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polydisperse, a.|pɒlɪdɪˈspɜːs|
[ad. G. polydispers (W. O. Ostwald Grundriss d. Kolloidchem. (ed. 2, 1911) i. 39), f. poly- poly- + dispers disperse (cf. disperse v. 9).]
Existing in the form of or containing colloidal particles (which may be macromolecules) having a range of sizes; applied esp. to macromolecular substances in which there is a simple distribution of particle size (or occas. some other specified physical property) with one peak; also applied to such a property or its distribution. Also polydiˈspersed a. Cf. polymolecular a. d.
1915M. H. Fischer tr. Ostwald's Handbk. Colloid-Chem. i. 35 These systems in which the disperse phase is composed of particles having different degrees of dispersion may be called polydisperse systems. 1938Nature 4 June 1001/2 The specific polysaccharide of type I pneumococcus is polydisperse with an average weight of approximately 225,000. 1941Jrnl. Franklin Inst. CCXXXI. 1 Fine powders and colloidally dispersed material are also typically polydispersed. 1948Chem. Abstr. XLII. 1787 (heading) Birefringence of flow in polydispersed mixtures. 1962H. Bloemendal et al. in A. Pirie Lens Metabolism Rel. Cataract 303 Prolonged dialysis of 7 M urea-treated α-crystallin against 1·25 M urea results in the appearance of a polydisperse peak with sedimentation coefficient of 10 S. 1963Nature 16 Nov. 665/2 A preparation may be monodisperse with respect to one parameter, polydisperse with respect to a second and heterogenous with respect to a third; the foregoing terms are only meaningful if the parameter measured is..specified. 1968H. Harris Nucleus & Cytoplasm iii. 56 Preparations of the total RNA in the cell cytoplasm..did not show any fraction which had either the kinetic characteristics or the polydisperse sedimentation of the rapidly labelled nuclear RNA. 1973Sci. Amer. June 112/1 With a calibrated grid in the viewing field of the microscope one can measure the relative sizes of the particles in a polydisperse suspension (a suspension containing particles of widely varying size).
Hence polydiˈspersity, the condition or property of being polydisperse.
1927H. S. van Klooster tr. Kruyt's Colloids x. 154 Viewed in the ultramicroscope, this sol presents a very colorful picture which reveals the poly-dispersity very plainly. 1936Trans. Faraday Soc. XXXII. 49 It appears that determinations of polydispersity by measurement of sedimentation velocity can only be effected in extremely dilute solutions. 1963Nature 16 Nov. 665/2 Some degree of random variability in secondary or tertiary structure may confer polydispersity with respect to frictional coefficient on some proteins. 1967Margerison & East Introd. Polymer Chem. ii. 47 The value of the parameter Mw/Mn in a practical case thus gives a measure of the range of molecular weights in the sample;..a value of two or greater indicates considerable polydispersity. 1976[see polymolecularity]. |
