End-group assays

This technique is of limited value and can only be used when the polymer has an end group amenable to analysis. It can be used to follow the progress of linear condensation reactions when an end group, such as a carboxyl, is present and can be titrated. It is used to detect amino end groups in nylons dissolved in wt-cresol, by titration with methanohc perchloric acid solution, and can be applied to vinyl polymers if an initiator fragment, perhaps containing halogen, is attached to the end of the chain. [Pg.230]

The sensitivity of the method decreases rapidly as the chain length increases and the number of end groups drops. A practical upper limit might reach an of about 15,000 g mol. [Pg.230]

Molecular weight by Archibald end group assay Sedimentation studies... [Pg.286]

Comparison of Chemical End-group Assay and Corresponding Molecular-Weight Determinations for Amylose... [Pg.355]

The synthesis of linear 4 —> 1-a-D-glucans from D-glucopyranosyl phosphate by the action of phosphorylases has been shown by comparison of results of methylation and end-group assay and viscosity determination,209 and by potentiometric, iodine titrations82 on the product. The chain length of the enzymic product (100 to 200 D-glucose units) is less than that of the natural component. Whether this is due to impure enzymes cannot yet... [Pg.380]

Telomerization was effective to regulate quantitative incorporation of functional groups to one end of PIPAAm chains [7,8]. Molecular weight of the semitelechilic PIPAAm determined from GPC data was in good agreement with that determined by the end-group assay. This indicates that each macromolecule carries one amino or carboxyl end group. [Pg.27]

CPAEs 1-6, as estimated by end-group assay, were 3750, 1030, 2870, 850, 830, and U80, respectively. Nylon oligomers with low molecular weight are expected to be biodegradable. [Pg.148]

Oxidation of 2-acetamido-2-deoxy-D-glucose derivatives with hypoiodite at 0° proceeds quantitatively, without side reactions, and is satisfactory as a procedure for end-group assay in oligosaccharides containing amino sugar residues.177 The possibility that (1 —> 3)-linked disaccharides may be degraded under the reaction conditions must not be overlooked. [Pg.259]

By methylation end-group assay. 1 Number-average degree of polymerization of methylated polysaccharide by id (isothermal distillation) or op (osmotic pressure) methods. c Viscosity-average degree of polymerization. [Pg.446]

The value of number-average molecular weights of methylated polysaccharides, used in conjunction with methylation end-group assays in the assessment of the degree of branching, has been stressed previously (see p. 435). Etherification is, however, normally carried out under alkaline con-... [Pg.464]

Derivative Solvent Molecular weight D. P. End-group assay on the methyl ether... [Pg.306]

Polysaccharide Derivative studied Method Solvent Molecular weight Degree of polymerization Remit from end-group assay Structure Refer- ence... [Pg.312]

The Colorimetric Determination of Methylated Sugars An Improved Micromethod of End-group Assay, J. K. Bartlett, L. Hough, and J. K. N. Jones, Chem. Ind. (London),... [Pg.15]

Methylation. Methylation methods should be applied to the purified fractions, particularly as an end-group assay, but also for whatever information may be gained relative to the degree of branching. [Pg.276]

III. Structural Analysis by Chemical Methods 1. End-group Assay... [Pg.280]

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