Study On Surface Treatment And Functionalization Of Polymers Based On DBD Plasma

Polymers of low cost,controllable crystallinity,excellent chemical and mechanical stability have promising applications in energy,water treatment,electronics,and biomedical industries.On the other hand,the stability of chemicals also limits their applications.Surface modification is an effective method to improve the application of materials,to endow them with new interfacial properties,and meanwhile,to maintain desirable bulk properties.Conventional surface modification approaches of polymers inevitably have disadvantages like poor versatility,high cost,and cumbersome steps.To address these shortcomings,the present work firstly designed and constructed an atmospheric pressure dielectric barrier discharge（DBD）plasma setup,before being applied for surface functionalization of different polymers.The structures and properties of the plasma-modified polymers were examined by complementary characterization and applications.On this basis,the developed DBD plasma technique was further expanded to the modification of metals,and realized the surface functionalization of metal substrates.The main research contents and conclusions are as below:By using acrylic acid as the precursor and CO₂/N₂ as the working gas,the surface of polytetrafluoroet-hylene（PTFE）membranes was modified by the DBD plasma technique to alter the wettability.Systematic experiments have been carried out to investigate the influence of the gas composition and the plasma exposure time on the composition,morphology,and wettability performance of the PTFE membranes.It is shown that carboxylic functional groups have been successfully grafted on the surface of PTFE by the plasma technique,leading to improved hydrophilicity.The increase of the CO₂ content in CO₂/N₂ mixtures results in an enhanced generation of C-O,C=O,and C-C species,suggesting CO₂ can be converted to hydrophilic functional groups.Moreover,at plasma treatment time of 0～60 s,the hydrophilicity of the PTFE membranes can be improved,while longer plasma treatment time would lead to the degradation of the formed coating,leading to reduced hydrophilicity.The DBD plasma method was further extended to the surface modification of substrates like polyethylene（PE）,polyvinylidene fluoride（PVDF）,and plexiglass,suggesting high versatility of the process.The developed DBD plasma technique is then used for the surface modification of nitrile membranes,where silver acetylacetone（Ag（acac））and copper acetylacetone（Cu（acac）₂）were used as the sources of silver nanoparticles（Ag NPs）and copper oxide（Cu O_x）particles.The results show that Ag NPs and Cu O_x particles prepared by the DBD plasma setup can be strongly absorbed on the surface of the nitrile membranes.Antibacterial tests against Escherichia coli（E.coli）and Staphylococcus epidermidis（S.epidermidis）show the Ag NPs-deposited nitrile membranes possess apparent antibacterial activities,in contrast to the Cu O_x particles-deposited membranes.This simple,rapid,and flexible plasma process together with the antibacterial activities of membranes is expected to provide guidance for the surface modification of polymers with desired properties.The efficient and controllable adsorption of fluorescent patterns is crucial for the basic research and practical application of materials.By adjusting the content of terbium acetylacetonate（Tb（acac）₃）and europium acetylacetonate（Eu（acac）₃）,Tb³⁺/Eu³⁺co-doped Y₂O₃ fluorescent patterns of different fluorescence characteristics were constructed on the surfaces of PVDF,polypropylene（PP）,Polyethersulfone（PES）,and nylon（Nylon）.Y₂O₃-based nanoparticles are rapidly formed in the oxygen free radical and directionally deposited on the substrate surface,resulting in changes of the surface elements,surface morphology and roughness of the substrate to different degrees,and forms clear image areas and non-image areas under ultraviolet（UV）light.To investigate the versatility of the DBD plasma surface modification technique,the thesis further applies this method to metal substrates to form endurable coatings in a green,efficient manner.By using perfluorooctanyltriethoxysilane（POTS）and polyethylene glycol 200（PEG200）as the precursors,metals were modified by the DBD plasma to form stable hydrophilic/hydrophobic coatings.The composition,morphology,surface roughness,and wettability of the metal substrates could be adjusted by the plasma treatment time.Furthermore,the plasma modified substrates also displayed improved corrosion resistance via the salt spray test.The results reveals that the DBD plasma method can serve as an effective method for the surface modification of metals with desirable properties.