Dominance of density variations in determining the molecular weight dependence of surface tensions of polymer melts

Abstract

We utilize exact thermodynamic relationships to separate the role of density variations and chain end segregation to surfaces in determining the molecular weight dependence of the surface tensions of polymer melts. By utilizing standard mean-field treatments we find that density effects dominate, except in special cases, where the chain ends are strongly attracted or repelled from the surfaces. These results stress that PVT measurements are generally sufficient to properly capture the molecular weight dependence of γ for normally encountered polymer melts.