The present invention relates to methods of modifying the chemical structure of a surface by covalently attaching molecules containing desired functional groups on the surface using plasma energy. In these methods, chemical compounds containing the desired functional groups and having a vapor pressure lower than 0.001 bar are exposed in the plasma chamber together with the substrate. Surface area of the chemical compound is optimized to generate adequate evaporation rate. The modification of the substrate surface is achieved in a plasma state generated from the vapor of the chemical compounds; while the evaporation of the chemical compounds is accelerated by the plasma energy. Methods for producing non-fouling surface by covalently attaching ethylene glycol oligomers on the surface are disclosed.