Growth rate, morphology, chemical composition and oligomerization state of plasma polymer films made from acrylic and methacrylic acid under dielectric barrier discharge

Plasma polymerization is a powerful coating technology for many technological areas, notably in the coating of biomaterials, particularly when it is applied under atmospheric pressure conditions which allow to avoid expensive pumping systems. In the present investigation, the properties of coatings based on acrylic acid and on methacrylic acid prepared using atmospheric pressure plasma in dielectric barrier discharge conditions and at atmospheric pressure under various operating parameters were compared. The obtained films were characterized using different analytical and spectroscopic techniques with the aim to understand the influence of small changes in the monomer structure as well as in the operational plasma parameters on the film structure. Differences in chemical structure, deposition rate and functional group preservation were determined using FTIR, X-ray photoelectron spectroscopy combined with chemical labeling, and mass spectrometry (MALDI-TOF). As a main result, we show the possibility to quickly design architectures with tunable carboxylic functions by modifying the structure of the used monomer as well as the plasma processing parameters. Our investigation is one of the first in which the molar mass distribution of the plasma polymers, made either from acrylic acid or methacrylic acid, is directly measured from the solid state film without selective solvent extraction.