Conformation effects on the dissociation of ionized polymers

The collision-induced dissociation (CID) of a series of oligomer chain lengths of four polymer samples have been quantified according to their observed total relative fragment ion abundances. The CID mass spectra of oligomers of ionized poly(methyl methaerylate) (PMMA), with three different types of end groups and polystyrene (PS), were obtained at fixed center-of-mass collision energies and collision numbers. For the PMMA polymers, the total fragment ion abundance increases with increasing chain length, consistent with an increase in internal energy deposition with the size of the ion. A discontinuity in the increase in total fragment ion abundance appears to correspond with a change in conformation of the polymer ions from linear (at short chain lengths) to cyclic (at long chain lengths). Ionized PS does not exhibit this change in conformation as all chain lengths show compact structures and accordingly the total fragment ion abundance does not change with increasing chain length.