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

Abstract

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.

Interfacing Multistage Mass Spectrometry with Liquid Chromatography or Ion Mobility Separation for Synthetic Polymer Analysis

“…[31][32][33]40,72 Applications of adsorption-mode LC (interactive LC) have only begun recently. 33,39,41,42,73,74 Similarly, IM-MS is an emerging method in the characterization of polymers. Studies reported in the last years have demonstrated that ion mobility separations can resolve complicated polymer and material distributions arising from different end groups, varied structural arrangements, unpredicted byproducts or degradation products.…”

Photo-initiated copolymerization of allyl and vinyl ethers with dialkyl fumarates: A mechanistic investigation by ESI mass spectrometry

“…In addition, b-scission and transfer reactions are frequently reported to take place in the absence [26] or in the presence of a chain transfer agent [27], to the solvent, to the monomer [28] or to the polymer [29]. MALDI-TOF-MS has been used not only to investigate propagation [30], but for evidencing irreversible termination in controlled free-radical polymerization [31].…”

High‐Resolution Ion Mobility Spectrometry–Mass Spectrometry on Poly(methyl methacrylate)

“…Although the abundance of the high‐molecular weight components in the PMMA is relatively low, IMS‐MS is still capable of the analysis. Compared to the LC‐MS work on poly( n‐ butyl acrylate)s (PBAs) of comparable average molecular weight ( M n of 3800 Da) reported elsewhere,7f in which components were only observed up to 2000 Da, IMS‐MS can be used independently for the detailed investigation of the entire MWD of the PMMA sample.…”

“…The elemental compositions of the endgroups appearing in the polymer series were identified using a linear regression method 8. The naming system used here is similar to that used in previous reports,7a,f that is, the series are named after their endgroup composition (Figure 2, [‐H] indicating an unsaturated endgroup resulting from disproportionation.) The most intense series of peaks sh (or mh, which is one degree of polymerization (DP) higher than sh, but has the same elemental composition and therefore has the same mass as sh), m / z 439 + ( n −3)×100, contains a butyl acetate endgroup (or methyl) at one end of the chain and is terminated with a H‐abstracted endgroup at the other end.…”

“…The first peak ( m / z 737.3748) is attributed to sh* or mh* and the second peak ( m / z 737.4481) is attributed to rh. It is very likely that both mh* and sh* are present because both endgroups were observed by LC‐Orbitrap MS in a PBA sample that was prepared under similar polymerization conditions 7f. This small exact mass difference would not be detected in a low‐resolution mass spectrometer, resulting in a single, unresolved peak with m / z 737.4.…”