Dynamics of macromolecules: A challenge for surface analysis

Abstract

Abstract XPS and contact angle measurement have been used to study oxygen–plasma‐treated polypropylene (PP) surfaces aged at variable temperatures. Surface rearrangement leading to low wettabillity has been observed, without alteration of the surface composition, as determined by XPS. Experimental results have been interpreted in terms of internal rearrangements of a modified layer, <5 nm thick, formed on top of the PP and immiscible with it. We also modelled the composition of the surface layer and calculated the relative mobility of modified and non‐modified polymer chains. On this basis, the experimentally observed behaviour can be interpreted in terms of surface rearrangement driven by a compromise between striving for lower surface tension and maximizing inter‐and intramolecular interactions, mainly hydrogen bonds. The surface composition observed after treatment with plasma, corona, flame or other for enhancing surface tension is then time dependent. For this reason, the procedure used for surface analysis, namely the time allowed for surface equilibration, should be specified in reports.