Christopher Soles, Ryan Nieuwendaal, Huagen H. Peng
The wide-spread interest in the dynamical property of organic materials under strong states of confinement largely began with differential scanning calorimeter (DSC) measurements in the early 90's of the glass transition and heat capacity of glass forming liquids imbibed in a nanoporous support matrix. These seminal studies evidenced reductions in the glass transition temperature (Tg) and the step increase of heat capacity that accompanies Tg for the small molecule liquids encapsulated in controlled pore glasses with pore diameters in the 4 to 73 nm range, with smaller diameters leading to larger deviations. Within a few years, these finite size studies quickly spread to polymeric systems in the form of thin films. Several manuscripts appeared almost simultaneously reporting thickness induced deviations in the glass transition temperature of spin cast polymer films when the film thickness dropped below a critical value. The first of these reports appeared in 1994 using spectroscopic ellipsometery to track the thermal expansion behavior of the polymer films as a function of thickness, identifying thickness induced shifts in the apparent glass transition temperature. Within a few years there were similar reports based on Brillouin light scattering, specular X-ray reflectivity, and positron annihiliation lifetime spectroscopy. Not surprisingly, the results from the different techniques applied to slightly different material systems did not always agree. The debates sparked a wave of literature that has continued to grow over the past two decades.
, Nieuwendaal, R.
and Peng, H.
Polymer Dynamics in Constrained Geometries, Elsevier LTD, Oxford, , [online], https://doi.org/10.1016/B978-0-444-53349-4.00188-6
(Accessed June 5, 2023)