Glass transition dynamics of stacked thin polymer films

Abstract

The glass transition dynamics of stacked thin films of polystyrene and poly(2-chlorostyrene) were investigated using differential scanning calorimetry and dielectric relaxation spectroscopy. The glass transition temperature T(g) of as-stacked thin polystyrene films has a strong depression from that of the bulk samples. However, after annealing at high temperatures above T(g), the stacked thin films exhibit glass transition at a temperature almost equal to the T(g) of the bulk system. The α-process dynamics of stacked thin films of poly(2-chlorostyrene) show a time evolution from single-thin-film-like dynamics to bulk-like dynamics during the isothermal annealing process. The relaxation rate of the α process becomes smaller with increase in the annealing time. The time scale for the evolution of the α dynamics during the annealing process is very long compared with that for the reptation dynamics. At the same time, the temperature dependence of the relaxation time for the α process changes from Arrhenius-like to Vogel-Fulcher-Tammann dependence with increase of the annealing time. The fragility index increases and the distribution of the α-relaxation times becomes smaller with increase in the annealing time for isothermal annealing. The observed change in the α process is discussed with respect to the interfacial interaction between the thin layers of stacked thin polymer films.

Glass Transition Phenomenon for Conjugated Polymers

“…It also has the capability to measure the polymer ultrathin film in the nanometer scale. However, the sample preparation is time consuming since it requires the stacking of several hundred layers of ultrathin film in order to meet the mass requirement . With the new developments of the nanocalorimetry, including flash DSC and AC‐chip calorimetry (We note here that the modulated DSC and the AC‐chip calorimetry are considered as dynamic measurements of T g ), which has the mass requirement of nanogram, measuring the T g of sub‐100 nm a single layer of polymer ultrathin film with DSC becomes possible and has drawn increasing attention …”

Poly(methyl methacrylate) nanotubes in AAO templates: Designing nanotube thickness and characterizing the T-confinement effect by DSC

“…Although a typical conventional DSC sample requires only a few milligrams of material for analysis, it is challenging to create ultrathin film samples for DSC because they possess exceedingly little mass, have a tendency to repel each other due to the accumulation of static charge, and require a large amount of time and effort to prepare. [2][3][4][5][6] For example, Fukao and coworkers studied the T g -confinement behavior of free-standing PS films using DSC. 2 For the thinnest sample, over 400 thin films were created by spin coating, removing the films from substrates by floating them on water, and then stacking the films into a DSC sample pan.…”

“…[2][3][4][5][6] For example, Fukao and coworkers studied the T g -confinement behavior of free-standing PS films using DSC. 2 For the thinnest sample, over 400 thin films were created by spin coating, removing the films from substrates by floating them on water, and then stacking the films into a DSC sample pan. Wang and Zhou studied the T g of thin films of fully cured epoxy polymer as a function of thickness.…”

21st Century Advances in Fluorescence Techniques to Characterize Glass‐Forming Polymers at the Nanoscale

“…Even with signal‐strength limitations, we note that several studies have used conventional DSC to measure T g of stacked ultrathin films . These experiments involved stacking dozens, and in some cases hundreds, of films, and their tedious sample preparation prevent their wide adoption.…”