The production of chemically‐defined plasma polymers and the introduction of monotype functional groups onto polymer surfaces are described. One method is to lower the energetic level of low‐pressure plasmas. Pressure‐ and plasma‐pulsed plasmas were successfully tested for the production of chemically‐defined plasma polymers by increasing the monomer supply during the plasma‐off period. Well‐defined ultra‐thin polymer films with regular structure were deposited from atmospheric plasmas by electrospray techniques. Post‐plasma wet‐chemical processing was also applied, as were gas/liquid‐based aerosols and underwater plasmas.magnified image

Underwater plasma and glow discharge electrolysis are interesting new methods for polymer surface functionalization. The achievable content of O‐containing functional groups exceeds that of oxygen glow discharge gas plasmas by a factor of two (up to ca. 56 O/100 C). The percentage of OH groups among all O‐containing groups can reach 25 to 40%, whereas it is about 10% in the gas plasmas. Addition of hydrogen peroxide increases the fraction of OH groups to at most 70% (27 OH/100 C). The liquid plasma systems are also able to polymerize acrylic acid and deposit the polymer as very thin film on substrate surfaces or membranes, thereby retaining about 80% of all COOH functional groups (27 COOH/100 C).

Among new types of plasma processes, the underwater plasma is one of the most attractive methods for functionalization of polymer surfaces. The interesting features of plasma solution system are that the material surfaces to be modified remain in contact with the plasma‐moderated solution. The role of plasma‐moderated liquids, allows the reach of the reactive species through solution onto the geometrically hindered sites. The UV radiation produced in plasma formation helps in generating additional excited, ionized, and dissociated molecules and species in the reaction solution. An interesting feature of the technique is its flexibility to use a wide variety of additives as or in solution system. This allows us to create a selective or monotype functionalization of material surfaces. Such system was studied for the selective hydroxyl functionalization of polypropylene surface. The oxidation of polymer surfaces and the introduction of O‐containing functional groups by underwater plasma was found to exceed concentrations typically achieved in oxygen low‐pressure gas discharge plasmas up‐to two‐folds (maximal 56 O/100 C). The fraction of OH groups among all O‐containing moieties amounts from 25 to 40% in comparison to that in the gas plasma of about 10% OH groups. Addition of hydrogen peroxide into this same system increases the fraction of CO bonds up to 75% (27‐OH/100 O). A study was focused to optimize the role of hydrogen peroxide on the efficiency of oxidation and selectivity with chemical derivatization with respect to the formation of mono‐sort hydroxyl functionalities, calculated using a chemical derivatization technique.

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