Molecular weight determination of block copolymers by pulsed gradient spin echo NMR.
Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) is the technique of choice to achieve molecular weight data for synthetic polymers. Because the success of a MALDI-MS analysis critically depends on a proper matrix and cation selection, which in turn relates closely to the polymer chemical nature and size, prior estimation of the polymer size range strongly helps in rationalizing MALDI sample preparation. We recently showed how pulsed gradient spin echo (PGSE) nuclear magnetic resonance could be used as an advantageous alternative to size exclusion chromatography, to rationalize MALDI sample preparation and confidently interpret MALDI mass spectra for homopolymers. Our aim here is to extend this methodology to the demanding case of amphiphilic block copolymers, for which obtaining prior estimates on the Mw values appears as an even more stringent prerequisite. Specifically, by studying poly(ethylene oxide) polystyrene block copolymers of distinct molecular weights and relative block weight fractions, we show how PGSE data can be used to derive the block Mw values. In contrast to homopolymers, such determination requires not only properly recorded calibration curves for each of the polymers constituting the block copolymers but also an appropriate hydrodynamic model to correctly interpret the diffusion data.
Barrère
Caroline
C
Laboratoire Chimie Provence, Spectrométries Appliquées a la Chimie Structurale, Universités Aix-Marseille I, II & III-CNRS, UMR 6264, F-13397 Marseille Cedex 20, France.
Mazarin
Michaël
M
Giordanengo
Rémi
R
Phan
Trang N T
TN
Thévand
André
A
Viel
Stéphane
S
Charles
Laurence
L
D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
D011108:Polymers