The Role of Density Fluctuations and Interfacial Energy in Controlling the Dynamics of the Polymers Confined within the Anodic Aluminum Oxide

In this paper, we performed dielectric and calorimetric studies on the dynamics of the three polymer brushes based on poly(mercaptopropylmethylsiloxane, PMMS), grafted with various acrylates monomers that were infiltrated into anodic aluminum oxide (AAO) porous templates characterized by the constant pore size, $$. Additionally, systematic high pressure dielectric investigations were done along with the contact angle measurements to understand behaviour of these polymer in the nanospatial restriction. A special focus was paid to address the shift of the $$ and $$ corresponding respectively to the “interfacial” and the “core” fractions, of polymers with respect to the bulk samples. Results showed that changes of both $$ s (calculated as $$) were comparable across copolymers. Nevertheless, to make more general conclusions, we compared our data with the ones collected for the other polymers of similar molecular weight measured at high pressures and within AAO membranes. It was found that the interfacial energy ($$) might not be enough to predict the variation of both $$ and/or $$. However, some relationship between the pressure coefficient of the glass transition temperature $$ and $$ as well as $$ was noted. This suggests that polymers that are more sensitive to density variations show a larger depression of $$ under confinement. Though these relationships are not always satisfied. It means that the depression of $$ of given polymer under confinement is not governed by a single parameter, but is controlled by the interplay between the interfacial energy, pressure sensitivity of the segmental dynamics and molecular weight of the polymer.