1H DOSY NMR determination of the molecular weight and the solution properties of Poly(N-acryloylmorpholine) in various solvents

International audience1H DOSY NMR provides a simple and convenient method to determine both the molecular weight and the solution properties of poly(N-acryloylmorpholine) (PNAM) in various organic and aqueous solvents. This technique is used to measure the average diffusion coefficient DPNAM of a library of PNAM samples of increasing molecular weights synthesized by reversible addition fragmentation chain transfer controlled radical polymerization. In all solvents, the highly linear relationship between Log DPNAM and Log Mw yields calibration curves that can be used for the reliable determination of the molecular weight of various types of PNAM samples. In addition, the slope of the calibration curves can be considered as the Flory exponent δ characterizing the solvent–polymer interaction. The measurements show that CDCl3 and D2O are theta solvents for PNAM and that δ slightly decreases in phosphate buffer solution (PBS), pH 7.4, and upon addition of MeOD in D2O