Tarnacka Magdalena, Geppert-Rybczyńska Monika, Dulski Mateusz, Grelska Joanna, Jurkiewicz Karolina, Grzybowska Katarzyna, Kamiński Kamil, Paluch Marian
Institute of Physics, University of Silesia in Katowice, 75 Pułku Piechoty 1, 41-500 Chorzow, Poland.
Institute of Chemistry, University of Silesia in Katowice, Szkolna 9, 40-007 Katowice, Poland.
J Chem Phys. 2021 Feb 14;154(6):064701. doi: 10.1063/5.0040150.
Herein, we examined the effect of finite size and wettability on the structural dynamics and the molecular arrangement of the propylene carbonate derivative, (S)-(-)-4-methoxymethyl-1,3-dioxolan-2-one (assigned as s-methoxy-PC), incorporated into alumina and silica porous templates of pore diameters d = 4 nm-10 nm using Raman and broadband dielectric spectroscopy, differential scanning calorimetry, and x-ray diffraction. It was demonstrated that only subtle changes in the molecular organization and short-range order of confined s-methoxy-PC molecules were detected. Yet, a significant deviation of the structural dynamics and depression of the glass transition temperatures, T, was found for all confined samples with respect to the bulk material. Interestingly, these changes correlate with neither the finite size effects nor the interfacial energy but seem to vary with wettability, generally. Nevertheless, for s-methoxy-PC infiltrated into native (more hydrophilic) and modified (more hydrophobic) silica templates of the same nanochannel size (d = 4 nm), a change in the dynamics and T was negligible despite a significant variation in wettability. These results indicated that although wettability might be a suitable variable to predict alteration of the structural dynamics and depression of the glass transition temperature, other factors, i.e., surface roughness and the density packing, might also have a strong contribution to the observed confinement effects.
在此，我们使用拉曼光谱和宽带介电谱、差示扫描量热法以及X射线衍射，研究了有限尺寸和润湿性对碳酸亚丙酯衍生物（S）-（-）-4-甲氧基甲基-1,3-二氧戊环-2-酮（命名为s-甲氧基-PC）的结构动力学和分子排列的影响，该衍生物被纳入孔径d = 4 nm至10 nm的氧化铝和二氧化硅多孔模板中。结果表明，仅检测到受限的s-甲氧基-PC分子的分子组织和短程有序的细微变化。然而，相对于块状材料，所有受限样品的结构动力学均存在显著偏差，玻璃化转变温度T也有所降低。有趣的是，这些变化既与有限尺寸效应无关，也与界面能无关，而是通常随润湿性而变化。尽管如此，对于渗透到相同纳米通道尺寸（d = 4 nm）的天然（更亲水）和改性（更疏水）二氧化硅模板中的s-甲氧基-PC，尽管润湿性有显著变化，但动力学和T的变化可忽略不计。这些结果表明，尽管润湿性可能是预测结构动力学变化和玻璃化转变温度降低的合适变量，但其他因素，即表面粗糙度和密度堆积，也可能对观察到的受限效应有很大贡献。
