Crystallization Kinetics of Crystalline–Crystalline and Crystalline–Amorphous Block Copolymers of Linear Polyethylene and Isotactic Polypropylene,Macromolecules

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Crystallization Kinetics of Crystalline–Crystalline and Crystalline–Amorphous Block Copolymers of Linear Polyethylene and Isotactic Polypropylene
Macromolecules ( IF 5.1 ) Pub Date : 2024-09-10 , DOI: 10.1021/acs.macromol.4c01402
Alessandra Cicolella _{1,

2} , Miriam Scoti ₁ , Giovanni Talarico ₁ , Alejandro J. Müller _{3,

4} , Rocco Di Girolamo ₁ , Claudio De Rosa ₁

Affiliation

Crystalline–amorphous diblock copolymers (BCPs) comprising crystalline blocks of isotactic polypropylene (iPP) or polyethylene (PE) linked to amorphous blocks of random ethylene–propylene copolymers (EPR) (iPP-b-EPR and PE-b-EPR) of different block lengths and ethylene concentrations in EPR blocks, and crystalline–crystalline BCPs composed by iPP and PE blocks (iPP-b-PE) have been synthesized with different living catalysts. The effects of the presence of a linked EPR rubbery block of varying composition on the crystallization behaviors and kinetics of PE and iPP, and of crystalline PE or iPP block on the crystallization kinetics of linked iPP or PE, respectively, have been analyzed. All samples have been isothermally crystallized from melting at different temperatures, and the crystallization kinetics have been analyzed. In iPP-b-PE BCPs, the PE block crystallizes first from the melt during nonisothermal cooling or isothermal crystallization. The iPP block crystallizes after PE and nucleates over the PE crystals. In both iPP-b-EPR and PE-b-EPR BCPs, the linked amorphous EPR block slows down the crystallization of iPP and PE blocks with respect to their respective homopolymers. Furthermore, in iPP-b-EPR samples, a higher concentration of propylene in the EPR phase results in a more significant slowdown of the crystallization kinetics of iPP due to a higher solubility between the blocks. Analogously, in PE-b-EPR copolymers, the increase in the length of the EPR block results in a more pronounced slowdown of the crystallization rate of PE with respect to the PE homopolymer due to the significant dilution exerted by the long EPR block. All samples of iPP-b-PE copolymers show crystallization rates lower than that of the PE homopolymer but faster than that of the iPP homopolymer. In isothermal crystallization experiments, the iPP blocks do not crystallize, not even at low crystallization temperatures, but crystallize upon successive cooling, nucleating over the PE crystals formed in the isothermal step. Therefore, the linked iPP, which remains in the melt during the isothermal crystallization, slows down the crystallization kinetics of PE, in contrast to what happens in a sample of iPP/PE blend, where the crystallization kinetics of PE is not affected by the presence of the phase-separated iPP.

中文翻译：

线性聚乙烯和全同立构聚丙烯的结晶-结晶和结晶-非晶嵌段共聚物的结晶动力学

结晶-无定形二嵌段共聚物（BCP）包含等规聚丙烯（iPP）或聚乙烯（PE）的结晶嵌段与不同的无规乙烯-丙烯共聚物（EPR）（iPP- b -EPR和PE -b -EPR）的无定形嵌段连接。使用不同的活性催化剂合成了 EPR 嵌段中的嵌段长度和乙烯浓度，以及由 iPP 和 PE 嵌段组成的结晶-结晶 BCP（iPP- b -PE）。分析了不同组成的连接 EPR 橡胶嵌段的存在对 PE 和 iPP 的结晶行为和动力学的影响，以及结晶 PE 或 iPP 嵌段对连接的 iPP 或 PE 的结晶动力学的影响。所有样品均在不同温度下熔融等温结晶，并分析了结晶动力学。在 iPP -b -PE BCP 中，PE 嵌段在非等温冷却或等温结晶过程中首先从熔体中结晶。 iPP 嵌段在 PE 之后结晶并在 PE 晶体上成核。在 iPP- b -EPR 和 PE -b -EPR BCP 中，连接的无定形 EPR 嵌段减慢了 iPP 和 PE 嵌段相对于其各自均聚物的结晶速度。此外，在 iPP -b -EPR 样品中，EPR 相中丙烯浓度较高，由于嵌段之间的溶解度较高，导致 iPP 结晶动力学更显着减慢。类似地，在PE- b -EPR共聚物中，由于长EPR嵌段的显着稀释作用，EPR嵌段长度的增加导致PE相对于PE均聚物的结晶速率更显着地减慢。 iPP- b -PE 共聚物的所有样品均显示出低于 PE 均聚物的结晶速率，但高于 iPP 均聚物的结晶速率。在等温结晶实验中，即使在低结晶温度下，iPP 嵌段也不会结晶，但在连续冷却时会结晶，在等温步骤中形成的 PE 晶体上成核。因此，在等温结晶过程中保持在熔体中的连接 iPP 会减慢 PE 的结晶动力学，这与 iPP/PE 共混物样品中发生的情况相反，其中 PE 的结晶动力学不受存在的影响相分离的 iPP。

更新日期：2024-09-10

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