Past research in this laboratory has focused on the deposition of nitrogen- (N)-rich thin organic coatings for biomedical applications; among usual fabrication methods are plasma polymerization (PP) at low- ("L") or atmospheric- (high-, "H")-pressure. In the "L" case, ethylene ("E", C2H4)/ammonia (NH3) feed-gas mixtures with different flow ratios, R, are used, by which the nitrogen- and primary amine concentrations, [N] and [-NH2], respectively, can be reproducibly controlled. The generic symbol we use for that family of deposits is L-PPE:N. In the present research, we used acetylene ("A", C2H2) as the hydrocarbon feed, because our earlier experience with "H"-type materials (H-PPE:N and H-PPA:N) revealed striking differences in physico-chemical (e.g. [N] and [-NH2], and solubility) characteristics, which are important for applications. We now find that such differences also exist between the L-PPA:N and L-PPE:N families of coatings. This is attributed to the fundamentally different bonding structures of "A" and "E", namely CHa parts per thousand CH and CH2=CH2; the former leads to more highly cross-linked, [NH2]-leaner deposits, as was also noted for the "H"-type deposits mentioned above.