Kinetic Control of Graphene Localization in Co-continuous Polymer Blends via Melt Compounding
Kinetic Control of Graphene Localization in Co-continuous Polymer Blends via Melt Compounding
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DOI：
10.1021/acs.langmuir.7b03085
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发表时间：
2018-01-23
期刊：
影响因子：
3.9
通讯作者：
Macosko, Christopher W.
中科院分区：
文献类型：
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作者：
Bai, Lian;Sharma, Radhika;Macosko, Christopher W.
石墨烯在共连续聚合物共混物中的选择性定位是制备导电聚合物复合材料的一种有吸引力的方法。石墨烯在两个聚合物相之间的界面处的定位在超低浓度下产生良好的导电性。虽然石墨烯定位最终取决于热力学因素，如石墨烯和两种聚合物组分的表面能，但动力学也强烈影响熔融配混期间聚合物共混物中石墨烯的迁移和定位。然而，很少有研究系统地研究动力学对石墨烯局域化的重要作用。在此，我们将石墨烯纳米片（GNP）引入聚乳酸（PLA）/聚苯乙烯（PS）共连续聚合物共混物中。虽然GNP在热平衡中更喜欢PS相，但我们能够通过控制熔融配混序列、混合时间和剪切速率在聚合物共混物的界面处动力学地捕获GNP。利用形态学，流变学和电学测量，我们验证了石墨烯的本地化和抑制在退火过程中的共连续聚合物共混物的粗化。当GNP在与PS相混合之前与热稳定性较差的PLA相预混合时，GNP可以在熔融配混期间动力学地捕获在界面处。此外，我们表明，较短的熔融复合时间引起更高的GNP界面覆盖率和更有效的形态稳定效果。具有低至0.5wt%GNP且仅30秒熔融配混的共混物具有类似于10（-6）S/cm的室温电导率，这大于具有较长熔融配混时间的共混物并且潜在地可用于抗静电材料。本工作对石墨烯局域化动力学的深入研究为聚合物共混体系中片状纳米填料局域化的动力学控制提供了一般性指导。我们的研究还展示了一种制造具有低逾渗阈值的导电聚合物共混物的简便方法。
Selective localization of graphene in co-continuous polymer blends is an attractive method for preparing conductive polymer composites. Localization of graphene at the interface between the two polymer phases produces good conductivity at ultra-low concentrations. Although graphene localization is ultimately dependent on thermodynamic factors such as the surface energy of graphene and the two polymer components, kinetics also strongly affects the migration and localization of graphene in polymer blends during melt compounding. However, few studies have systemically investigated the important role of kinetics on graphene localization. Here, we introduced graphene nanoplatelets (GNPs) in polylactic acid (PLA)/polystyrene (PS) co-continuous polymer blends. Although GNPs in thermal equilibrium prefer the PS phase, we were able to kinetically trap GNPs at the interface of polymer blends via control of melt-compounding sequences, mixing times and shear rates. Utilizing morphological, rheological, and electrical measurements, we verified graphene localization and the suppression of coarsening in co-continuous polymer blends during annealing. When GNPs were premixed with the thermodynamically less-favorable PLA phase before mixing with the PS phase, GNPs can be kinetically trapped at the interface during melt compounding. Moreover, we show that a shorter melt-compounding time gives rise to a higher GNP interfacial coverage and a more effective morphology stabilization effect. Blends with as low as 0.5 wt% GNPs with only 30 s of melt compounding have a room-temperature conductivity of similar to 10(-6) S/cm, which is larger than blends with longer melt-compounding times and potentially useful for antistatic materials. The in-depth study on the kinetics of graphene localization in our work provides a general guideline for the kinetic control of the localization of platelike nanofillers in polymer blends. Our study also demonstrates a facile method for manufacturing conductive polymer blends with low percolation thresholds.