Krestov Institute of Solution Chemistry , Russian Academy of Sciences , Akademicheskaya ul. 1 , Ivanovo 153045 , Russia.
Shubnikov Institute of Crystallography, Federal Scientific Research Center "Crystallography and Photonics", Russian Academy of Sciences , Leninskii pr. 59 , Moscow 119333 , Russia.
J Phys Chem B. 2019 Dec 12;123(49):10533-10546. doi: 10.1021/acs.jpcb.9b07475. Epub 2019 Nov 25.
An experimental phase diagram of the isotactic polypropylene-camphor system is constructed using an original optical method. It considerably deviates from the dynamic diagram, which can be obtained using conventional differential scanning calorimetry (DSC), and contains an additional boundary line that describes camphor solubility in the polymer. An accurate phase diagram makes it possible to perform a detailed and consistent thermodynamic analysis of the DSC, optical, and scanning electron microscopy data on the cooling of prehomogenized mixtures of different compositions, which leads to the formation of capillary-porous bodies via thermally induced phase separation. The removal of camphor results in the formation of polypropylene membranes, the morphology and functional properties of which, such as the total pore volume, mean pore size, permeability coefficient, and breaking stress, appear to be highly dependent on the composition of the initial binary system. It is shown that thermally induced phase separation induces the formation of microscopic cracks in the studied membranes. The crack density decreases with the polymer content in the initial system, but at 53 wt % of polypropylene, the membrane becomes completely impermeable to isopropanol despite the presence of large ∼4 μm pores, thus questioning the perspectives of its practical use. In general, the study makes it possible to achieve a deeper understanding of the membrane formation process via thermally induced phase separation in the mixtures of semicrystalline polymers with low molar mass substances.
采用原创光学方法构建了等规聚丙烯-樟脑体系的实验相图。它与使用传统差示扫描量热法（DSC）获得的动态图有很大的偏差，并且包含了一条额外的边界线，描述了樟脑在聚合物中的溶解度。准确的相图使得对预均化的不同组成混合物的冷却的 DSC、光学和扫描电子显微镜数据进行详细和一致的热力学分析成为可能，这导致通过热诱导相分离形成毛细管多孔体。樟脑的去除导致聚丙烯膜的形成，其形态和功能特性，如总孔体积、平均孔径、渗透系数和断裂应力，似乎高度依赖于初始二元体系的组成。结果表明，热诱导相分离会在研究的膜中形成微观裂纹。随着初始体系中聚合物含量的增加，裂纹密度降低，但在聚丙烯含量为 53wt%时，尽管存在大的约 4μm 孔，但膜对异丙醇完全不可渗透，这使得其实际应用前景受到质疑。总的来说，该研究使得通过低摩尔质量物质的半结晶聚合物混合物的热诱导相分离来深入了解膜形成过程成为可能。
