Successful MALDI mass spectrometry of poly(4-vinylpyridine) using a solvent-free sample preparation

• Successful MALDI-MS of poly(4-vinylpyridine) has been achieved for the first time.
• Solvent-free sample preparation allowed Mw determination for P4VP up to 40 kDa.
• High accessibility of nitrogen atoms was evidenced to promote deleterious matrix adducts.
• Accuracy of MALDI-MS data was validated by SEC and diffusion NMR.

The position of nitrogen atoms in poly(4-vinylpyridine) (P4VP), compared to their poly(2-vinylpyridine) (P2VP) isomers, explains most difficulties faced when determining their molecular weight parameters by size exclusion chromatography, due to oligomers strongly adsorbing onto stationary phases. The high accessibility of these nitrogen atoms is shown here to be challenging also in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), probably accounting for the lack of mass data reported for P4VP in the literature. Using a “bottom-up” strategy starting from small oligomers prior to consider high molecular weight polymers, P4VP species were observed here to strongly interact with acidic matrix molecules such as 2,5-DHB when preparing MALDI sample using the traditional dried-droplet procedure. In contrast, MALDI best performed when using a solvent-free sample preparation involving a non-acidic matrix such as DCTB. Accordingly, reliable MS determination of molecular weight parameters could be achieved for P4VP up to about 40 kDa, as validated by diffusion NMR experiments.

Figure optionsDownload high-quality image (137 K)Download as PowerPoint slide