Some Remarks on Chemical Derivatization of Polymer Surfaces after Exposure to Nitrogen‐Containing Plasmas

Abstract

In this paper some basic assumptions underlying the chemical derivatization analysis of polymer surfaces treated in nitrogen‐containing plasmas are critically examined. Imines, which are known to represent major constituents of such surfaces as well as of plasma polymers grown from amine precursors, show a very versatile chemical reactivity. For example, imines are generally able to exchange their carbonyl component with aromatic aldehydes. Therefore, surface reactivity of polymers treated in nitrogen‐containing plasmas with 4‐trifluoromethyl‐benzaldehyde (TFBA) or other benzaldehydes appears to be attributable not only to (primary) amines. Similar conclusions must be drawn for several other derivatization reagents.

Challenges in the characterization of plasma polymers using XPS

“…Klages et al [120] and Ruiz et al [121], however, underline that derivatization is not a trivial and easy method, and that in some cases, a distinction between primary, secondary amines or hydroxyl groups is not obvious due to a lack of specificity of the derivatization agents and necessitates calculations. Klages et al even suggest that, due to the presence of imines (randomly generated during plasma polymerization), the derivatization of primary amines on plasma-deposited coatings will always present uncertainties, due to the poor selectivity with respect to imines [120].…”

“…Klages et al even suggest that, due to the presence of imines (randomly generated during plasma polymerization), the derivatization of primary amines on plasma-deposited coatings will always present uncertainties, due to the poor selectivity with respect to imines [120].…”

Tuning the Surface Properties of Oxygen-Rich and Nitrogen-Rich Plasma Polymers: Functional Groups and Surface Charge

“…Recently published work has shown that secondary reactions of TFBA with other functional groups, such as, imines were possible and that therefore, the derivatization results can be considered as a general measure of nucleophilic reactivity rather than an evaluation of primary amines [37]. However, surface charge results presented show that a significant portion of the N groups present on the surface induce a surface charge in physiological pH and the assumption that a significant portion of the derivatized groups are likely to be amines is reasonable.…”

Nitrogen Plasma Modification and Chemical Derivatization of Polyethylene Surfaces – An In Situ Study Using FTIR‐ATR Spectroscopy

“…The interpretation of the bands in the 1 550 to 1 700 cm −1 region is complicated by the unsaturation of carbon–carbon bonds occurring along with the formation of N‐containing unsaturated functional groups CN and possibly carbonyl. As already noted in a previous paper, imine groups may play a bigger role on polymer surfaces plasma‐treated in nitrogen atmospheres than frequently thought and – aside from reactions leading to an incorporation of nitrogen within functional groups, also the formation of CC double bonds by the interaction of nitrogen atoms with alkyl radicals is probably a favorable reaction channel. In case of ethyl‐D 5 radicals in the gas phase the deuterium abstraction by nitrogen atoms, which could be considered as a model reaction for the interaction of a radical center at the polyethylene chain with atomic N, accounts for nearly two‐thirds of the radicals reacted while the formation of an iminyl radical and a methyl radical accounts for most of the rest …”

“…We showed that this assumption cannot be maintained, however, in situations where the presence of other moieties such as imino groups cannot be disregarded. Although imines have long been known to be formed on polymer surfaces exposed to nitrogen plasmas, their reaction abilities during chemical derivatization have generally been ignored …”