Physical Aging of Polystyrene Confined in Anodic Aluminum Oxide Nanopores

Abstract

We investigated the glassy dynamics of polystyrene (PS) confined in anodic aluminum oxide (AAO) nanopores by differential scanning calorimetry. Based on the outcome of our experiments, we show that the cooling rate applied to process the 2D confined PS melt has a significant impact on both the glass transition and the structural relaxation in the glassy state. A single glass transition temperature (T g) is observed in quenched samples, while slow-cooled PS chains show two T gs corresponding to a core–shell structure. The former phenomenon resembles what is observed in freestanding structures, while the latter is imputed to the adsorption of PS onto AAO walls. A more complex picture was drawn for physical aging. In the case of quenched samples, we observed a non-monotonic trend of the apparent aging rate that in 400 nm pores, reaches a value almost twice as larger than what is measured in bulk and decreases upon further confinement in smaller nanopores. For slow-cooled samples, by adequately varying the aging conditions, we were able to control the equilibration kinetics and either separate the two aging processes or induce an intermediate aging regime. We propose a possible explanation of these findings in terms of distribution in free volume and the presence of different aging mechanisms.

Chemical Etching, Thermally Driven Combination Strategy to Fabricate Superhydrophobic Fe-Based Amorphous Coatings with Excellent Anticorrosion Property: Based on Hydroxylation Effect

“…From Figure 3d, the To investigate the oxidation state of the Etched AMC, the changes in the chemical bonding states of the main elements, especially Fe, Cr, and O, before and after etching were analyzed by XPS. 6 Figure 3a shows the resolved peaks of Fe 2p 3/2 in the assprayed AMC; 9 the spectra can be divided into four peaks corresponding to metal Fe m , Fe ox 2+ , Fe ox 3+ , and Fe hy 3+ . The relative contents of Fe ox 3+ and Fe hy 3+ increased significantly and the relative content of Fe m decreased after etching (Figure 3d), indicating a significant oxidation reaction of Fe elements (Fe ox 3+ : 33.3% to 42.1%, Fe hy 3+ : 17.1% to 31.1%, Fe m : 43.3−26.8%).…”

Improved Electrochemical Performance of LiMn0.6Fe0.4PO4 via Chitosan‐Derived Nitrogen‐Doped Carbon Coating

“…[9] Despite this promising potential, LiMnPO 4 faces challenges such as low electronic conductivity, ion diffusion coefficient, and the impediment of the Jahn Teller effect on commercialization. [10][11] Addressing these challenges, the exploration of a LiMn x Fe 1-…”

Tunability and molecular weight dependence of the physical aging behavior of polystyrene and poly(methyl methacrylate) films

“…While many studies have focused on tuning the physical aging behavior of polymers with intrinsic microporosity for gas separation applications, [54][55][56][57][58] similar research efforts for commodity polymers such as PS and PMMA are limited. Existing studies primarily involve imposing a specific confinement geometry, [59][60][61] modifying chain topology 6 or introducing nanofillers into the bulk material. 62 Therefore, it is important to obtain a better understanding of the relationship between fractional free volume and physical aging behavior for commodity polymers like PS and PMMA.…”