Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany.
J Chem Phys. 2013 Aug 14;139(6):064508. doi: 10.1063/1.4816374.
By means of dielectric as well as (2)H and (31)P nuclear magnetic resonance spectroscopy (NMR) the component dynamics of the binary glass tripropyl phosphate (TPP)/polystyrene (PS/PS-d3) is selectively investigated for concentrations distributed over the full range. We study the secondary (β-) relaxation below T(g), which is found in all investigated samples containing TPP, but not in neat polystyrene. The dielectric spectrum of the β-process is described by an asymmetric distribution of activation energies, essentially not changing in the entire concentration regime; its most probable value is E/k ≅ 24 T(g). Persistence of the β-process is confirmed by (31)P NMR Hahn-echo and spin-lattice relaxation experiments on TPP, which identify the nature of the β-process as being highly spatially hindered as found for other (neat) glasses studied previously, or re-investigated within this work. The corresponding (2)H NMR experiments on PS-d3 confirm the absence of a β-process in neat PS-d3, but reveal a clear signature of a β-process in the mixture, i.e., polystyrene monomers perform essentially the same type of secondary relaxation as the TPP molecules. Yet, there are indications that some fractions of PS-d3 as well as TPP molecules become immobilized in the mixture in contrast to the case of neat glasses. We conclude that in a binary glass the β-process introduced by one component induces a highly similar motion in the second component, and this may be taken as an indication of its cooperative nature.
通过介电以及 (2)H 和 (31)P 核磁共振光谱 (NMR)，我们选择性地研究了二元玻璃三丙磷酸酯 (TPP)/聚苯乙烯 (PS/PS-d3) 在整个浓度范围内的组分动力学。我们研究了低于 Tg 的次级（β-）弛豫，它存在于所有含有 TPP 的研究样品中，但在纯聚苯乙烯中不存在。β-过程的介电谱由激活能的不对称分布描述，基本上在整个浓度范围内没有变化；其最可能的值为 E/k ≅ 24 Tg。通过 TPP 的 (31)P NMR Hahn 回波和自旋晶格弛豫实验证实了 β-过程的持久性，这些实验确定了 β-过程的本质是高度空间受限的，与之前研究的其他（纯）玻璃相同，或者在本工作中重新研究。对 PS-d3 的相应 (2)H NMR 实验证实了纯 PS-d3 中不存在 β-过程，但在混合物中显示出 β-过程的明显特征，即聚苯乙烯单体基本上执行与 TPP 分子相同类型的次级松弛。然而，有迹象表明，与纯玻璃的情况相比，混合物中的一些 PS-d3 以及 TPP 分子会被固定。我们得出结论，在二元玻璃中，一种成分引入的 β-过程会在第二种成分中引起高度相似的运动，这可以作为其协同性质的一个迹象。
