Crupi Vincenza, Fontana Aldo, Giarola Marco, Longeville Stéphane, Majolino Domenico, Mariotto Gino, Mele Andrea, Paciaroni Alessandro, Rossi Barbara, Trotta Francesco, Venuti Valentina
Department of Physics and Earth Sciences, University of Messina , CNISM UdR Messina, Viale Ferdinando Stagno D'Alcontres 31, 98166 Messina, Italy.
J Phys Chem B. 2014 Jan 16;118(2):624-33. doi: 10.1021/jp410448y. Epub 2014 Jan 6.
The vibrational dynamics of a new class of cross-linked polymers made up of cyclodextrins is here investigated in the microscopic range by the joint use of light and inelastic neutron scattering experiments. The effect of increasing the connectivity of the polymeric network on the vibrational dynamics of the system is studied by exploiting the complementarity of these two different probes. The derived densities of vibrational states of the polymers evidence the presence of the characteristic anomalous excess of vibrational modes with respect to the Debye level, already observed in the low-frequency Raman spectra and referred to as boson peak (BP). The overall analysis of the spectra suggests an emerging picture in which the motions of hydrogen atoms of the polymers are progressively hampered when the cross-linking degree of the covalent network increases. At the same time, the frequency and intensity of the BP are found to significantly change by increasing the cross-linking degree of the polymeric network, as clearly suggested by the existence of a scaling-law for the BP evolution. These findings support the conclusion that the growing of the covalent connectivity of the system induces a general modifications of the elastic properties of these cyclodextrin-based polymers, which are, once again, modulated by the cross-linking agent/cyclodextrin molar ratio.
本文通过联合使用光散射和非弹性中子散射实验，在微观尺度上研究了一类由环糊精组成的新型交联聚合物的振动动力学。利用这两种不同探测手段的互补性，研究了增加聚合物网络连通性对系统振动动力学的影响。聚合物的振动态密度表明，相对于德拜能级，存在特征性的异常过量振动模式，这在低频拉曼光谱中已经观察到，并被称为玻色子峰（BP）。对光谱的整体分析表明，随着共价网络交联度的增加，聚合物中氢原子的运动逐渐受到阻碍。同时，发现随着聚合物网络交联度的增加，BP的频率和强度会显著变化，这由BP演化的标度律明确表明。这些发现支持了这样的结论：系统中共价键连通性的增加会引起这些环糊精基聚合物弹性性质的普遍改变，而这种改变再次由交联剂/环糊精摩尔比调节。
