Investigation of Polymerization Mechanisms of Poly(n-Butyl Acrylate)s Generated in Different Solvents by LC−ESI−MS2

Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC−ESI−MS2) was employed for the characterization of three poly(n-butyl acrylate)s. These polymers were produced at high temperature using the same initiator, tert-butyl peroxy-3,5,5-trimethylhexanoate, but in different solvents, viz. pentyl propionate, xylene and butyl acetate. Exact mass experiments performed on these polymers in an Orbitrap instrument supplied valuable information on the end group structures. Study of the data allowed identification of many reactions during the polymerization such as beta-scission and chain transfer to solvent or radical transfer to solvent from the initiator. Different fragmentation pathways were observed from the same precursor mass on MS/MS experiments, indicating the presence of isomers. The comprehensive assignment of the peaks in the LC−MS data allowed us to describe the end group distribution in a semiquantitative way. The results clearly show that the relatively reactive solvents used for polymerization have strong influences on the polymer composition.