ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Model polycondensates of 1,10-decanediol and 1,3,5-benzenetriacetic acid stabilised by means of diazodiphenylmethane and ketene are utilised to extend further our understanding of the critically branched state and to investigate possible contributions of the ultracentrifuge to the study of highly polydisperse macromolecules in non-ideal, dilute solutions. By way of computerised curve fitting, the concentration gradient curve is obtained from its concentration profile in the ultracentrifuge cell. From this the weight average molecular weight M̄1 is calculated by the hinge point method. It is also confirmed that values of the two next higher moments of the molecular weight distribution, viz. M̄2/1 and M̄3/2 (i.e. Mz and Mz+1) can hardly be distinguished from infinity for these samples. Application of the hinge point method to systems of high polydispersity is found both theoretically and experimentally to furnish M̄1 after a dual extrapolation of the measured M̄1app against the generalised speed parameter λ and the initial concentration c0. It is found theoretically that for estimation of the higher molecular weight moments, plots of M̄1app M̄2/1app and M̄1app M̄2/1app M̄3/2app (not merely M̄2/1app and M̄3/2app) must be extrapolated against the same variables, i.e. λ and c0. The quantitative results thus obtained are discussed in the context of previous results on these materials. They are compared with the classical theory for random f-functional polycondensates and statistical cut-off effects on the high molecular weight tail of distribution are assessed.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1977.021781010
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