Guidelines for Preparation of Plasma-polymer in View of Surface Functionalization of Solid Materials.

Abstract

Guidelines for surface functionalization of solid materials using plasma technique were made up in view of preparation of hydrophilic polymer films from oxygen- containing organic monomers. Profiles of deposition rates of the polymers on substrates along the monomer flow were obtained from the film thicknesses formed for a unit of time. The data brought about useful information to explore activity of the various monomers towards plasma polymerization. It also suggested the existence of optimum operative conditions to obtain the desired functions of the polymer films. Unsaturated bonds, especially triple bonds of the monomers led to high deposition rates with low wattage of radiofrequency power. Such local spot in the chemical structure was defined as polymerization site. Oxygen atoms in the polar groups of the monomers, especially hydroxyl groups, remained in the resultant polymers under such soft plasma conditions. The oxygen atoms induced hydrophilicity not only from the atom contents but also from the spatial arrangement in molecular structures of the polymers. Thus, groups of the monomers such as -OH or -COON were defined as functional site. Propargyl alcohol (2-propyn-1-ol) was found to be the most promising monomer at present. Addition of water in the same monomer influenced the resultant polymer considerably. Increased water content of the monomer reduced the deposition rate, while it raised the oxygen content, and resulted in enhanced hydrophilicity. It appeared that the unsaturated bonds of the polymer captured oxygen atoms from the plasma-dissociated water vapor.