Glassy Dynamics and Glass Transition in Nanometric Thin Layers of Polystyrene

Abstract

Broadband dielectric spectroscopy (BDS), spectroscopic vis-ellipsometry (SE), X-ray reflectometry (XRR), and alternating current (ACC) as well as differential scanning calorimetry (DSC) are combined to study glassy dynamics and the glass transition in nanometric thin (≥5 nm) layers of polystyrene (PS) having widely varying molecular weights (27 500−8 090 000 g/mol). For the dielectric measurements two sample geometries are employed, the common technique using evaporated electrodes and a recently developed approach taking advantage of nanostructures as spacers. All applied methods deliver the concurring result that deviations from glassy dynamics and from the glass transition of the bulk do not exceed margins of ±3 K independent of the layer thickness and the molecular weight of the polymer under study. Our findings are discussed in the context of the highly controversial literature and prove that an appropriate sample preparation is of paramount importance.

In situ investigation of vapor-deposited glasses of toluene and ethylbenzene via alternating current chip-nanocalorimetry

“…Besides the step height the experiments at small film thicknesses revealed the dynamic glass transition temperature to be independent of film thickness in accordance to other works [89,132,133] (Figure 52). On the contrary, many publications proved a glass transition temperature dependence on film thickness [61,134].…”

Calorimetric evidence for a mobile surface layer in ultrathin polymeric films: poly(2-vinyl pyridine)

“…As mentioned above, this is in agreement with AC-chip calorimetry studies on other polymers. 19,[39][40][41][42]58 The temperature dependence of the relaxation rates can be described by the Vogel/Fulcher/Tammann (VFT) equation [59][60][61] …”

Confinement enhances dispersion in nanoparticle–polymer blend films

“…On the other hand, very little is known or understood about the nature of dispersion of nanoparticles in thin polymer films [5][6][7]9,10,12 . This is a bit surprising since, a vast amount of research has been devoted to understanding of structure and properties of thin polymer films, especially those related to the perturbation of chain conformation [17][18][19][20][21] and glass transition due to confinement [5][6][7][8]11,[22][23][24][25] . Although there is significant progress in understanding the chain conformation with confinement, some conflicting reports still exist [18][19][20]26,27 .…”

“…Although there is significant progress in understanding the chain conformation with confinement, some conflicting reports still exist [18][19][20]26,27 . Similarly, in the case of glass transition of thin polymer films, contradictory reports on finite size effects on T g in polymer thin films have emerged [5][6][7][8][22][23][24] . If polymer chain conformations do get perturbed due to confinement, does it affect the state of dispersion and other physical properties in thin films of PNCs?…”