Stability of particle dispersion and heterogeneous interfacial layers in polymer nanocomposites
Stability of particle dispersion and heterogeneous interfacial layers in polymer nanocomposites
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DOI：
10.1016/j.polymer.2021.123813
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发表时间：
2021-04
期刊：
影响因子：
4.6
通讯作者：
Chen Gong;D. Weiblen;D. Rende;Pinar Akcora;R. Ozisik
中科院分区：
文献类型：
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作者：
Chen Gong;D. Weiblen;D. Rende;Pinar Akcora;R. Ozisik
在一项突破性的研究中，Akcora小组已经表明，具有动态不对称、异质界面的聚（环氧乙烷）、PEO、纳米复合材料在吸附聚合物的玻璃化转变温度以上呈现出独特且可逆的热硬化行为（Senses，E.例如，ACS应用材料Interfaces2015，7，14682 - 14689.）。然而，在连续聚合物工艺中常见的严重剪切场下，化学非均质界面可能是脆弱的。目前的研究受到Akcora集团在热硬化聚合物纳米复合材料方面所做工作的启发，旨在了解连续加工操作（如挤出）对热硬化纳米复合材料的结构和性能的影响。通过热重分析（TGA）、扫描电子显微镜（SEM）、小角和广角X射线散射、衰减全反射-傅里叶变换红外（ATR-FTIR）和流变仪研究了加工对PEO和胶体二氧化硅（SiO2）纳米复合材料的影响。当前研究中使用了三种类型的二氧化硅纳米颗粒（同时保持平均二氧化硅纳米颗粒尺寸和浓度恒定：40 - 50纳米直径和30%重量）：裸二氧化硅、吸附聚碳酸酯（PC）的二氧化硅和吸附聚（2-乙烯基吡啶）的二氧化硅，P2 VP。PC和P2VP到二氧化硅上的吸附产生动态不对称的非均质界面，其与其中纳米颗粒表面用小化学基团或用长接枝链化学改性的均质界面相比是相当不同的。结果表明，在挤出时，二次附聚物的平均尺寸保持不变或略微减小，但附聚量增加，导致二氧化硅纳米颗粒分散和粘弹性性能（在低于吸附聚合物的玻璃化转变温度的温度下）劣化。在所研究的三个系统中，P2VP吸附的含二氧化硅的样品在挤出时表现出最大的粘弹性能降解，这是由于在异质界面内的解吸和解缠结或团聚导致由纳米颗粒和聚合物桥形成的团聚结构的断裂。
In a groundbreaking study, Akcora group has shown that poly(ethylene oxide), PEO, nanocomposites with dynamically asymmetric, heterogeneous interfaces present a unique and reversible thermal-stiffening behavior above the glass transition temperature of the adsorbed polymer (Senses, E. et al.,ACS Appl. Mater. Interfaces2015,7, 14682–14689.). However, chemically heterogeneous interfaces can be fragile under severe shear fields that are common in continuous polymer processes. The current study is inspired by the work done in Akcora group on thermally-stiffening polymer nanocomposites and is aimed at understanding the effect of continuous processing operations such as extrusion on the structure and properties of thermally-stiffening nanocomposites. The effect of processing on nanocomposites of PEO and colloidal silica, SiO2, were investigated via thermogravimetric analysis (TGA), scanning electron microscopy (SEM), small and wide angle X-ray scattering, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and rheometry. Three types of silica nanoparticles were employed in the current study (while keeping the average silica nanoparticle size and concentration constant: 40–50 nm diameter and 30% by weight): bare silica, silica adsorbed with polycarbonate (PC), and silica adsorbed with poly(2–vinyl pyridine), P2VP. The adsorption of PC and P2VP onto silica creates a dynamically asymmetric, heterogeneous interface that is quite different compared to homogeneous interfaces where either nanoparticle surfaces are chemically modified with small chemical groups or with long grafted chains. The results indicated that upon extrusion, the average size of secondary agglomerates either remained unchanged or decreased slightly but the amount of agglomeration increased leading to deterioration of silica nanoparticle dispersion and viscoelastic properties (at temperatures below the glass transition temperature of the adsorbed polymer). Among the three systems studied, P2VP-adsorbed silica containing samples showed the largest degradation of viscoelastic properties upon extrusion, which was attributed to the desorption and disentanglement within the heterogeneous interface or to agglomeration leading to breaking of the percolated structure formed by nanoparticles and polymer bridges.