混溶聚合物共混纳米复合材料的结晶动力学和机械性能：线性与接枝系统,Macromolecules

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混溶聚合物共混纳米复合材料的结晶动力学和机械性能：线性与接枝系统
Macromolecules ( IF 5.1 ) Pub Date : 2022-09-02 , DOI: 10.1021/acs.macromol.2c01143
Abdullah S. Altorbaq ₁ , Husam Alkhodairi ₁ , Nicholas F. Mendez ₁ , Linda S. Schadler ₂ , Alejandro J. Müller _{3,

4} , Sanat K. Kumar ₁

Affiliation

我们系统地研究了添加未接枝的 PMMA 与二氧化硅接枝的 PMMA (PMMA- g -SiO ₂ ) 对 PEO 的结晶动力学和机械性能的影响。在接枝类似物中，PMMA 链从直径为 14 nm 的二氧化硅纳米粒子表面生长，接枝密度约为 0.42 链/nm ². PMMA 的分子量有系统地变化（20-85 kDa），并且限制程度通过改变 PEO 分数来调节。虽然未接枝和接枝系统中的 PEO 结晶度和晶体生长速率相互跟踪，但接枝系统表现出增强的结晶动力学，这很可能是因为更快的链动力学。此外，接枝系统具有更高的成核率，尤其是对于较短的 PMMA 链。结晶动力学的这些差异可能是由于二氧化硅表面附近的干刷区，其中接枝链不与基质相互渗透。在机械性能方面，两种添加剂都提高了 PEO 模量和韧性，PMMA- g -SiO ₂填充材料在较低载荷下经历脆性到韧性的转变。令人惊讶的是，这两种添加剂在影响 PEO 结晶和机械性能方面几乎没有区别——这可能是由于高接枝密度，核心有效地屏蔽了 PEO 基质。

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Crystallization Kinetics and Mechanical Properties of Miscible Polymer Blend Nanocomposites: Linear versus Grafted Systems

We systematically investigate the effects of adding ungrafted PMMA versus silica-grafted PMMA (PMMA-g-SiO₂) on the crystallization kinetics and the mechanical properties of PEO. In the grafted analogue, PMMA chains were grown from the surface of 14 nm diameter silica nanoparticles at a grafting density of ∼0.42 chain/nm². The molecular weight of the PMMA was varied systematically (20–85 kDa), and the extent of confinement was regulated by varying the PEO fraction. While the PEO crystallinity and the crystal growth rate in the ungrafted and grafted systems track each other, the grafted systems exhibit enhanced crystallization kinetics, most likely because of faster chain dynamics. Additionally, the grafted systems have higher nucleation rates, especially for shorter PMMA chains. These differences in crystallization kinetics are likely due to the dry-brush zone near the silica surface, where graft chains do not interpenetrate with the matrix. In the context of mechanical properties, both additives enhance the PEO modulus and toughness, with the PMMA-g-SiO₂ filled materials undergoing their brittle-to-ductile transition at lower loadings. Surprisingly, there is little difference between the two additives in how they affect PEO crystallization and mechanical properties─this is likely due to the high grafting densities where the core is effectively shielded from the PEO matrix.

更新日期：2022-09-02

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