Methylation of acidic moieties in poly(methyl methacrylate‐co‐methacrylic acid) copolymers for end‐group characterization by tandem mass spectrometry

Abstract

The complete structural characterization of a copolymer composed of methacrylic acid (MAA) and methyl methacrylate (MMA) units was achieved using tandem mass spectrometry. In a first step, collision-induced dissociation (CID) of sodiated MAA-MMA co-oligomers allowed us to determine the co-monomeric composition, the random nature of the copolymer and the sum of the end-group masses. However, dissociation reactions of MAA-based molecules mainly involve the acidic pendant groups, precluding individual characterization of the end groups. Therefore, methylation of all the acrylic acid moieties was performed to transform the MAA-MMA copolymer into a PMMA homopolymer, for which CID mainly proceeds via backbone cleavages. Using trimethylsilyldiazomethane as a derivatization agent, this methylation reaction was shown to be complete without affecting the end groups. Using fragmentation rules established for PMMA polymers together with accurate mass measurements of the product ions and knowledge of reagents used for the studied copolymer synthesis, a structure could be proposed for both end groups and it was found to be consistent with signals obtained in nuclear magnetic resonance spectra.

End‐group characterization of poly(styrene sulfonate sodium salt) by activated electron photo‐detachment dissociation

“…For example, the CID of PMAA was shown to mainly consist of successive eliminations of water molecule between two acidic pendant groups . Since similar results were obtained in positive ion mode, a sample pretreatment should first be implemented to enable PMAA end‐group characterization in positive mode CID experiments . It consists of methylating all acrylic acid moieties to transform PMAA into a PMMA polymer, for which collisional activation induces backbone cleavages .…”

“…[18] Since similar results were obtained in positive ion mode, [19] a sample pretreatment should first be implemented to enable PMAA end-group characterization in positive mode CID experiments. [20] It consists of methylating all acrylic acid moieties to transform PMAA into a PMMA polymer, for which collisional activation induces backbone cleavages. [17,[21][22][23][24] Similarly, CID of negatively charged PSS was recently reported to generate either product ions containing both end-groups or internal fragments.…”

Mehrdimensionale Massenspektrometrie von synthetischen Polymeren und modernen Materialien

“…Daran schließt sich eine zweite Stufe der Massenanalyse zur Bestimmung der m / z ‐Werte der Fragment‐Ionen an. Solche Experimente zeigen einzelne Polymerendgruppen auf; dagegen gibt das eindimensionale MS‐Spektrum Aufschluss über die Summe der in dem Oligomer an den Kettenenden vorliegenden Substituenten, die auch eine oder mehrere unvollständige oder komplette Monomereinheiten enthalten können. Darüber hinaus kann die MS/MS eingesetzt werden, um Copolymersequenzen zu analysieren und Polymerstrukturen zu differenzieren, wie das in den Abschnitten 2.1 und 2.2 mit ausgewählten Beispielen veranschaulicht wird.…”

Preparation of acid‐cleavable branched polymers for argon fluoride photoresists via reversible addition–fragmentation chain‐transfer polymerization

“…For GPC measurement, the carboxylic acid groups derived from EAdMA and DMHDMA were methylated as follows. [22][23][24] The hydrolyzed polymer was dissolved in a mixture of THF (10.0 mL) and MeOH (3.00 mL) in a 100-mL, round-bottom flask equipped with a stirring bar. Then, 1.00 mL of a diethyl ether solution of trimethylsilyl diazomethane (2.0M) was added to the solution.…”