The aim of this work is the production and characterization of plasma polymerized acetaldehyde thin films. These films show highly polar species, are hydrophilic, organophilic and easily adsorb organic reactants with CO radicals but only allow permeation of reactants with OH radicals. The good step coverage of films deposited on aluminum trenches is useful for sensor development. Films deposited on hydrophobic substrates may result in a discontinued layer, which allows the use of preconcentration in sample pretreatment. Deposition on microchannels showed the possibility of chromatographic columns and/or retention system production to selectively detect or remove organic compounds from gas flows.

The hydrolization of thin films obtained by tetraethoxysilane plasma polymerization results in the formation of a nanochanneled silicone like structure that could be useful for the production of selective membranes. Therefore, the aim of this work is to test the permeation properties of hydrolyzed thin films. The films were tested for: 1) permeation of polar organic compounds and/or water in gaseous phase and 2) permeation of salt in liquid phase. The efficiency of permeation was tested using a quartz crystal microbalance (QCM) technique in gas phase and conductimetric analysis (CA) in liquid phase. The substrates used were: silicon for characterization of the deposited films, piezoelectric quartz crystals for tests of selective membranes and cellophane paper for tests of permeation. QCM analysis showed that the nanochannels allow the adsorption and/or permeation of polar organic compounds, such as acetone and 2-propanol, and water. CA showed that the films allow salt permeation after an inhibition time needed for hydrolysis of the organic radicals within the film. Due to their characteristics, the films can be used for grains protection against microorganism proliferation during storage without preventing germination.

The possibility of preconcentration on microchannels for organic compounds in gas or liquid phases was evaluated. Microstructures with different geometries were mechanically machined using poly(methyl methacrylate) - PMMA as substrates and some cavities were covered with cellulose. The surfaces of the microchannels were modified by plasma deposition of hydrophilic or hydrophobic films using 2-propanol and hexamethyldisilazane (HMDS), respectively. Double layers of HMDS + 2-propanol were also used. Adsorption characterization was made by Quartz Crystal Measurements (QCM) technique using reactants in a large polarity range that showed the adsorption ability of the structures depends more on the films used than on the capillary phenomena. Cellulose modified by double layer film showed a high retention capacity for all gaseous compounds tested. However, structures without plasma deposition showed low retention capacity. Microchannels modified with double layers or 2-propanol plasma films showed higher retention than non-modified ones on gas or liquid phase.

Hexametildisilazane (HMDS) plasma polymerized thin films obtained using low frequency power supplies can be used to make adsorbent films and turn surfaces hydrophobic. The aim of this work was to verify the hydrophobicity and adsorption properties of HMDS thin films (with and without the addition of oxygen, resulting in double or single layer films) obtained using an inductive reactor powered with a 13.56 MHz power supply. Single and double layer thin films were deposited on silicon for film characterization, polypropylene (PP) for ultraviolet (UVA/UVC) resistance tests, piezoelectric quartz crystal for adsorption tests. The double layer (intermixing) of HMDS plasma polymerized films and HMDS plasma oxidized surfaces showed a non-continuous layer. The films showed good adhesion to all substrates. Infrared analysis showed the presence of CHn, SiCH3, SiNSi and SiCH2Si within the films. Contact angle measurements with water showed hydrophobic surfaces. UVA/UVC exposure of the films resulted in the presence of cross-linking on carbonic radicals and SiCH2Si formation, which resulted in a possible protection of PP against UVA/UVC for a duration of up to two weeks. Adsorption tests showed that all organic reactants were adsorbed but not water. Plasma etching (PE) using O2 showed that even after 15 minutes of exposure the films do not change their hydrophobic characteristic but were oxidized. The results point out that HMDS films can be used: for ultraviolet protection of flexible organic substrates, such as PP, for sensor and/or preconcentrator development, due to their adsorption properties, and in spatial applications due to resistance for O2 attack in hostile conditions, such as plasma etching.