Mass spectra of copolymers which display compositional drifts or sequence constraints

Abstract

The spectral features appearing in mass spectra of random and block copolymers which display a drift in composition are discussed along with features appearing in mass spectra of terpolymers and tetrapolymers with sequence constraints. It is shown that previous models cannot account for these features. A new model is presented and a compact equation is derived which yields MS intensities. The prediction of the model is compared with some literature data, namely mass spectrometric data concerning a block copolymer sample containing units of alpha-methyl styrene and of methylmethacrylate which display a strong drift in composition, the molar fraction of methylmethacrylate units changing from 0.99 to 0.80 when passing from short to long macromolecular chains. The agreement between theory and experiment is good. A hyperbranched polymer obtained by condensing 4,4'-bis[p(acetoxy)phenyl] valeric acid (referred to as diphenolic acid, DPA) was then considered. The polymer turned out to be a copolymer with regular DPA units and modified DPA units (possessing a phenol group). The molar fraction of regular DPA units changes from 0.80 to 0.95 when passing from low masses to high masses. Copolymers with sequence constraints are considered, such as ABC copolymers in which AA cannot be found along the chain or ABCD copolymers in which A cannot follow A, B cannot follow B, etc. The novel method is applied to an exactly alternating copolymer with units of styrene (St) and maleic anhydride (MAH). The St-MAH sample turned out to be a complex mixture and the presence of a small amount of units of maleic acid (MAC) is detected. The abundance of MAC, estimated by the chain statistical method, is 5%. The method is applied to the copolymer obtained by reactive blending of poly(butylene terephthalate) and poly(bisphenolA carbonate). In this case, the theoretical spectra are generated and spectral features are discussed.

When medical evidence alone is simply not enough

“…We considered 60 peaks due to pentamers, hexamers, heptamers, and octamers of the type D n,m .and G n,m . The intensity of the 60 peaks was given as an input to the DROPO program49 and a minimization was launched. The result was P M‐A = 0.57, P M‐T = 0.43, P E‐A = 0.50, and P E‐T = 0.50.…”

Hyperbranched and Highly Branched Polymer Architectures—Synthetic Strategies and Major Characterization Aspects

“…Therefore information about the complete polydispersity of the hb sample cannot be achieved. In order to apply this method for hb polymers, it is again reasonable first to separate the polymer in nearly monodisperse fractions and afterward to measure them using MALDI-TOF-MS. ,,, Beautiful work has been done using the hyphenation of SEC with MALDI-TOF-MS. Jaumann et al achieved complete characterization of hb polyalkoxysiloxanes by this combination method, reaching molar mass values of more than 10 6 g/mol in the narrow distributed fractions. Montaudo also treated the topic of MALDI-TOF-MS of hyperbranched polyesters exhaustively in his work.…”

COCONUT—An Efficient Tool for Estimating Copolymer Compositions from Mass Spectra

“…MS techniques can highlight different features of polymers such as molecular weight distribution or end-groups . MS is frequently used to determine compositional drift, or the average composition, − which then can be verified by other techniques, such as nuclear magnetic resonance (NMR).…”