Rheological Properties of ABA-Type Copolymers Physically End-Cross-Linked by Polyoxometalate,Macromolecules

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Rheological Properties of ABA-Type Copolymers Physically End-Cross-Linked by Polyoxometalate
Macromolecules ( IF 5.1 ) Pub Date : 2020-12-03 , DOI: 10.1021/acs.macromol.0c01817
Qingbin He _{1,

2} , Yanjie Zhang _{1,

2} , Haolong Li ₃ , Quan Chen _{1,

2}

Affiliation

In this study, we designed an ABA-type copolymer physically end-cross-linked by polyoxometalate and developed a versatile and robust pathway to tune its structural and rheological properties. The copolymer precursors are composed of a central poly(n-butyl acrylate) (nBA) block with DP ≅ 100 and two short vinyl imidazole (VIm) moieties as chain ends. Phase segregation occurs gradually for the precursors with an increase of the number of VIm per end, N_VIm, from 1 to 7.6, and clear segregation is observed for precursor with the highest N_VIm = 7.6, using small-angle X-ray scattering. For those precursors having N_VIm ≤ 4.6, introduction of a small amount of silicotungstic acid, H₄[SiW₁₂O₄₀], induces phase segregation, owing to a strong electrostatic attraction between [SiW₁₂O₄₀]^4– ion and protonated VIm monomer. As a result, the copolymer chains are physically cross-linked, forming thermoplastic copolymers, for which the size of core, plateau modulus, and solid-to-liquid transition temperature can be tuned in wide ranges by the content of silicotungstic acid. The solid-to-liquid transition temperature is controlled by an energy barrier for dissociation of the VIm end moieties. Analysis of the solid-to-liquid transition temperature enables us to determine a scaling relationship between the energy barrier and the size and degree of protonation of the end moiety. The near-proportionality between the activation energy E_a and the length of the end moiety suggests a strong motional coupling of the ionic associations belonging to the same end moiety.

中文翻译：

多金属氧酸酯物理端交联的ABA型共聚物的流变性能

在这项研究中，我们设计了一种由多金属氧酸盐进行物理端交联的ABA型共聚物，并开发了一种通用且稳定的途径来调节其结构和流变性能。共聚物的前体由一个中心的聚丙烯酸正丁酯（n BA）嵌段和DP block 100和两个短的乙烯基咪唑（VIm）部分作为链端组成。对于前体，相分离逐渐发生，每端VIm的数量N _VIm从1增加到7.6，并且使用小角度X射线散射观察到最高N _VIm = 7.6的前体发生清晰的分离。对于那些具有N _VIm的前体≤4.6 ，由于[SiW ₁₂ O ₄₀ ] ^{4 –}之间的强静电吸引，引入少量硅钨酸H ₄ [SiW ₁₂ O ₄₀ ]引起相偏析离子和质子化的VIm单体。结果，共聚物链被物理交联，形成热塑性共聚物，对于它们，可以通过硅钨酸的含量在大范围内调节核的大小，平稳模量和固液转变温度。固-液转变温度由用于VIm末端部分解离的能垒控制。固液转变温度的分析使我们能够确定能垒与末端部分的大小和质子化程度之间的比例关系。活化能E _a与末端部分的长度之间的比例接近表明属于同一末端部分的离子缔合的强烈运动耦合。

更新日期：2020-12-22

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