Surface evaluation of plasma-modified polysulfone (Udel P-1700) films

The paper presents a new method for the evaluation of surface properties. Polysulfone films modified by plasma treatment in carbon dioxide, nitrogen, and vapors of n-butylamine were taken as test samples. Surface concentrations of acidic or basic functionalities were estimated by contact angle measurements. Aqueous solutions of HCl and NaOH with various pH values were used. The method of surface evaluation is based on fitting the gamma Lcos Theta versus pH (or pOH) relationship with a polynomial and finding its inflection point. The pH (or pOH) values at this point are recalculated into apparent surface concentrations of basic (Or acidic) functionalities by means of Gibbs' and Langmuir's equations. It was found that surfaces contain acidic functionalities (0.15 mu mol/m(2)) when polysulfone was modified in carbon dioxide and basic functionalities (2.50 mu mol/m(2)) for butylamine plasma. Modification with N-2 resulted in the creation of an amphoteric surface.