## 2 Experimental Details  
### Materials and Methods  
The pulsed DBD plasma was generated at atmospheric pressure in a chemical reactor with a plane-parallel configuration as presented in Figure 1. High-voltage monopolar pulses were applied between two electrodes with circular geometry (30 mm in diameter) placed 5 mm from each other. A 1 mm thick glass layer covering both electrodes was used as dielectric barrier. A similar DBD configuration was employed in our earlier published research [19; 21; 22].  
In a DBD glow operational mode, two characteristic current peaks (Figure 2a) are associated with each applied voltage pulse to describe the occurrence of the primary (1 ry) and secondary (2 ry) plasma discharges [23; 24; 25]. The experiments were made at room temperature in a laminar flowing of high-purity helium gas (99.999%), with a flow rate of 3 L/min. No preliminary vacuum pumping was used. Prior to the experiment, the working gas was blown into the reactor chamber for 5 min to remove air impurities. Then, the ethylene glycol monomer vapors were introduced at a consumption rate of 16 mL/min by using an additional helium flow rate of 0.5 L/min for monomer bubbling. The ethylene glycol monomer of 99.0% purity was purchased from Merck-Chemical.  
The amplitude of the applied discharge pulse was maintained constant at 4.5 kV, while the repetition rate was varied between 2 kHz and 10 kHz. All studies were conducted with a constant polymerization time of 10 min. The asprepared pp-PEG films were characterized by the Fourier transform infrared spectroscopy (FTIR) (Nicolet Nexus FT-IR  
Figure 1: Experimental arrangement of the pulsed DBD plasma generated at atmospheric pressure in He or He/ethylene glycol vapor mixture used for the fabrication of porous pp-PEG films.  
Figure 2: (**a**) Temporal profile of the applied voltage with generated electrical current during DBD. (**b**) 30 ns gated ICCD spectrally integrated images of the primary (Iry) and secondary (2 ry) DBD plasma expanding in He. The inserted sketch shows the placement of the discharge electrodes, where GR represents the ground electrode and HV represents the high-voltage electrode.  
spectrometer, Thermo Fisher Scientific, Waltham, MA, USA), scanning electron microscopy (SEM) (Quanta 200 Scanning Electron Microscope FEI Company, Hillsboro, OR, USA) and liquid-phase chromatography (HPLC) techniques (Waters 2695 separation module, Waters Micromass, Quattro Micro mass spectrometer equipped with ESI-Electrospray Ionization, Wythenshawe, Manchester, UK).  
Intensified charge-coupled device (ICCD) fast imaging technique is very often used to study transitory processes that occur in plasma laboratory sources [26; 27; 28]. By means of this method, the evolution of the global plasma emission was recorded (Figure 2b). Each image was normalized to the recorded maximum intensity emitted by the plasma to observe the evolution of the plasma along the current pulse width. The measurements were done with ICCD camera produced by Hamamatsu Photonics, Hamamatsu, Japan (C8484-05G) that allows optical measurements in the spectral range between 300 and 1000 nm, with a maximum sensitivity between 350 and 800 nm. The DBD plasma was monitored during 25 \(\upmu\)s pulse discharge length by using an additional rectangular signal of 30 ns width. This signal was triggered by the discharge current pulse, either the positive rising edge or the negative dropping edge, depending on the plasma region that is being investigated. The applied signal forces the camera to remain open only for the duration of the gate. By moving the gate at a different delay from the fixed discharge current peaks, either compared to that of the positive or negative current peaks, 30 ns gated ICCD fast images were recorded during the primary or secondary discharge, respectively.