1：Experimental Design and Method Selection:

The study used time-resolved in situ mass spectrometry to analyze pulsed plasma polymerisation of HFPO. Electron-impact and electron-attachment ionization modes were employed to monitor neutral and ionic species, with time-resolved detection during on and off periods of the plasma duty cycle.

2：Sample Selection and Data Sources:

HFPO gas precursor (+98%, Aldrich Chemical Company Inc.) was used at a pressure of 0.2 mbar. Reference perfluorocarbon molecules (perfluoro-n-pentane and perfluoro(methylcyclohexane)) were analyzed for mass fragmentation patterns.

3：2 mbar. Reference perfluorocarbon molecules (perfluoro-n-pentane and perfluoro(methylcyclohexane)) were analyzed for mass fragmentation patterns. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Cylindrical glass reactor (8.5 cm diameter, 2943 cm3 volume), turbomolecular drag pump (model TPD 022, Pfeiffer Vacuum Technology AG), diaphragm pump (model N813.4 ANE, KNF Neuberger GmbH), RF power supply (model RFG 600SE, Coaxial Power Systems Ltd), pulse signal generator (model TG503 5 MHz pulse, Thurlby Thandar Instruments Ltd), oscilloscope (model OX 530 20 MHz, Metrix Ltd), mass spectrometer (model HAL EQP 2500 Hiden Analytical Ltd), turbomolecular pump (model TMU 260, Pfeiffer Vacuum Technology AG), rotary vane pump (model DUO 2.5, Pfeiffer Vacuum Technology AG), fine control needle valve (model 145–217–4P4PC, Meggitt Avionics Ltd).

4：5 cm diameter, 2943 cm3 volume), turbomolecular drag pump (model TPD 022, Pfeiffer Vacuum Technology AG), diaphragm pump (model N4 ANE, KNF Neuberger GmbH), RF power supply (model RFG 600SE, Coaxial Power Systems Ltd), pulse signal generator (model TG503 5 MHz pulse, Thurlby Thandar Instruments Ltd), oscilloscope (model OX 530 20 MHz, Metrix Ltd), mass spectrometer (model HAL EQP 2500 Hiden Analytical Ltd), turbomolecular pump (model TMU 260, Pfeiffer Vacuum Technology AG), rotary vane pump (model DUO 5, Pfeiffer Vacuum Technology AG), fine control needle valve (model 145–217–4P4PC, Meggitt Avionics Ltd). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The chamber was cleaned with oxygen plasma, purged with HFPO, and pulsed plasmas were ignited with fixed off-period (500 ms) and variable on-periods (10, 5, 2 ms) at 50 W power. Mass spectrometry was performed in time-averaged and time-resolved modes, with signal gating for specific time windows.

5：Data Analysis Methods:

Mass spectra were averaged over multiple pulse cycles, and data were compared to NIST database for fragmentation patterns. Signal intensities were analyzed to infer species concentrations and reaction mechanisms.