Vacuum‐ultraviolet (VUV) Photo‐polymerization of Amine‐rich Thin Films from Ammonia–Hydrocarbon Gas Mixtures

Photo‐induced polymerization of hydrocarbon “monomers”, both unsaturated C2H4 and saturated CH4, has been carried out by vacuum‐ultraviolet (VUV) irradiation of the flowing gases at reduced pressure, employing near‐monochromatic radiation from Kr and Xe lamps. Using mixtures with NH3, the source of bound N in the coatings, similar concentrations, [N], can be achieved in both UV‐PE(M):N and low‐pressure plasma polymers, L‐PPE:N, but the former are much richer in primary amines, with selectivity values ([NH2]/[N]) up to 75%. UV‐PE:N and UV‐PM:N films prepared with gas mixture ratios, R, between 0.75 and 1.0 possess the main characteristics required for bio‐technological applications: (i) NH2‐rich, (ii) low loss of [NH2] upon exposure to atmosphere or water, and (iii) very low solubility in aggressive solvents, e.g., water. The VUV photo‐polymerization process, governed by reactions of free radicals from the gas‐phase, appears to result in more stable, more densely cross‐linked deposits than those from plasma‐assisted processes. magnified image