Yan Dongpeng, Lu Jun, Wei Min, Li Hui, Ma Jing, Li Feng, Evans David G, Duan Xue
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, PR China.
J Phys Chem A. 2008 Aug 21;112(33):7671-81. doi: 10.1021/jp801922b. Epub 2008 Jul 25.
This paper describes a systematic study on the thermal polymerization of both pristine 4-vinylbenzenesulfonic anion (VBS) and intercalated VBS in the two-dimensional (2D) gallery of Ni-Al layered double hydroxide (VBS/Ni-Al-LDH), by virtue of combining experimental and theoretical investigations. In situ FT-IR, in situ high-temperature X-ray diffraction (HT-XRD), UV-vis absorption spectroscopy, TG-DTA and elemental analysis were used to study the polymerization process, and it was found that the polymerization of VBS/Ni-Al-LDH occurs at ca. 150-170 degrees C, at least 40 degrees C lower than that of the pristine VBS, indicating that the layered structure of LDH is favorable for thermal polymerization of VBS. Therefore, this layered inorganic material may have potential application as a "molecular reactor" for enhancing the efficiency of polymerization reaction. Furthermore, the sheet-like polymerization product was obtained with the LDHs lamella as template. For better understanding the structure and arrangement of intercalated VBS and the polymerization product between the layers of Ni-Al-LDH, molecular dynamics (MD) simulation method was employed. The simulation results of hydration energies show that there are two relatively stable stages upon the increase of the number of interlayer water molecules. VBS molecules exhibit a tendency from tilted to vertical orientation with respect to the layers as the interlayer water content increases. Compared with the experimental results, the calculated interlayer spacing is more severely affected by interlayer water content. Finally, a typical tetramer product of VBS intercalated LDH was studied and the simulated equilibrium interlayer spacing is consistent with the experimental result of in situ HT-XRD. Based on the combination of experimental and theoretical studies on the interlayer polymerization system, the aim of this work is to deeply investigate the differences in thermal polymerization process between pristine monomers and intercalated ones in the gallery of LDHs, and to give detailed information of the arrangement and swelling behavior of guest molecules confined between the sheets of host layers.
本文通过结合实验和理论研究，描述了对原始4-乙烯基苯磺酸阴离子（VBS）以及插层在二维（2D）镍铝层状双氢氧化物（VBS/Ni-Al-LDH）层间的VBS进行热聚合的系统研究。利用原位傅里叶变换红外光谱（FT-IR）、原位高温X射线衍射（HT-XRD）、紫外可见吸收光谱、热重-差示热分析（TG-DTA）和元素分析来研究聚合过程，发现VBS/Ni-Al-LDH的聚合发生在约150-170℃，比原始VBS的聚合温度至少低40℃，这表明LDH的层状结构有利于VBS的热聚合。因此，这种层状无机材料作为“分子反应器”提高聚合反应效率可能具有潜在应用。此外，以LDHs薄片为模板获得了片状聚合产物。为了更好地理解插层VBS以及Ni-Al-LDH层间聚合产物的结构和排列，采用了分子动力学（MD）模拟方法。水化能的模拟结果表明，随着层间水分子数目的增加，存在两个相对稳定的阶段。随着层间水含量的增加，VBS分子相对于层呈现从倾斜到垂直取向的趋势。与实验结果相比，计算得到的层间距受层间水含量的影响更大。最后，对VBS插层LDH的典型四聚体产物进行了研究，模拟得到的平衡层间距与原位HT-XRD的实验结果一致。基于对层间聚合体系的实验和理论研究相结合，这项工作的目的是深入研究原始单体和插层单体在LDHs层间热聚合过程中的差异，并给出主体层片间客体分子排列和膨胀行为的详细信息。
