Melnikov Alexey P, Rosenthal Martin, Ivanov Dimitri A
Lomonosov Moscow State University, Faculty of Fundamental Physical and Chemical Engineering, GSP-1, 1-51 Leninskie Gory, Moscow, Russian Federation.
Moscow Institute of Physics and Technology (State University), Institutskiy per. 9, Dolgoprudny, Russian Federation.
ACS Macro Lett. 2018 Dec 18;7(12):1426-1431. doi: 10.1021/acsmacrolett.8b00754. Epub 2018 Nov 20.
Thermal characterization of semicrystalline polymers can constitute a difficult task due to the metastable nature of polymer crystals. It is well documented that polymer structure can reorganize during the thermoanalytical experiment. It has become also clear that thermal analysis alone cannot discriminate the reorganization processes from multiple melting events. Therefore, instead of studying the initial sample state the measurements may simply reflect the structural evolution uncontrollably occurring during the experiment. Here an original setup combining ultrafast chip calorimetry with millisecond time-resolved X-ray scattering is used to find the structural signature of the reorganization processes. The information is further used to construct the heating-rate versus crystallization-temperature reorganization (HR-CT-R) diagram. The diagram allows rationally designing thermoanalytical experiments in which one can completely exclude uncontrolled evolution of the semicrystalline structure. For a typical aromatic polyester, poly(trimethylene terephthalate), the critical heating rate above which all reorganization processes cease to exist can reach 1000 K/s and more.
由于聚合物晶体的亚稳态性质，半结晶聚合物的热表征可能是一项艰巨的任务。有充分的文献记载，聚合物结构在热分析实验过程中会发生重组。同样清楚的是，仅靠热分析无法区分重组过程和多次熔融事件。因此，测量可能无法反映初始样品状态，而只是简单地反映实验过程中不可控发生的结构演变。在此，使用一种将超快芯片量热法与毫秒级时间分辨X射线散射相结合的原始装置来寻找重组过程的结构特征。该信息进一步用于构建加热速率与结晶温度重组（HR-CT-R）图。该图允许合理设计热分析实验，在这些实验中可以完全排除半结晶结构的不可控演变。对于典型的芳香族聚酯聚对苯二甲酸丙二醇酯，所有重组过程停止存在的临界加热速率可达1000K/s及以上。
