A Challenge on the Characterization of Poly(Styrene 4-vinylpyridine) copolymers by MALDI-TOF MS

Nitroxide-mediated controlled-radical polymeriza-tion (NMRP) is a promising technique. Poly( styrene-co-4-vinylpyridine) [P(S-4VP)] random copolymers with different molar composition were synthesized by NRMP using (2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide) (TIPNO) as a mediator. We record the MALDI-TOF spectra under various conditions. We state the conjecture (referred to as the fifty-percent conjecture) that the nitroxide is a labile bond and thus it is impossible to find MALDI conditions in which the number of intact ions is larger than one-half. The idea is to find an excep-tion. In this way, MALDI spectra allow for the determination of all end-groups, even some less-abundant ones.