On-line fractionated size exclusion chromatography-nuclear magnetic resonance of polymers with 1H and 2H nuclear magnetic resonance detection

A new approach for on-line SEC-NMR is introduced. The method combines time slicing, fractionation with adjusted loop collection and automatic stop-flow NMR analysis. It will be called on-line fractionated SEC-NMR. This technique allows the precise determination of molar mass distributions for any polymer which can be detected by NMR. It is a significant improvement of sensitivity and accuracy compared to onflow SEC-NMR and exhibits a much easier experimental setup than off-line SEC-NMR fractionation. The new method was applied to protonated and deuterated block copolymers by using l H NMR and for the first time also H-2 NMR detection. In this case block copolymers can be correctly characterized according to their block length distributions. As the consequence very precise molar mass parameters M-n and M-w can be determined. The results of the on-line fractionated SEC-NMR are in very good agreement with the multi detector analysis. The new technique also proposes a method for separating the true copolymer and low molar mass fractions in the mixture, whose structures are confirmed by HPLC-FTIR and 2D chromatography. (C) 2012 Elsevier B.V. All rights reserved.