Chemical stability of poly

In spite of the documented, relatively high chemical stability of poly(PFSA) membranes in the fuel-cell environment, recent extensive work looking into the origins of performance loss observed in PEFCs has revealed important mechanisms of degradation that apply to perfluorinated membranes (while being further amplified in nonperfluorinated membranes). An important mechanism of membrane... 

M. D. Coffin, and J.W. McGinity, Biodegradable pseudolatexes The chemical stability of poly (D,L-lactide) and poly (s-caprolactone) nanoparticles in aqueous media. Pharmaceutical Research, 9 (2), 200-205,1992. 

The high thermal and chemical stability of fluorocarbons, combined with their very weak intermolecular interactions, makes them ideal stationary phases for the separation of a wide variety of organic compounds, including both hydrocarbons and fluorine-containing molecules Fluonnated stationary phases include per-fluoroalkanes, fluorocarbon surfactants, poly(chlorotrifluoroethylene), polyfper-fluoroalkyl) ethers, and other functionalized perfluoro compounds The applications of fluonnated compounds as stationary phases in gas-liquid chroma... 

Lai, M.C., Hageman, M.J., Schowen, R.L., Borchardt, R.T., and Topp, E.M. 1999a. Chemical stability of peptides in polymers. 1. Effect of water on peptide deamidation in poly(vinyl alcohol) and poly(vinyl pyrrolidone) matrixes. J. Pharm. Sci. 88, 1073-1080. 

Peracchia MT, Vauthier C, Puisieux F, Couvreur P (1997) Development of sterically stabilized poly(isobutyl 2-cyanoacrylate) nanoparticles by chemical coupling of poly(ethylene glycol). J Biomed Mater Res 34 317-326. 

Stationary phase materials are synthesized from different raw materials. Those stationary phase materials synthesized from inorganic materials, such as silica and alumina, are physically strong but chemically unstable. Conversely, stationary phase materials synthesized from organic materials, such as polystyrene or poly(vinyl alcohol), are chemically stable but physically weaker. Improvements in the chemical stability of inorganic stationary phase materials and in the physical strength of organic stationary phase materials are required the marketed products do not have both and have to be used under restricted conditions in liquid chromatography. 

Reactions with monofunctional reagents are for example carried out in order to increase the thermal and/or chemical stability of the end groups (Poly-oxymethylenes, Example 5-7). Reactions with bifunctional reagents can be used to enlarge the degree of polymerization or to synthesize block copolymers (see Sect. 4.2.1). 

Poly(vinylidene fluoride) (PVDF) is the second most important thermoplastic within the fluoropolymer family after PTFE. Although, both the thermal and chemical stability of PVDF are somewhat lower compared to PTFE, the hydrogenated polymer can be more easily processed with conventional equipment, and it offers an advantageous compromise between quality and price. When the... 

It should be noted that PCMU based on cross-linked macroligands possess a relatively high chemical and thermal stability. The stability of poly(enol-ketonate) chelates obtained by oxidation of thin polyvinylacetate films increases in the series of mono-, di- and trivalent ions [122], the oxidation promoting the penetration of the metal ions into the deep film layers. The weight loss of Co and Mn polychelates based on the condensation products of stoichiometric amounts of 5,5 -methylene-bis-salicylaldehyde and 4,4 -diaminophenyl ether at 300, 500, and 600 °C is 2.1, and 0.5 8.0 and 9.8 25.0 and 27.5%, respectively [14b]. The stability, in the range between 275 and 640 °C, of chelates formed by the transition metals and condensation products of p-hydroxybenzoic acid, urea and formaldehyde follow the series [123] Fe(III)>Co(II)>Cu(II)>Ni(II)>V02(II)> Zn(II) Mn(II) > CML. 

The chemical stability of the polymers of both nitrocthyleno and 2-nitro l-propene is low. Tliis is partly due. to the traces of catalysis present in the polymers which can act as decomposition catalysis. Poly(nitrocthylcnc) turns... 

Around 1960 Carl Marvel at Illinois discovered that the reaction between 3,3, 4,4 -tetraaminobiphenyl (diaminobenzidine) (186) and diphenyl isophthalate yielded the strong, stable poly benzimidazoles. The thermal and chemical stability of their fibers make them suitable for parachutes, space suits and firefighting clothing. Several novel polymerizations were reported, including with 1,2,5,6-tetraaminoanthraquinones. 

Lai MC, Hageman MJ, Schowen RL, Borchardt RT, and Topp EM. Chemical Stability of Peptides in Polymers. 1. Effect of water on Peptide Deamidation in Poly(vinyl alcohol) and Poly(vinyl pyrrolidone) Matrixes. J Pharm Sci 1999a 88 1073-1080. 

Similar behavior has been observed for noncrystallizing polymers. For example, the diffusivity of water in poly(vinylpyrrolidone) (PVP) (Oksanen and Zografi, 1993) has been shown to increase at water contents beyond the hydration limit. Additional reports have shovm that the hydration limit has physical significance for other polymer excipients. Microcrystalline cellulose and lactose for compression, for example, lose their direct compaction properties at water contents just below (Huettenrauch and Jacob, 1977), and gelatin capsules become brittle as the water content is reduced below Wm (Kontny and Mulski, 1989). Recently, the chemical stability of a model peptide in PVP matrices was shown to improve when the amorphous dispersion was stored below the polymer s hydration limit (Lai et al., 1999a Lai et al., 1999b Lechuga-Ballesteros et al., 2002). 

Y. Aso, S. Yoshioka, and T. Terao, Release characteristics stability of poly(l-lactide) microspheres and chemical stability of drugs in the microspheres, Proc. Int. Symp. Control. Release Bioact. Mater. 19, 310 (1992). 

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