Scaling exponent and dispersity of polymers in solution by diffusion NMR

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:493

Article

Williamson, Nathan H.¹  Roding, Magnus^2,3  Miklavcic, Stanley J.⁴  Nyden, Magnus^1,3 

[1] Univ South Australia, Future Ind Inst, Mawson Lakes, SA 5095, Australia

[2] SP Agrifood & Biosci, Frans Perssons Vag 6, S-40229 Gothenburg, Sweden

[3] Univ Coll London, Sch Energy & Resources, 220 Victoria Sq, Adelaide, SA 5000, Australia

[4] Univ South Australia, Phen & Bioinformat Res Ctr, Sch Informat Technol & Math Sci, Mawson Lakes, SA 5095, Australia

关键词: Pulsed gradient spin echo;    Pulsed field gradient;    Nuclear Magnetic Resonance spectroscopy;    Molecular weight distribution;    Polymers;    DOSY;    Polydispersity Index;    Self-diffusion;    Molar mass;    Flory exponent;    Lognormal distribution;    Gamma distribution;    End-group analysis;    Scaling law;   

DOI  :  10.1016/j.jcis.2017.01.058

来源: Elsevier

【 摘 要 】

Molecular mass distribution measurements by pulsed gradient spin echo nuclear magnetic resonance (PGSE NMR) spectroscopy currently require prior knowledge of scaling parameters to convert from polymer self-diffusion coefficient to molecular mass. Reversing the problem, we utilize the scaling relation as prior knowledge to uncover the scaling exponent from within the PGSE data. Thus, the scaling exponent a measure of polymer conformation and solvent quality and the dispersity (Mw/M) are obtainable from one simple PGSE experiment. The method utilizes constraints and parametric distribution models in a two-step fitting routine involving first the mass-weighted signal and second the number-weighted signal. The method is developed using lognormal and gamma distribution models and tested on experimental PGSE attenuation of the terminal methylene signal and on the sum of all methylene signals of polyethylene glycol in D(2)0. Scaling exponent and dispersity estimates agree with known values in the majority of instances, leading to the potential application of the method to polymers for which characterization is not possible with alternative techniques. (C) 2017 Elsevier Inc. All rights reserved.

【 授权许可】

Free