Li Linling, Chen Jiao, Deng Weijia, Zhang Chen, Sha Ye, Cheng Zhen, Xue Gi, Zhou Dongshan
†Key Laboratory of High Performance Polymer Materials and Technology of Ministry of Education, Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, P. R. China.
‡Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters, College of Physical Science and Technology, Yili Normal University, Yining 835000, P. R. China.
J Phys Chem B. 2015 Apr 16;119(15):5047-54. doi: 10.1021/jp511248q. Epub 2015 Apr 3.
The glass transitions of poly(methyl methacrylate) (PMMA) oligomer confined in alumina nanopores with diameters much larger than the polymer chain dimension were investigated. Compared with the case of 80 nm nanopores, PMMA oligomer confined in 300 nm nanopores shows three glass transition temperatures (from from low to high, denoted as Tg,lo, Tg,inter, and Tg,hi). Such phenomenon can be interpreted by a three-layer model: there exists an interphase between the adsorbed layer and core volume called the interlayer, which has an intermediate Tg. The behavior of multi-Tg parameters is ascribed to the propagation of the interfacial interaction during vitrifaction process. Besides, because of the nonequilibrium effect in the adsorbed layer, the cooling rate plays an important role in the glass transitions: the fast cooling rate generates a single Tg; the intermediate cooling rate induces three Tg values, while the ultraslow cooling rate results in two Tg values. With decreasing the cooling rate, the thickness of interlayer would continually decrease, while those of the adsorbed layer and core volume gradually increase; meanwhile, the Tg,lo gradually increases, Tg,inter almost stays constant, and the Tg,hi value keeps decreasing. In such a process, the dynamic exchanges between the interlayer and adsorbed layer, core volume should be dominant.
研究了直径远大于聚合物链尺寸的氧化铝纳米孔中聚甲基丙烯酸甲酯（PMMA）低聚物的玻璃化转变。与80 nm纳米孔的情况相比，限制在300 nm纳米孔中的PMMA低聚物表现出三个玻璃化转变温度（从低到高，分别表示为Tg,lo、Tg,inter和Tg,hi）。这种现象可以用三层模型来解释：在吸附层和核心体积之间存在一个称为中间层的中间相，其具有中间的玻璃化转变温度。多玻璃化转变参数的行为归因于玻璃化过程中界面相互作用的传播。此外，由于吸附层中的非平衡效应，冷却速率在玻璃化转变中起着重要作用：快速冷却速率产生单一的玻璃化转变温度；中间冷却速率诱导出三个玻璃化转变温度值，而超慢冷却速率导致两个玻璃化转变温度值。随着冷却速率的降低，中间层的厚度会持续减小，而吸附层和核心体积的厚度逐渐增加；同时，Tg,lo逐渐升高，Tg,inter几乎保持不变，Tg,hi值不断降低。在这个过程中，中间层与吸附层、核心体积之间的动态交换应该占主导地位。
