Arrese-Igor S, Arbe A, Alegría A, Colmenero J, Frick B
Departamento de Física de Materiales, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Apartado 1072, 20080 San Sebastián, Spain.
J Chem Phys. 2005 Jul 1;123(1):014907. doi: 10.1063/1.1948372.
We have investigated the dynamics of phenylene rings in glassy bisphenol-A (BPA) polycarbonate (PC) by means of quasielastic neutron scattering. Taking advantage of selective deuteration of the samples, we have studied the incoherent scattering of hydrogens in phenylene rings on the one hand, and on the other hand the coherent quasielastic scattering of all the atoms in the sample. Two different types of neutron spectrometers, time of flight and backscattering, were used in order to cover a wide dynamic range, which extends from microscopic (approximately 10(-13) s) to mesoscopic (approximately 10(-9) s) times. Moreover, neutron-diffraction experiments with polarization analysis were carried out in order to characterize the structural features, and the relative coherent and incoherent contributions of the samples investigated. In contrast with previous studies of phenylene ring dynamics in BPA polysulfone performed by us also by neutron scattering, phenylene rings in BPA PC exhibit an "extra" motion in addition to those found for BPA polysulfone's phenylene rings. This extra motion of the rings in PC perfectly correlates with the main carbonate group motion followed by dielectric spectroscopy and allows us to (i) consistently interpret the PC's gamma relaxation in terms of two different motions; and (ii) experimentally confirm the relation between the motion of phenylene rings and carbonate groups within BPA PC formerly predicted by computational methods.
我们通过准弹性中子散射研究了玻璃态双酚 A（BPA）聚碳酸酯（PC）中苯环的动力学。利用样品的选择性氘化，一方面我们研究了苯环中氢原子的非相干散射，另一方面研究了样品中所有原子的相干准弹性散射。为了覆盖从微观（约 10^(-13) s）到介观（约 10^(-9) s）时间的宽动态范围，使用了两种不同类型的中子谱仪，即飞行时间谱仪和背散射谱仪。此外，进行了带有极化分析的中子衍射实验，以表征所研究样品的结构特征以及相对相干和非相干贡献。与我们之前同样通过中子散射对 BPA 聚砜中苯环动力学的研究相比，BPA PC 中的苯环除了具有那些在 BPA 聚砜苯环中发现的运动之外，还表现出一种“额外”运动。PC 中苯环的这种额外运动与通过介电谱观察到的主要碳酸酯基团运动完美相关，并且使我们能够（i）根据两种不同运动一致地解释 PC 的γ弛豫；以及（ii）通过实验证实之前通过计算方法预测的 BPA PC 中苯环运动与碳酸酯基团运动之间的关系。
