Matxinandiarena Eider, Múgica Agurtzane, Zubitur Manuela, Ladelta Viko, Zapsas George, Cavallo Dario, Hadjichristidis Nikos, Müller Alejandro J
POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, University of the Basque Country UPV/EHU, Paseo Manuel Lardizábal 3, 20018 Donostia-San Sebastián, Spain.
Department of Chemical and Environmental Engineering, University of the Basque Country UPV/EHU, Plaza Europa 1, 20018 Donostia-San Sebastián, Spain.
Polymers (Basel). 2021 Sep 16;13(18):3133. doi: 10.3390/polym13183133.
The morphology and crystallization behavior of two triblock terpolymers of polymethylene, equivalent to polyethylene (PE), poly (ethylene oxide) (PEO), and poly (ε-caprolactone) (PCL) are studied: PE--PEO--PCL (T1) and PE--PEO--PCL (T2) (superscripts give number average molecular weights in kg/mol and subscripts composition in wt %). The three blocks are potentially crystallizable, and the triple crystalline nature of the samples is investigated. Polyhomologation (C1 polymerization), ring-opening polymerization, and catalyst-switch strategies were combined to synthesize the triblock terpolymers. In addition, the corresponding PE--PEO diblock copolymers and PE homopolymers were also analyzed. The crystallization sequence of the blocks was determined via three independent but complementary techniques: differential scanning calorimetry (DSC), in situ SAXS/WAXS (small angle X-ray scattering/wide angle X-ray scattering), and polarized light optical microscopy (PLOM). The two terpolymers (T1 and T2) are weakly phase segregated in the melt according to SAXS. DSC and WAXS results demonstrate that in both triblock terpolymers the crystallization process starts with the PE block, continues with the PCL block, and ends with the PEO block. Hence triple crystalline materials are obtained. The crystallization of the PCL and the PEO block is coincident (i.e., it overlaps); however, WAXS and PLOM experiments can identify both transitions. In addition, PLOM shows a spherulitic morphology for the PE homopolymer and the T1 precursor diblock copolymer, while the other systems appear as non-spherulitic or microspherulitic at the last stage of the crystallization process. The complicated crystallization of tricrystalline triblock terpolymers can only be fully grasped when DSC, WAXS, and PLOM experiments are combined. This knowledge is fundamental to tailor the properties of these complex but fascinating materials.
研究了两种聚亚甲基三嵌段三元共聚物的形态和结晶行为，这两种共聚物分别相当于聚乙烯（PE）、聚环氧乙烷（PEO）和聚ε-己内酯（PCL）：PE--PEO--PCL（T1）和PE--PEO--PCL（T2）（上标给出以kg/mol为单位的数均分子量，下标给出以wt%为单位的组成）。这三个嵌段都具有潜在的结晶性，并且对样品的三晶性质进行了研究。通过将聚同系化（C1聚合）、开环聚合和催化剂切换策略相结合来合成三嵌段三元共聚物。此外，还对相应的PE--PEO二嵌段共聚物和PE均聚物进行了分析。通过三种独立但互补的技术确定了嵌段的结晶顺序：差示扫描量热法（DSC）、原位小角X射线散射/广角X射线散射（SAXS/WAXS）和偏光光学显微镜（PLOM）。根据小角X射线散射结果，这两种三元共聚物（T1和T2）在熔体中呈弱相分离状态。差示扫描量热法和广角X射线散射结果表明，在这两种三嵌段三元共聚物中，结晶过程均始于PE嵌段，接着是PCL嵌段，最后是PEO嵌段。因此得到了三晶材料。PCL嵌段和PEO嵌段的结晶是重合的（即相互重叠）；然而，广角X射线散射和偏光光学显微镜实验能够识别这两种转变。此外，偏光光学显微镜显示PE均聚物和T1前体二嵌段共聚物具有球晶形态，而在结晶过程的最后阶段，其他体系呈现出非球晶或微球晶形态。只有将差示扫描量热法、广角X射线散射和偏光光学显微镜实验结合起来，才能全面掌握三晶三嵌段三元共聚物复杂的结晶过程。这些知识对于定制这些复杂但迷人的材料的性能至关重要。
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