Nanorheology with a Conventional Rheometer: Probing the Interfacial Properties in Compatibilized Multinanolayer Polymer Films

Measuring the viscoelastic behavior of polymers in the vicinity of a surface or under confinement is an experimental challenge. Simple rheological tests of nanolayered films of polyethylene/polyamide 6 compatibilized in situ during the coextrusion process enabled the probing of these interfacial properties. Taking advantage of the different melting points and of the multiplication of the number of interfaces, a drastic increase of dynamic moduli was reported when increasing the interphase volume fraction in the films. A solid-like behavior for the interphase was identified. The complex viscosity of nanolayered films as a function of angular frequency was quantitatively captured for all samples using a weighted mixing law of bulk and interphase viscosities, without additional adjusting parameters, highlighting the interfacial synergy developed in nanolayered polymer films.