The Role of Thermal History, Density, and Pressure Changes in the Nonequilibrium Glass Transition Dynamics of Low-Molecular-Weight Poly(phenylmethyl siloxane) (PMPS) under Nanopore Confinement,Macromolecules

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The Role of Thermal History, Density, and Pressure Changes in the Nonequilibrium Glass Transition Dynamics of Low-Molecular-Weight Poly(phenylmethyl siloxane) (PMPS) under Nanopore Confinement
Macromolecules ( IF 5.1 ) Pub Date : 2024-08-17 , DOI: 10.1021/acs.macromol.4c01207
Katarzyna Chat _{1,

2,

3} , Karolina Adrjanowicz _{2,

3} , Ewa Juszyńska-Gałązka ₁

Affiliation

At the nanoscale, various deviations from the typical bulk properties often result from nonequilibrium phenomena. These effects can frequently weaken with time, and their lifetimes depend on many factors. Here, using dielectric spectroscopy, we have studied the equilibration kinetics of low-molecular-weight poly(phenylmethyl siloxane) (PMPS 2.5k) confined in anodized aluminum oxide (AAO) nanopores under up- and down-jump conditions. Through time-dependent measurements, the influence of annealing temperature, depth of the temperature jump, and pore size was systematically analyzed. It has been shown that decreasing annealing temperature and pore size is accompanied by a longer equilibration time. Also, the depth of the temperature jump significantly affects the time required to recover the bulk properties. The greater the distance between preannealing and annealing temperature, the less effectively the system reaches equilibrium state. Furthermore, analysis of volume changes and pressure effects during the equilibration process reveals that after up jumps, the polymer in confined geometry gains volume, while after down jumps, the excess free volume must be eliminated with corresponding changes in pressure. These findings underscore the intricate interplay between thermal history and pressure and density changes governing the equilibration kinetics within confined systems. This research contributes to a deeper understanding of the equilibrium processes of nanopore-confined polymers.

中文翻译：

纳米孔约束下低分子量聚苯基甲基硅氧烷 (PMPS) 的非平衡玻璃化转变动力学中热历史、密度和压力变化的作用

在纳米尺度上，与典型体积特性的各种偏差通常是由非平衡现象造成的。这些影响通常会随着时间的推移而减弱，其寿命取决于许多因素。在这里，我们利用介电光谱研究了阳极氧化氧化铝（AAO）纳米孔中限制的低分子量聚（苯基甲基硅氧烷）（PMPS 2.5k）在上跳和下跳条件下的平衡动力学。通过随时间变化的测量，系统分析了退火温度、温度跳跃深度和孔径的影响。已经表明，降低退火温度和孔径会伴随着更长的平衡时间。此外，温度跃变的深度显着影响恢复整体性能所需的时间。预退火温度和退火温度之间的距离越大，系统达到平衡状态的效率就越低。此外，对平衡过程中体积变化和压力影响的分析表明，在向上跳跃之后，受限几何形状的聚合物获得体积，而在向下跳跃之后，多余的自由体积必须随着压力的相应变化而消除。这些发现强调了热历史与控制受限系统内平衡动力学的压力和密度变化之间复杂的相互作用。这项研究有助于更深入地了解纳米孔限制聚合物的平衡过程。

更新日期：2024-08-17

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