Institute of Physics, University of Silesia, Katowice, Poland.
J Phys Chem B. 2011 Apr 28;115(16):4559-67. doi: 10.1021/jp109135w. Epub 2011 Apr 1.
It was shown recently that ibuprofen revealed a strong tendency to form hydrogen bonded aggregates such as dimers and trimers of either cyclic or linear geometry, which somehow seems to control molecular mobility of that drug [Brás et al. J. Phys. Chem. B2008, 112 (35), 11 087-11 099]. For such hydrogen-bonded liquids, superpositioning of dynamics under various temperature T, pressure P, and volume V conditions, when plotted versus the scaling function of T(-1)V(-γ) (where γ is a material constant), may not always be satisfying. In the present work, we have tested the validity of this scaling for supercooled ibuprofen. In order to do that, pressure-volume-temperature (PVT) measurements combined with isobaric and isothermal dielectric relaxation studies (pressure up to 310 MPa) were carried out. The scaling properties of the examined drug were derived from the fitting of the τ(α)(T,V) dependences to the modified Avramov equation and by analyzing in double logarithmic scale the T(g)(V(g)) dependences, where the glass transition temperature T(g) and volume V(g) were defined for various relaxation times. In view of the obtained results, we conjecture that for ibuprofen the thermodynamic scaling idea works but not perfectly. The slight departure from the scaling behavior is discussed in the context of the hydrogen bonding abilities of the examined system and compared with the results reported for other strongly associated liquids.
最近的研究表明，布洛芬有强烈的倾向形成氢键聚集，如环状或线状的二聚体和三聚体，这似乎控制了药物的分子流动性[Brás 等人，《物理化学杂志 B》2008 年，112（35），11087-11099]。对于这种氢键液体，在各种温度 T、压力 P 和体积 V 条件下的动力学叠加，当绘制为 T(-1)V(-γ)（其中γ是材料常数）的标度函数时，并不总是令人满意。在目前的工作中，我们已经测试了这种超冷布洛芬的标度有效性。为此，我们进行了压力-体积-温度（PVT）测量，并结合等压和等温介电松弛研究（压力高达 310 MPa）。通过将 τ(α)(T,V)依赖性拟合到改进的 Avramov 方程，并通过在双对数尺度上分析 T(g)(V(g))依赖性，其中 T(g)和 V(g)分别定义为各种松弛时间的玻璃化转变温度和体积，从检查药物中得出了标度特性。鉴于所得到的结果，我们推测对于布洛芬，热力学标度思想是有效的，但不是完美的。在氢键能力的背景下讨论了与标度行为的轻微偏离，并与其他强关联液体的结果进行了比较。
