data_availability_Grandi_Soft_Matter.zip

The number of free surfaces in a polymer ultra-thin film has a strong influence on its physical andmechanical properties. In this study, Young’s modulus as well as the glass transition temperatureof multinanolayer coextruded polymer films, hence with no free surfaces, have been measured. Weobserve that contrary to the case of free-standing or supported ultra-thin films, there is no depressionof the glass transition temperature or the Young modulus, but an increase for the latter as the layerthickness decreases, whatever the polymer pair (with various compatibilities). It is proposed thatthis increase is associated with the rise of interphase volume fraction in the films. An interphasemodulus of about 25 GPa can be extracted from the empirical model, about 10 times higher thanthe typical modulus value of a glassy polymer. This value does not appear to depend on the natureof the polymers, meaning that the presence of entanglements at the interfaces is not a key factor toexplain the increase in Young’s modulus of multinanolayer films.