl(OOl)) via oxide (or metal) evaporation in a low background pressure ( 10" Pa) of oxygen. 

This survey of the pharmaceutical aspects of polymers and macromolecules emphasises their use in formulation. It stresses the key features of polymers - their molecular weight distribution and their versatility in terms of their morphology, crystallinity, solubility and performance. 

Properties Bright lemon-yellow, dull or earthy luster (pearly or silky when coarsely crystalline). Soluble in acids. Radioactive. Usually occurs as a powder or in fine-grained aggregates. 

Drug name Crystalline solubility (pM) Amorphous solubility (pM) Solubility ratio (amorphous/ crystalline)... 

Figure 2.11 Crystalline solubility match pairs showing effects of the ortho-methyl substituent.

High-molecular-weight poly (thiol esters) show fiber-forming properties. This section covers the available data concerning melting points, crystallinity, solubility, and stability of this class of esters, and compares them with polyesters and polyamides. Information about spectra is also reviewed. 

Crystallinity Solubility product of salt forms Gut metabolism... 

Adumlnates are for the most part crystalline, soluble compounda obtained by the action of metallic oxides or hydrates upon alumina. Pofoa-... 

In the present study, synthetic analcites having fixed Al/Si ratios of 2/3, 1/2, and 1/3 were subjected to ion exchange with a series of cations of various size, charge, and polarizability to fix limits of crystalline solubility and to determine the effects of compositional change on structure. Structure data as a function of temperature and pH2o (to be presented in a future publication) are available in a doctoral thesis by Balgord (2). 

Ion exchange runs were carried out under various conditions using salts of several monovalent and divalent cations with the dual objectives of preparing materials for dehydration and stability studies (to be described in a subsequent paper) and defining the limits of true crystalline solubility in the analcite structure. 

Aluminates are for the most part crystalline, soluble compounds, obtained by the action of metallic oxids or hydroxids upon alumina. Potassium aluminate, KaAlaOa-fSAq, is formed by dissolving recently precipitated aluminium hydroxid in potash solution. It forms white crystals very soluble in HaO, insoluble in alcohol caustic and alkaline. By a large quantity of HaO it is decomposed into aluminium hydroxid, and a more alkaline salt, KgAltOa. 

Methods for determining the presence, kind, and amount of configurational base units can be classified as relative or absolute. Absolute methods do not require calibration with polymers of known tacticity. Relative methods, on the other hand, require comparison with standard substances. X-ray crystallography, nuclear magnetic resonance, infrared spectroscopy, and optical activity measurements are all absolute methods. Relative methods include crystallinity, solubility, glass transition temperature, and melting temperature measurements as well as chemical reactions (Table 3-2). 

Crystalline soluble proteins which account for almost 90% of the total vertebrate lens protein. Lens cells are not replaced, so they must survive the lifespan of the animal. Moreover, C. cannot be replaced, because lens cells lose their nuclei and other organelles if these were present they would presumably cause discontinuities in refractive index. C. must therefore be exceptionally stable, withstanding all abuses which could lead to denaturation or aggregation. They must also have short range order in solution to insure a smoothly changing refractive index. 

The crystalline melting point is decreased by the presence of a comonomer and non-crystalline, soluble copolymers can be prepared. 

Drug (Crystalline) Solubility Within a Polymer Matrix... 

The residue films are then analyzed for crystallinity, solubility, dissolution, supersaturation behavior, and solid-state stability. Two recent publications on solvent casting-based screening approaches are described in more detail in the following subsections. 

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