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A Simple Access to the (Log/Normal) Molecular Weight Distribution Parameters of Polymers Using PGSTE NMR
Author(s) -
Gong Xiaoliang,
Hansen Eddy W.,
Chen Qun
Publication year - 2011
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201000706
Subject(s) - exponential function , robustness (evolution) , scaling , polymer , thermal diffusivity , molar mass distribution , materials science , mathematics , thermodynamics , chemistry , mathematical analysis , physics , organic chemistry , biochemistry , geometry , gene
A log/normal MWD is characterized by two parameters, its mean molecular weight M 0 and width σ . It is demonstrated how these parameters can be obtained by model fitting a stretched exponential function (SEF), as characterized by two parameters β and D S , to the PGSTE response curve. Based on simulations, two general empirical equations relating β and D S to M 0 and σ are found. The model enables the MWD characteristics to be determined if the scaling law between diffusivity and molecular weight is known. The sensitivity and relative error of σ and M 0 are discussed and the applicability of the model is illustrated by analyzing experimental NMR response curve of some PEO samples. The key advantages of this technique are its simplicity, numerical robustness, and reliability.