## 4 Discussion
Although non-sticky coatings were deposited at LP with 0.5 sccm of DEGDME in the gas mixture, these coatings, when deposited at the lowest input power values investigated (i.e., 5 W) needed for low fragmentation and high retention of the structure of the monomer, poor stability in water was recorded, as reported in Table S1, thus attesting once again the need of more energetic conditions for a tight bond to the substrate and more cross-linking. However, increasing the input power from 5 to 50 W, by following strategy 1 of Figure 1, decreases the COC and increases the carbonyl contribution (Figure 3a) in coatings deposited from only DEGDME. The rearrangement of ethers and their conversion into carbonyl groups probably occur due to the high density of radicals produced at high input power values needed for low fragmentation and high retention of the structure of the monomer, poor stability in water was recorded, as reported in Table S1, thus attesting once again the need of more energetic conditions for a tight bond to the substrate and more cross-linking. At present, many research groups are developing cold AP plasma processes and reactors to conduct plasma polymerization processes of PEO-like coatings [16; 34]. Many different types of AP plasma reactors are being developed, e.g., DBD reactors with various electrode configurations (e.g., classical parallel-plate geometries, surface DBD, etc.) plasma jets, and torches. These are suitable candidates for replacing traditional coating techniques, due to their simple scalability, and limited need of vacuum pumps. The control over the plasma polymerized film properties has improved greatly in the last few years; nevertheless, often hydrophilic films on hydrophobic surfaces can undergo delamination in water media when deposited in AP plasma conditions [34]. Moreover, a higher monomer structure retention is generally expected in AP plasmas with respect to LP ones, particularly when the monomer is injected in form of an aerosol. The deposition of PEO-like coatings, in aerosol, assisted DBD, produces rough coatings in our experimental conditions, probably due to the contribution of aerosol droplets to the polymerization or deposition of the monomer vapors that can lead to the formation of aggregates. [35; 36]. [PERSON] et al. [37] deposited PEO-like coatings on Si wafer surface using TEGDME and diethylene glycol vinyl ether monomers in a non-equilibrium AP plasma jet and reported the formation of particulate in the process as a result of a high degree of polymerization. Further experiments are necessary to assess the mechanism of formation of these micro-nano-structures, as that is far from the aim of this paper. The results reported in Figure 11 clearly show that the PEO-like coatings deposited at lower carrier flow (higher TEGDME concentration in the discharge) had higher percentages of PEO-like CH\({}_{2}\)CH\({}_{2}\)O moieties, whatever the applied voltages investigated, similar to those obtained in LP conditions. By contrast, at a higher carrier gas flow rate, the precursor molecules underwent greater fragmentation, likely due to the higher density of He active species, which provide sufficient energy to break most chemical bonds in monomer, resulting in increased cross-linking and lower PEO-character of the deposited coating. These results are similar to those obtained when high input power is used in LP processes. It has been demonstrated by XPS that the PEOA and PEOB coatings with different PEO-character are stable after 3 days of double distilled water soaking when deposited in a single step process but, during cell culture experiments, they delaminate to a certain extent. Since the detachment was constantly observed after 4-5 h of cell-culture and no detachment was observed during the water stability tests described previously, we attribute this effect to the pulling force exerted by the adhering cells on the coatings during the early time of growth. This effect was already observed in [38] on conventional PEO polymers.