CPL - Chalmers Publication Library

The gamma distribution model for pulsed-field gradient NMR studies of molecular-weight distributions of polymers

Författare och institution:
Magnus Röding (Institutionen för matematiska vetenskaper, matematisk statistik, Chalmers/GU); Diana Bernin (Institutionen för kemi- och bioteknik, Teknisk ytkemi); Jenny Jonasson (Institutionen för matematiska vetenskaper, Chalmers/GU); Aila Särkkä (Institutionen för matematiska vetenskaper, Chalmers/GU); D. Topgaard (-); Mats Rudemo (Institutionen för matematiska vetenskaper, matematisk statistik, Chalmers/GU); Magnus Nydén (Institutionen för kemi- och bioteknik, Teknisk ytkemi)
Publicerad i:
Journal of Magnetic Resonance, 222 s. 105-111
ISSN:
1090-7807
Publikationstyp:
Artikel, refereegranskad vetenskaplig
Publiceringsår:
2012
Språk:
engelska
Fulltextlänk:
Fulltextlänk (lokalt arkiv):
Sammanfattning (abstract):
Self-diffusion in polymer solutions studied with pulsed-field gradient nuclear magnetic resonance (PFG NMR) is typically based either on a single self-diffusion coefficient, or a log-normal distribution of self-diffusion coefficients, or in some cases mixtures of these. Experimental data on polyethylene glycol (PEG) solutions and simulations were used to compare a model based on a gamma distribution of self-diffusion coefficients to more established models such as the single exponential, the stretched exponential, and the log-normal distribution model with regard to performance and consistency. Even though the gamma distribution is very similar to the log-normal distribution, its NMR signal attenuation can be written in a closed form and therefore opens up for increased computational speed. Estimates of the mean self-diffusion coefficient, the spread, and the polydispersity index that were obtained using the gamma model were in excellent agreement with estimates obtained using the log-normal model. Furthermore, we demonstrate that the gamma distribution is by far superior to the log-normal, and comparable to the two other models, in terms of computational speed. This effect is particularly striking for multi-component signal attenuation. Additionally, the gamma distribution as well as the log-normal distribution incorporates explicitly a physically plausible model for polydispersity and spread, in contrast to the single exponential and the stretched exponential. Therefore, the gamma distribution model should be preferred in many experimental situations.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
NATURVETENSKAP ->
Biologiska vetenskaper ->
Biokemi och molekylärbiologi ->
Biokemi
Nyckelord:
Pulsed-field gradient NMR, Self-diffusion, PEG, Polymer, Gamma distribution, Log-normal distribution, nuclear-magnetic-resonance, self-diffusion, integral-equations, spin-echo, water, polydispersity, cellulose
Postens nummer:
164550
Posten skapad:
2012-10-10 10:34
Posten ändrad:
2012-10-11 19:43

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