Mobility Gradient of Poly(ethylene terephthalate) Chains near a Substrate Scaled by the Thickness of the Adsorbed Layer

Abstract

The question of how to scale the mobility gradient of polymer chains near a substrate in supported ultrathin polymer films is a great challenge. In this paper, a mobility gradient of poly­(ethylene terephthalate) (PET) chains near a substrate is characterized by cold crystallization. We found that either decreasing the PET film thickness or increasing the absorbed layer thickness consistently reveals three characteristic film thicknesses, which are all linearly dependent on the adsorbed-layer thickness. At the first thickness, the low-temperature peak of the top surface crystallization starts to shift toward the high-temperature peak of the bulk-like polymer crystallization; at the second thickness, it arrives there; and at the third thickness, crystallization is completely suppressed. The three kinds of film thicknesses characterize the depth profile of the local dynamics, reflecting the long-range effects of the substrate, which could be scaled by the thickness of the adsorbed layer.

Temperature-Dependent Spectroscopic Ellipsometry of Thin Polymer Films

“…Another example can be taken from the work of Xu et al 118 who focused on the study of the mobility gradient of PET chains near the substrate. The authors presented the dependence Δ( T ) and for thin PET films; see Figure 11 a, where the temperatures of these thermal transitions were marked.…”

“…We will only mention here that the interpretation regarding the effect of layer thickness on the characteristic temperatures of thermal transitions is confirmed by AFM. 118 It is also worth noting that, as in the case of DSC, subsequent heating and cooling cycles can be used in temperature-dependent ellipsometry to monitor structural changes in the polymer layer under investigation.…”

“… Temperature dependence of the ellipsometric angle Δ and its derivative for the thin PET film (a) and temperature of cold crystallization on the surface and for a bulklike part of films of PET with various thicknesses (b). Adapted with permission from ref ( 118 ). Copyright 2017 American Chemical Society.…”

Cyclic Topology Enhancing Structural Ordering and Stability of Comb-Shaped Polypeptoid Thin Films against Melt-Induced Dewetting

“… 20 − 31 Depending on the polymer characteristics and thermal processing history, polymer chains that directly interact with the substrate surface via physisorption can possess different chain conformation, adsorbed amount, surface coverage, and density on the substrate. 20 , 21 , 24 , 26 − 28 , 30 , 32 Recent studies have revealed a strong correlation between autophobic dewetting of thin polymer films and the nanoarchitectures/conformations of adsorbed chains at the interface, where the conformational difference between the adsorbed chains and free chains plays a significant role. 25 , 29 − 31 Interestingly, by using the top-down solvent leaching method (also known as Guiselin’s approach), 33 it has been found that cyclic PS melt forms thicker irreversibly adsorbed layers on solid substrates than the linear PS melt, which can dramatically alter the interfacial effect on chain dynamics and dewetting behaviors of polymer thin films.…”

Thermal Transitions in P3HT:PC60BM Films Based on Electrical Resistance Measurements

“…A spectroscopic ellipsometer equipped with a temperature adapter enables the thermal analysis of the tested sample by optical measurements during controlled heating or cooling. Literature studies indicate that the characteristic temperatures of thermal transitions can be determined by analysing raw ellipsometric data on the basis of ellipsometric angles or their temperature derivatives [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ]. The temperature dependence of physical quantities, such as film thickness, its coefficient of thermal expansion, refractive index, and ellipsometric data modelling [ 54 , 55 , 56 , 57 , 58 , 59 , 60 ] is also explored.…”