Year: 2026
Type: preprint
Abstract: The early-stage dimer formation of 1,3-benzoxazine (PH-a) was investigated as a diagnostic system for understanding the ring-opening polymerization (ROP) mechanism using a coupled FAIMS-IRMPD-MS/MS platform. High-field asymmetric waveform ion mobility spectrometry (FAIMS) resolved the protonated PH-a dimer into three distinct populations. A series of methyl-blocked benzoxazine derivatives was used to systematically eliminate individual reactive sites and assign each FAIMS population to a specific reaction route via tandem MS fragmentation patterns and IRMPD action spectroscopy, supported by theoretical vibrational spectra obtained by DFT calculations. Four dimer formation pathways were confirmed: phenolic aromatic substitution at the ortho and para positions, and arylamine aromatic substitution at the ortho and para positions of the aniline ring. Phenoxy- and nitrogen-mediated attack routes were not observed. Each pathway yields dimers in either a closed-ring (CRB) or open-ring (ROP) form, a structural duality with direct implications for the crosslinking topology and network heterogeneity of the resulting polybenzoxazine.
Source: ChemRxiv
Institution: Universidade de São Paulo
Language: English
Subfield: Spectroscopy
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Awards: G2859144839, G5609570957
OpenAlex ID: W7221134988