Surface Functionalization of Macroporous Polymeric Materials by Treatment with Air Low Temperature Plasma

Abstract

Polystyrene/divinylbenzene (PS-DVB) macroporous monoliths obtained using highly concentrated emulsions as templates show a superhydrophobic behaviour, restricting their potential technological applications, especially those related to adhesion and wetting. Air plasma treatments were carried out in order to modulate wetting properties, modifying the surface chemical composition of macroporous polystyrene/divinylbenzene materials. The superhydrophobic behaviour was rapidly suppressed by air plasma treatment, greatly reducing the water contact angle, from approximately 150 degrees to approximately 90 degrees, in only 10 seconds of treatment. The new surface chemical groups, promoted by plasma active species, were characterized by surface analysis techniques with different depth penetration specificity (contact angle, XPS, FTIR and SEM). Results demonstrated that very short treatment times produced different chemical functionalities, mainly C-O, C=O, O-C=O and C-N, which provide the materials with predominantly acidic surface properties. However, plasma active species did not penetrate deeply through the interconnected pores of the material. FTIR analysis evidenced that the new hydrophilic surface groups promoted by plasma active species are in a negligibly concentration compared to bulk chemical groups, and are located in a very thin surface region on the PS-DVB monolith surface (significantly below 2 microm). XPS analysis of treated monoliths revealed a progressive increase of oxygen and nitrogen content as a function of plasma treatment time. However, oxidation of the PS-DVB monoliths surface prevails over the incorporation of nitrogen atoms. Finally, SEM studies indicated that the morphology of the plasma treated PS-DVB does not significantly change even for the longest air plasma treatment time studied (120 s).

Influence of irrigation conditions in the germination of plasma treated Nasturtium seeds

“…An advanced ATR correction algorithm (OMNIC 7.3 from Thermo Electron Corporation) was used to correct for band intensity distortion, peak shifts and polarisation effects. Corrected ATR spectra were found quite comparable to their transmission equivalents 48 . Spectra were normalized to the peak corresponding to C-O deformation of carbohydrates and lignin (1010 cm −1 ).…”

“…After prolonged plasma exposure, the shape of the convolution band developed a little shoulder in the region (400–402 eV) attributed to nitrogen oxides. The origin of these surface C-NO x groups must be linked to the oxidation of C-N surface groups, although the adsorption of NO x species formed in the plasma phase cannot be discarded 48 . Overall, the formation of these surface groups can be interpreted as resulting from a progressive plasma oxidation removal of the lipids and carbohydrates forming the surface coat.…”

Physicochemical surface analysis and germination at different irrigation conditions of DBD plasma‐treated wheat seeds

“…Corrected ATR spectra were found to properly reproduce the band position and shape of their transmission equivalents. [ 31 ] The background signal was extracted by means of linear backgrounds applied to the ranges 4,000–3,665 cm −1 , 3,665–3,000 cm −1 , 3,000–2,650 cm −1 , 2,650–2,412 cm −1 , 2,412–2,271 cm −1 , 2,271–1,800 cm −1 , 1,800–1,486 cm −1 , 1,486–1,186 cm −1 , and 1,186–830 cm −1 . Spectra were normalized on the basis of the C–O–C stretching vibration peak located at 1,031 cm −1 .…”

Hydrophobic Coatings on Cotton Obtained by in Situ Plasma Polymerization of a Fluorinated Monomer in Ethanol Solutions

“…An advanced ATR correction algorithm (OMNIC 7.3 from Thermo Electron Corporation) was used in order to correct for band intensity distortion, peaks shifts, and polarization effects. Corrected ATR spectra were found highly comparable to their transmission equivalents …”