Excellent adhesion of electrospun nanofiber (NF) to textile support is crucial for a broad range of their bioapplications, e.g., wound dressing development. We compared the effect of several low- and atmospheric pressure plasma modifications on the adhesion between two parts of composite—polycaprolactone (PCL) nanofibrous mat (functional part) and polypropylene (PP) spunbond fabric (support). The support fabrics were modified before electrospinning by low-pressure plasma oxygen treatment or amine plasma polymer thin film or treated by atmospheric pressure plasma slit jet (PSJ) in argon or argon/nitrogen. The adhesion was evaluated by tensile test and loop test adapted for thin NF mat measurement and the trends obtained by both tests largely agreed. Although all modifications improved the adhesion significantly (at least twice for PSJ treatments), low-pressure oxygen treatment showed to be the most effective as it strengthened adhesion by a factor of six. The adhesion improvement was ascribed to the synergic effect of high treatment homogeneity with the right ratio of surface functional groups and sufficient wettability. The low-pressure modified fabric also stayed long-term hydrophilic (ten months), even though surfaces usually return to a non-wettable state (hydrophobic recovery). In contrast to XPS, highly surface-sensitive water contact angle measurement proved suitable for monitoring subtle surface changes.

Surface functionalization technologies of fibrous or porous materials are often considered relatively unstable with a shelf life of several weeks or months at most, evoked by heterogeneous treatment of their internal surface areas. Here, it is demonstrating that the fine balance of plasma etching, deposition, and oxidation involving different reactive species, strongly enhances penetration depth within complex structures. On this basis, capillary wicking is maintained over >10 years after plasma functionalization of a scaffold material used for biomedical engineering. Electrospun membranes of poly(ε‐caprolactone) are coated with an oxygen‐functional hydrocarbon layer, deposited in a competitive ablation and plasma polymerization process with CO₂ and C₂H₄ as reactive gases. Chemical analysis immediately after coating, 9 months later, and after storing at ambient conditions for over 10 years, indicate a stable surface coating. Using defined geometries such as a cavity and an undercut, the underlying plasma interaction mechanisms are revealed, showing different synergies of energetic particles, depositing species with different surface reactivities, and oxidizing species. A concerted action of such species during plasma functionalization is key to enabling long‐term wetting properties. This has a major implication for the surface functionalization of scaffolds, textiles, membranes, or foams used in diverse fields.

Long-lived free radicals in bioactive surfaces provide a highly reactive platform for direct covalent binding of biomolecules without the need for additional chemical crosslinkers. Here, we report a high concentration of long-lived free radicals (≥100 days, ∼ 1018 spin/cm3 ) measured by electron paramagnetic resonance (EPR) in amine plasma polymer thin films prepared from cyclopropylamine (CPA). The high radical density is not induced by the effect of energetic ions, but follows from the unique structure of the CPA monomer. Since the film deposition proceeds at nearly the same rate during the off-time of the pulsed plasma mode as during the on-time, and the radical density scales with on-time power rather than average power, we concluded that CPA plasma polymerization is mainly driven by biradical reactions. After the deposition, the spin density decreases steeply over the first 5 days, then levels off to about half its initial amount. A radical-kinetics model accounting only for diffusion and surface recombination successfully described the time evolution when two radicals with different diffusion coefficients were assumed. The EPR signal could be relatively well fitted with one Lorentzian function corresponding to the radicals with g-factor ∼ 2.003 (slightly varying with deposition power). However, the conclusion on the existence of two species with different diffusion coefficients motivated a refined fitting of the EPR spectra with two peaks: (i) g-factor ∼ 2.004 indicating nitrogen- or oxygen-centered radicals, stable in time, and (ii) g-factor ∼ 2.001 corresponding to a single- bonded carbon-centered radical, whose density decays with aging time.

Long-lived free radicals in bioactive surfaces provide a highly reactive platform for direct covalent binding of biomolecules without the need for additional chemical crosslinkers. Here, we report a high concentration of long-lived (≥100 days) free radicals (∼ 1018 spin/cm3, measured by electron paramagnetic resonance – EPR) in amine plasma polymer (PP) thin films prepared from cyclopropylamine (CPA), which increases with applied discharge power. After deposition, the spin density decreases steeply over the first 5 days, then levels off to about half its initial amount. A radical-kinetics model accounting only for diffusion and surface recombination successfully described the time evolution and confirmed the presence of two radical types with different diffusion coefficients. Therefore, the EPR spectra were refitted considering two peaks, resulting in the separation into two species with vastly different decay rates. One, with g-factor of 2.004, indicates a nitrogen- or oxygen-centered radical, stable in time with a lower diffusion coefficient. The other, with g-factors below 2.002, corresponds to a single-bonded carbon-centered radical, which decreases with aging time. The high radical density is not induced by the effect of energetic ions, but follows from the unique structure of the CPA monomer. Since we discovered that the film deposition proceeds at nearly the same rate during the off-time of the pulsed plasma mode as during the on-time and that the radical density scales with the on-time power rather than average power, we concluded that CPA plasma polymerization is mainly driven by biradical reactions based on Yasuda’s growth mechanism for plasma polymerization.