Unraveling the architecture of plasma polymers by electrospray tandem mass spectrometry

• An analytical methodology is proposed to analyze insoluble plasma polymers by ESI-MS.
• Plasma polymerized HMDSO is degraded into PDMS chains under controlled ethanolysis.
• Standards with well-chosen end-groups are submitted to CID to compile diagnostic ions.
• Terminations of the solubilized chains are deduced based on the MS/MS of standards.
• The architecture of the network is unraveled from the structure of the soluble chains.

This feature article presents the implementation of a controlled chemical degradation (namely ethanolysis) combined with electrospray tandem mass spectrometry (ESI-MS/MS) as an original analytical strategy to gain insights into the molecular composition of insoluble plasma polymers deposited from hexamethyldisiloxane (HMDSO). Dissociation rules were established for poly(dimethylsiloxane) standards (PDMS) holding trimethylsilyl and/or hydroxy and/or ethoxy end-groups, expected to be found as ethanolysis products released after the cleavage of bonds specifically at cross-linking points of the solid plasma polymer network. Mechanistic investigations were performed on the collision-induced decomposition (CID) of ammonium adducts of the selected standards to derive diagnostic ions typical of a given chain termination. Based on the so-listed diagnostic MS/MS features, the MS/MS analysis of the ethanolyzed samples allowed their structures to be deduced and the architecture of the original plasma polymers to be reconstructed.

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