Efficiently suppressing coalescence in polymer blends using nanoparticles: role of interfacial rheology
Efficiently suppressing coalescence in polymer blends using nanoparticles: role of interfacial rheology
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DOI：
10.1039/b927299b
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发表时间：
2010-07
期刊：
影响因子：
3.4
通讯作者：
Steven Vandebril;J. Vermant;P. Moldenaers
中科院分区：
文献类型：
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作者：
Steven Vandebril;J. Vermant;P. Moldenaers
两种或多种不混溶聚合物的共混是产生新材料的有吸引力的途径。然而，在液态加工过程中，由于破裂和聚结之间的复杂相互作用，流动诱导的微观结构连续变化，通常导致具有较差性能的粗糙形态。因此，产生和稳定精细形态的需要是显而易见的，并且嵌段共聚物通常用作增容剂。纳米粒子的使用已被认为是“相容化”不混溶聚合物对的替代方案。在目前的工作中，位于界面上的纳米粒子在不混溶共混物的聚结的作用进行了系统的研究，以澄清其作用相比，嵌段共聚物。一个（70/30体积%）的聚二甲基硅氧烷（PDMS）/聚异丁烯（PIB）与液滴/基体微观结构的共混物被选为模型系统。接触角测量和理论模型用于选择纳米颗粒的表面化学，以确保它们在聚合物/聚合物界面处的定位，这在低温条件下通过扫描显微镜进行实验验证。使用流变学的方法，它示出，聚结的分散相是减缓或甚至完全抑制纳米粒子存在于界面处时。当颗粒浓度增加或（聚集体）尺寸减小时，这种效果变得更强。此外，各向异性纳米粒子往往比它们的球形对应物更有效地稳定共混物。使用平面界面的光学显微镜和界面流变仪的组合已被用来证明，纳米粒子主要影响表面流变性能，而传统的增容剂也强烈影响界面张力。因此，具有合适表面化学性质的纳米颗粒可用于通过优化其浓度、尺寸和形状来调节不混溶聚合物共混物的流动诱导微观结构。
Blending of two or more immiscible polymers is an attractive route to generate new materials. However, during processing in the liquid state, the flow-induced microstructure changes continuously due to a complex interplay between break-up and coalescence, typically resulting in a coarse morphology with poor properties. Hence, the need to generate and stabilize a fine morphology is obvious and block copolymers are typically used as compatibilizers. The use of nanoparticles has been suggested to be an alternative to ‘compatibilize’ immiscible polymer pairs. In the present work, the role of interfacially located nanoparticles on the coalescence in immiscible blends is investigated systematically to clarify their role as compared to that of block copolymers. A (70/30 vol%) polydimethylsiloxane (PDMS)/polyisobutylene (PIB) blend with a droplet/matrix microstructure is chosen as a model system. Contact angle measurements and theoretical models are used to select the surface chemistry of the nanoparticles to ensure their localization at the polymer/polymer interface, which is experimentally verified by scanning microscopy under cryogenic conditions. Using a rheological method it is shown that coalescence of the dispersed phase is slowed down or even totally suppressed when nanoparticles are present at the interface. This effect becomes stronger when the particle concentration is increased or the (aggregate) size is reduced. Additionally, anisotropic nanoparticles tend to stabilize blends more efficiently than their spherical counterparts. A combination of optical microscopy and interfacial rheometry using planar interfaces has been used to demonstrate that the nanoparticles mainly affect the surface rheological properties, whereas traditional compatibilizers also strongly affect the interfacial tension. As a result, nanoparticles with a suitable surface chemistry can be used to tune the flow-induced microstructure of immiscible polymer blends by optimizing their concentration, size and shape.