Fibrous polymers

Water-Holding Capacity (WHC). AU polysaccharides are hydrophilic and hydrogen bond to variable amounts of water. HydratabUity is a function of the three-dimensional stmcture of the polymer (11) and is kifluenced by other components ki the solvent. Fibrous polymers and porous fiber preparations also absorb water by entrapment. The more highly crystalline fiber components are more difficult to hydrate and have less tendency to sweU. Stmctural features and other factors, including grinding, that decrease crystallinity or alter stmcture, may iacrease hydratioa capacity and solubUity. 

The concept of fibrous polymer formulations was extended to the delivery of aquatic herbicides (56). Several herbicides including Diquat, Fluridone, and Endothal were spun into biodegradable poly-caprolactone. Monolithic fibers and a modified monolithic system were produced with levels of herbicide from 5 to 60% by weight. Laboratory and field trials showed efficacious delivery of the active agent. Fibers provided both targeted localized delivery and controlled release of the herbicide to the aquatic weed. 

A. G., and Perkins, B. H., Biodegradable fibers for the controlled release of tetracycline in treatment of peridontal disease, Proc. Int. Symp. Control. Rel. Bioact. Mater., 14, 289, 1987. Dunn, R. L., Lewis, D. H., and Beck, L. R., Fibrous polymer for the delivery of contraceptive steroids to the female reproductive tract, in Controlled Release of Pesticides and Pharmaceuticals (D. H. Lewis, ed.). Plenum Press, New York, 1981, pp. 125-146. 

Radiation induced graft polymerization of vinyl monomers and fibrous polymers, Industrial uses of large radiation sources. Vol. I. p. 257.1.A.E.A. Vienna 1963. 

NC is a water-insoluble fibrous polymer. Consequently it is not absorbed thru the intestinal wall or cell membranes. This accounts for its total lack of oral toxicity to mammals. Subchronic and chronic feeding to rats and dogs at contents as high as 10% and to mice at 3% of the solid diet resulted in no effects other than those of fiber bulk, ie, as if they had been fed cotton linters. 

Problem Areas in Structure Analysis of Fibrous Polymers... 

The same data collection and reduction techniques are commonly used by the same workers for many different polymers. Therefore, data for these other polymers may contain errors on a similar scale, but that the errors have usually, but not always, gone undetected (8). If more than 500 reflections are observed, from single crystals of simple molecules, recognizable electron-density distributions have been derived from visually estimated data classified only a "weak", "medium" or "strong". The calculation of the structure becomes more sensitive to the accuracy of the intensity data as the number of data points approaches the number of variables in the structure. One problem encountered in crystal structure analyses of fibrous polymers is that of a very limited number of reflections (low data to parameter ratio). In addition, fibrous polymers usually scatter x-rays too weakly to be accurately measured by ionization or scintillation counter techniques. Therefore, the need for a critical study of the photographic techniques of obtaining accurate diffraction intensities is paramount. 

Brannon, R. C. "The Development of An Integrated Intensity Technique and Its Application In Determining the Crystal Structure of Fibrous Polymers", thesis, University Microfilms, Ann Arbor, MI, 1979. 

Fibrous polymers are, at best, paracrystalline, exhibiting lattice distortions of the second kind which destroy long range order (1, 2). 

New methods of computational analysis will be sought in order to provide simultaneous measures of crystallinity, crystallite-size and lattice distortion in fibrous polymers from X-ray diffraction patterns, but these must pass the test of application to fibres which can be partly characterized by means of electron-microscopy. 

HAGEGE, R. "Diffraction Methods for Structural Determination of Fibrous Polymers" American Chemical Society Washington, 1979, in Press. 

Although various procedures are available for the model analysis of fibrous polymers, methods based on the virtual bond representation of the asymmetric residue may be of advantage in many cases. In the following, we describe one such method that began with simple procedures applied to polysaccharides, but has now been refined into a flexible and powerful model analysis tool that is simple to use with any class of polymer. Its use in the present case, however, is illustrated with examples drawn from the structure analysis of polysaccharides. 

This collection of papers was part of a unique symposium held during the 178th Meeting of the American Chemical Society. The symposium, Diffraction Methods for Structural Determination of Fibrous Polymers, had a pronounced international character, with scientists from 12 different countries. The speakers represented both the synthetic polymer and biopolymer fields, with contributions in each of the three classes of natural polymers nucleic acids, proteins, and polysaccharides. Most important, the symposium centered on methods and techniques for studying fibrous polymers, methods that are usually taken for granted despite their inadequacies. 

Copolymerization of I with styrene. A glass ampoule was charged with 1.45g (5m mol) of 1,0.53g (5m mol) of styrene, and 33 mg of AIBN (2 mol %) dissolved in 2.0 ml of dioxane. The ampoule was sealed under vacuum after a freeze-thaw cycle and the copolymerization was carried out at 58°C for 3 hours. The jelly-like polymer mixture was dissolved in NMP and the polymer was isolated by precipitation into methanol. After drying in vacuo, 1.76g (89%) of a white fibrous polymer were collected. The polystyrene equivalent molecular weight (Mw) is 1.3 x 10 by GPC. 

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