Chain Entanglements and Interlamellar Links in Isotactic Polybutene-1: The Effect of Condis Crystals and Crystallization Temperature,Macromolecules

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Chain Entanglements and Interlamellar Links in Isotactic Polybutene-1: The Effect of Condis Crystals and Crystallization Temperature
Macromolecules ( IF 5.1 ) Pub Date : 2022-06-22 , DOI: 10.1021/acs.macromol.2c00460
Yanan Qin _{1,

2} , Wenbo Song ₃ , Ming Chen ₃ , Victor Litvinov _{1,

4} , Yongfeng Men _{1,

2}

Affiliation

Chain entanglements, which reside in the amorphous phase of semicrystalline polymers, influence many macroscopic properties of polymers. There are different opinions about the role of crystallization and subsequent melting in the entanglement density. Isotactic polybutene-1 (iPB-1) was selected for this study. Crystallization of this polymer from an equilibrated melt led to the formation of conformationally disordered (condis) form II crystals with high chain mobility enabling long-range chain diffusion, which facilitates chain disentangling. After the crystallization was accomplished, the entanglement network was frozen during the phase transition to stable form I with the polymer backbone fixed in the crystals. All experiments were performed for samples with form I crystals. A significant decrease in the entanglement density occurred during slow crystallization of iPB-1 with M_w = 115 kg/mol. The disentangling degree was lower at faster crystallization and for iPB-1 with a higher molecular weight M_w = 711 kg/mol. The entanglement density increased during melting and approached its equilibrium value at the end of melting. The estimated entanglement density of the equilibrated iPB-1 melt coincided within approximately 8% with the value reported in a rheological study. In addition to the entanglement density, the relative density of chain segments, which are anchored to crystallites and form interlamellar links, was estimated. The density was found to increase with increasing molecular weight, and it was larger at a faster crystallization rate due to thinner lamellae and a smaller long period on the periodic lamellar structure.

中文翻译：

等规聚丁烯 1 中的链缠结和层间链接：Condis 晶体和结晶温度的影响

存在于半结晶聚合物的无定形相中的链缠结会影响聚合物的许多宏观性质。关于结晶和随后的熔化在缠结密度中的作用有不同的看法。本研究选择全同立构聚丁烯-1 (iPB-1)。这种聚合物从平衡的熔体中结晶导致形成具有高链迁移率的构象无序 (condis) 型 II 晶体，从而实现长程链扩散，从而促进链解缠结。结晶完成后，纠缠网络在相变过程中被冻结成稳定的 I 型，聚合物骨架固定在晶体中。所有实验均针对具有 I 型晶体的样品进行。M _w = 115 千克/摩尔。在较快的结晶和具有较高分子量M _w = 711 kg/mol 的 iPB-1 下，解缠结程度较低。缠结密度在熔化过程中增加，并在熔化结束时接近其平衡值。估计的平衡 iPB-1 熔体的缠结密度与流变研究中报告的值在大约 8% 范围内一致。除了缠结密度之外，还估计了锚定在微晶上并形成层间链接的链段的相对密度。发现密度随着分子量的增加而增加，并且由于更薄的片晶和周期性片状结构上的更小的长周期，它在更快的结晶速率下更大。

更新日期：2022-06-22

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