Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland.
J Phys Chem B. 2010 May 20;114(19):6579-93. doi: 10.1021/jp910009b.
Dielectric spectroscopy (DS) was used to investigate the relaxation dynamics of supercooled and glassy ibuprofen at various isobaric and isothermal conditions (pressure up to 1750 MPa). The ambient pressure data are in good agreement with that reported previously in the literature. Our high pressure measurements revealed validity of temperature-pressure superpositioning (TPS) for the alpha-peak. We also found that the value of the fragility index decreases with compression from m = 87 +/- 2 at atmospheric pressure to m = 72.5 +/- 3.5 at high pressure (p = 920 MPa). The drop of fragility observed in our experiment was discussed in the framework of the two-order-parameter (TOP) model. In addition, we have also studied crystallization kinetics in a liquid state of examined drug at ambient and high pressure. We found out that, for the same structural relaxation time/same viscosities, the samples prepared by compression of liquid at high temperatures have significantly elongated induction times as well as overall crystallization times (sample 2: t(0) approximately = 4 h, t(1/2) approximately = 37.5 h; sample 3: t(0) approximately = 5.6 h, t(1/2) approximately = 49 h) compared to that held at lower temperature and ambient pressure (sample 1: t(0) approximately = 1.2 h, t(1/2) approximately = 12.2 h). A possible explanation of this finding is also given.
介电谱（DS）被用于研究在各种等压和等温条件（压力高达 1750 MPa）下过冷和玻璃态布洛芬的弛豫动力学。环境压力数据与文献中先前报道的结果非常吻合。我们的高压测量结果表明，α-峰的温度-压力叠加（TPS）是有效的。我们还发现，随着压力从大气压下的 m = 87 ± 2 压缩到高压下的 m = 72.5 ± 3.5，脆性指数的值降低。我们在实验中观察到的脆性下降在双参数模型的框架内进行了讨论。此外，我们还研究了在环境压力和高压下研究药物的液态结晶动力学。我们发现，对于相同的结构弛豫时间/相同的粘度，在高温下通过压缩液体制备的样品具有明显延长的诱导时间和整体结晶时间（样品 2：t(0)大约 = 4 h，t(1/2)大约 = 37.5 h；样品 3：t(0)大约 = 5.6 h，t(1/2)大约 = 49 h），与在较低温度和环境压力下保持的样品（样品 1：t(0)大约 = 1.2 h，t(1/2)大约 = 12.2 h）相比。对此发现也给出了可能的解释。
