Electron activation of dyes in vacuum with their polymerisation during film growth

Abstract This research presents an integrated experimental and simulation-based study on the activation of allyl-terminated dyes using low-temperature plasma (LTP). Thin films of polymethine and heteroazulene compounds containing a terminal allyl group (allyl-terminated compounds, ATC) were produced via physical vapor deposition (PVD) under vacuum conditions. In situ optical spectra recorded during the deposition process confirmed the absence of decomposition products, indicating that the ATC molecules remain intact during growth. Atomic force microscopy (AFM) was employed to determine the influence of 3D molecular topology and chemical structure of the ATC on the resulting film morphology. To induce polymerization, the allyl groups were activated by gas-phase electrons using three distinct variants of LTP. The results indicate that the most stable and smooth films are achieved through electron activation (eA) combined with low-pressure LTP (eA+LTP). Furthermore, simulations were utilized to model the aggregation of neutral ATC molecules during PVD, as well as the specific changes in electronic structure occurring upon electron attachment. Based on these findings, an anionic polymerization mechanism is proposed.