Industrial applications based on plasma polymerization require reliable processes that can be transferred to production‐scale reactors. To enable an inexpensive access to control plasma deposition processes, macroscopic kinetics were investigated to describe plasma polymerization, which is based on the concept of chemical quasi‐equilibrium. The evaluation of deposition rates was carried out in order to obtain the apparent activation energy for a specific process. Influencing factors, such as substrate temperature, energetic particles, reactor geometry, plasma expansion, pressure, monomer, carrier/reactive gas, power modulation, and plasma source were thoroughly examined. The obtained activation energy was correlated to the plasma‐chemical processes, such as dissociation and radical formation, which are taking place within the active plasma zone. Since these processes are also contributing to the film growth, the activation energy was used for the scale‐up of plasma polymerization processes.

Summary: In plasma polymerization often additional, non‐polymerizable gases are used, either as carrier gas or as reactive co‐monomer. The gas ratio represents an additional parameter, which complicates the understanding of plasma polymerization processes. Therefore, we thoroughly investigated the deposition rates of different gas mixtures (O2/HMDSO, N2 and NH3/CxHy, as well as inert gas/CxHy) on the basis of a macroscopic approach. Since the mass deposition rates depend on the specific energy W/F, the plasma polymerization regime for the corresponding polymerizable monomer can be identified by introduction of a modified flow F = Fm + a Fc (sum of monomer flow Fm and carrier gas flow Fc with a flow factor a). Any deviations discovered during application of this novel approach indicate additional effects, such as ion‐induced effects.

No abstract

The plasma‐assisted process presented in this paper facilitates the deposition of nitrogen containing functional coatings on textiles. Low pressure RF plasma was used to deposit multi‐functional thin films, which have a high amine content. Either acetylene or ethylene were mixed with ammonia to obtain a crosslinked structure that contained functional groups, which were accessible for dye molecules throughout the film volume. Varying deposition conditions were used in order to compare hydrocarbon gas mixtures in terms of deposition rates, water contact angles, aging, dyeability, yellowness index, and rub/wash fastnesses. The deposition rates were found to be higher for the acetylene discharges, but decreased with increasing ammonia‐to‐hydrocarbon ratios for both gas mixtures. Although this indicates etching effects, a permanent hydrophilization could still be obtained. These findings demonstrate that plasma polymerization provides an eco‐friendly multi‐functionalized surface modification, since the use of chemicals, waste water etc. can be eliminated. Dyeing of the plasma coatings by acid dyestuffs showed that the relative color strength value, i.e. amine functionalities, can be noticeably enhanced, while being strongly influenced by the energy input and by the gas ratio. It was evident that the coating quality could be improved significantly using an ammonia/ethylene plasma due to reduced unsaturated bonds, the latter being investigated by the CIELAB color spaces. A high dyeing fastness indicated a strong dye‐molecule bonding, which in turn, is an indication of permanency of the amine groups. A pilot‐scale web coater at Empa was used to demonstrate the feasibility of industrial scale‐up.

Background In January 2022, United States guidelines shifted to recommend isolation for 5 days from symptom onset, followed by 5 days of mask wearing. However, viral dynamics and variant and vaccination impact on culture conversion are largely unknown. Methods We conducted a longitudinal study on a university campus, collecting daily anterior nasal swabs for at least 10 days for RT-PCR and culture, with antigen rapid diagnostic testing (RDT) on a subset. We compared culture positivity beyond day 5, time to culture conversion, and cycle threshold trend when calculated from diagnostic test, from symptom onset, by SARS-CoV-2 variant, and by vaccination status. We evaluated sensitivity and specificity of RDT on days 4-6 compared to culture. Results Among 92 SARS-CoV-2 RT-PCR positive participants, all completed the initial vaccine series, 17 (18.5%) were infected with Delta and 75 (81.5%) with Omicron. Seventeen percent of participants had positive cultures beyond day 5 from symptom onset with the latest on day 12. There was no difference in time to culture conversion by variant or vaccination status. For 14 sub-study participants, sensitivity and specificity of day 4-6 RDT were 100% and 86% respectively. Conclusions The majority of our Delta- and Omicron-infected cohort culture-converted by day 6, with no further impact of booster vaccination on sterilization or cycle threshold decay. We found that rapid antigen testing may provide reassurance of lack of infectiousness, though guidance to mask for days 6-10 is supported by our finding that 17% of participants remained culture positive after isolation.