Interfacial Effect in Supported Thin PET Films Covered with a Thin PPO Layer

Abstract

The thickness dependent chain mobility in polymer films influenced by the interfacial effect was investigated by the cold crystallization behavior of thin poly­(ethylene terephthalate) (PET) films covered by a thin poly­(2,6-dimethyl-1,4-phenyleneoxide) (PPO) layer to eliminate the free surface effect. Two characteristic film thicknesses were observed, which were related to the long-range perturbations of the interfacial effect. Below the first thickness (h s*), the bulk-like crystallization temperature of PET films begins to shift upward, and below the second thickness (h n*), crystallization of PET films is completely suppressed. These two characteristic thicknesses are proportional to the adsorbed layer thickness. We found that h s* is much greater than the thickness of the PET film with a free surface, while h n* is independent of the free surface. This result indicated that the thickness for the suppression of polymer film dynamics can be increased by removing the contribution of the free surface. The value of h n * independent of the free surface may be attributed to the fact that the chain conformation within this thickness adopts the chain conformation at the interface, causing the “free surface” to vanish. The chain conformations affected by the substrate are another cause of long-range perturbations.

The role of the molecular weight of the adsorbed layer on a substrate in the suppressed dynamics of supported thin polystyrene films

“…Similar results were also reported in a study which found that the distance of the suppressed local dynamics of poly(ethylene terephthalate) from the substrate could be scaled by the adsorbed layer thickness. 20,22 This effect of adsorbed chains on the dynamics of thin films is usually attributed to the formation of an overlap zone between the adsorbed layer and the upper free polymer chains, in which the neighboring polymer chains efficiently entangle with the loops of the adsorbed chains and suppress the chain mobility near the solid substrate. The thickness of the overlap region between the bulk-like layer and the adsorbed chains increases with an increase in h ads / R g , further increasing the propagation distance of the interfacial effect.…”

Spatially Heterogeneous Dynamics in Supported Ultrathin Poly(ethylene terephthalate) Films Depend on the Thicknesses of the Film and the Adsorbed Layer

“…The effect of h ads on the surface mobility of the PET films was further investigated through controlling the value of h ads by annealing the PET films at 554 K for different times and confirmed by the solvent-leaching process as previously reported. 24,44 The relationships between 1/t 1/2 and h with h ads = 3.5 and 0.5 nm are also displayed in Figure 2b. It is obvious that the same plateau also can be observed in the high h region and similarly three turning points also exist.…”

Conductive Polymers for Flexible and Stretchable Organic Optoelectronic Applications

“…In recent years, the rapid development of organic optoelectronic devices and soft and wearable materials has further stimulated researcher’s enthusiasm on the mobility of polymer films . Studies have found that the mobility of polymer thin films has a very important impact on the performance of organic photoelectric materials. − It was known that nanoconfinement of polymers to nanometer-scale dimensions leads to special kinetic and thermodynamic properties due to the interface effect and finite-size effect, further influencing the performance of polymer thin films. , Nanoconfinement can change many physical properties of polymers, like lowering the glass transition temperature and modulus and increasing the mechanical ductility, which are desirable for stretchable materials. Thus, the confinement effect is important for improving the mechanical properties of flexible and stretchable devices.…”

“…60−62 It was known that nanoconfinement of polymers to nanometer-scale dimensions leads to special kinetic and thermodynamic properties due to the interface effect and finite-size effect, further influencing the performance of polymer thin films. 59,63 Nanoconfinement can change many physical properties of polymers, like lowering the glass transition temperature 64 and modulus 65 and increasing the mechanical ductility, 66 which are desirable for stretchable materials. Thus, the confinement effect is important for improving the mechanical properties of flexible and stretchable devices.…”