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摘要
In Paper I of this series of two papers we study the main relaxations of a binary glass former made of the low-T-g component tripropyl phosphate (TPP, T-g = 134 K) and of a specially synthesized (deuterated) spirobichroman derivative (SBC, T-g = 356 K) as the non-polymeric high-T-g component for the full concentration range. A large T-g contrast of the neat components is put into effect. Dielectric spectroscopy and different techniques of H-2 nuclear magnetic resonance (NMR) as well as of P-31 NMR spectroscopy allow to selectively probe the dynamics of the components. For all concentrations, two well separated liquid-like processes are identified. The faster alpha(2)-process associated with the low-T-g component TPP shows pronounced dynamic heterogeneities reflected by quasi-logarithmic correlation functions at low TPP concentrations. The slower alpha(1)-process involves the reorientation of the high-Tg component SBC. Its correlation function is Kohlrausch-like as in neat glass formers. The corresponding time constants and consequently their glass transition temperatures T-g1 and T-g2 differ more the lower the TPP concentration is. Plasticizer and anti-plasticizer effect, respectively, is observed. At low temperatures a situation arises that the TPP molecules isotropically reorient in an arrested SBC matrix (T-g2 < T < T-g1). At T < T-g2 the liquid-like reorientation of TPP gets arrested too. We find indications that a fraction of the TPP molecule takes part in the slower alpha(1)-process of the high-T-g component. All the features known from polymer-plasticizer systems are rediscovered in this non-polymeric highly asymmetric binary mixture. In Paper II [ B. Potzschner et al., J. Chem. Phys. 146, 164504 (2017)] we study the secondary (beta-) relaxations of the mixtures. Published by AIP Publishing.
- 出版日期2017-4-28
