Bock D, Kahlau R, Pötzschner B, Körber T, Wagner E, Rössler E A
Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany.
J Chem Phys. 2014 Mar 7;140(9):094505. doi: 10.1063/1.4865945.
Various (2)H and (31)P nuclear magnetic resonance (NMR) spectroscopy techniques are applied to probe the component dynamics of the binary glass former tripropyl phosphate (TPP)/polystyrene-d3 (PS) over the full concentration range. The results are quantitatively compared to those of a dielectric spectroscopy (DS) study on the same system previously published [R. Kahlau, D. Bock, B. Schmidtke, and E. A. Rössler, J. Chem. Phys. 140, 044509 (2014)]. While the PS dynamics does not significantly change in the mixtures compared to that of neat PS, two fractions of TPP molecules are identified, one joining the glass transition of PS in the mixture (α1-process), the second reorienting isotropically (α2-process) even in the rigid matrix of PS, although at low concentration resembling a secondary process regarding its manifestation in the DS spectra. Pronounced dynamical heterogeneities are found for the TPP α2-process, showing up in extremely stretched, quasi-logarithmic stimulated echo decays. While the time window of NMR is insufficient for recording the full correlation functions, DS results, covering a larger dynamical range, provide a satisfactory interpolation of the NMR data. Two-dimensional (31)P NMR spectra prove exchange within the broadly distributed α2-process. As demonstrated by (2)H NMR, the PS matrix reflects the faster α2-process of TPP by performing a spatially highly hindered motion on the same timescale.
运用多种（2）H和（31）P核磁共振（NMR）光谱技术，在整个浓度范围内探究二元玻璃形成剂磷酸三丙酯（TPP）/聚苯乙烯-d3（PS）的组分动力学。将结果与先前发表的关于同一体系的介电谱（DS）研究结果[R. 卡劳、D. 博克、B. 施密特克和E. A. 罗斯勒，《化学物理杂志》140, 044509 (2014)]进行定量比较。虽然与纯PS相比，混合物中PS的动力学没有显著变化，但鉴定出了两部分TPP分子，一部分在混合物中参与PS的玻璃化转变（α1过程），另一部分即使在PS的刚性基质中也进行各向同性重排（α2过程），尽管在低浓度下，就其在DS光谱中的表现而言类似于二级过程。发现TPP的α2过程存在明显的动力学不均匀性，表现为极其伸展的准对数受激回波衰减。虽然NMR的时间窗口不足以记录完整的关联函数，但覆盖更大动力学范围的DS结果为NMR数据提供了令人满意的插值。二维（31）P NMR光谱证明在广泛分布的α2过程中存在交换。如（2）H NMR所示，PS基质通过在相同时间尺度上进行空间高度受阻的运动反映了TPP较快的α2过程。
