TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: (I) is administered with another compound that has the capability to modify and/or be incorporated into the coating forming material and/or the resultant deposited coating. The plasma is pulsed according to a pulsing regime which changes in a controlled manner throughout the course of a single coating deposition. The anhydride coating formed is subsequently modified by hydrolysis, aminolysis, esterifcation or acylation of the anhydride groups. (I) and/or the further monomer or gas is introduced into the excitation medium in the form of atomized liquid droplets. In the method, at least one of a chamber containing the excitation medium, the substrate, (I) and other compound is heated. The application of the anhydride coating occurs at atmospheric pressure. Preferred Components: (I) comprises: a substituted anhydride compound of formula (R1-C(=O)-O-C(=O)-R2) (IA); and maleic anhydride compound of formula (II), preferably maleic anhydride, itaconic anhydride or (trifluoromethyl)maleic anhydride. The another compound is: inert; not incorporated within the anhydride coating; reactive gas or a further monomer; a further monomer which is an organic monomer; and delivered in a pulsed manner. The monomer is a perfluorinated 1-10C alkane or a perfluorinated aryl compound. The excitation medium comprises pulsed plasma. The coating has a proton conductivity of greater than or equal to 70 mS/cm, preferably 100 mS/cm. The excitation medium comprises continuous wave or pulsed electrical discharges, thermal chemical vapor deposition, initiated chemical vapor deposition, photodeposition, e-beam curing, ion-beam curing, and target sputtering. The substrate is a solid, particulate, permeable and porous substrate.Either R1, R2 = hydrocarbyl that carry an electron-withdrawing or electron donating substituent; orR1+R2 = optionally unsaturated 3-8C chain that optionally carries at least one electron withdrawing or electron donating substituent;dotted bond = either single or double bond; andR3, R4 = H or electron-withdrawing group, preferably methylene or trifluoromethyl, provided that at least one of the groups is an electron withdrawing group.