School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States.
Langmuir. 2013 Aug 6;29(31):9761-9. doi: 10.1021/la401597p. Epub 2013 Jul 24.
We report the interfacial assembly of amphiphilic heteroarm star copolymers (PSnP2VPn and PSn(P2VP-b-PtBA)n (n = 28 arms)) on graphene oxide flakes at the air-water interface. Adsorption, spreading, and ordering of star polymer micelles on the surface of the basal plane and edge of monolayer graphene oxide sheets were investigated on a Langmuir trough. This interface-mediated assembly resulted in micelle-decorated graphene oxide sheets with uniform spacing and organized morphology. We found that the surface activity of solvated graphene oxide sheets enables star polymer surfactants to subsequently adsorb on the presuspended graphene oxide sheets, thereby producing a bilayer complex. The positively charged heterocyclic pyridine-containing star polymers exhibited strong affinity onto the basal plane and edge of graphene oxide, leading to a well-organized and long-range ordered discrete micelle assembly. The preferred binding can be related to the increased conformational entropy due to the reduction of interarm repulsion. The extent of coverage was tuned by controlling assembly parameters such as concentration and solvent polarity. The polymer micelles on the basal plane remained incompressible under lateral compression in contrast to ones on the water surface due to strongly repulsive confined arms on the polar surface of graphene oxide and a preventive barrier in the form of the sheet edges. The densely packed biphasic tile-like morphology was evident, suggesting the high interfacial stability and mechanically stiff nature of graphene oxide sheets decorated with star polymer micelles. This noncovalent assembly represents a facile route for the control and fabrication of graphene oxide-inclusive ultrathin hybrid films applicable for layered nanocomposites.
我们在气-液界面报告了两亲性杂臂星型嵌段共聚物（PSnP2VPn 和 PSn(P2VP-b-PtBA)n（n = 28 臂））在氧化石墨烯薄片上的界面组装。在 Langmuir 槽中研究了星型聚合物胶束在单层氧化石墨烯片的基面和边缘表面上的吸附、铺展和有序排列。这种界面介导的组装导致胶束修饰的氧化石墨烯片具有均匀的间距和有序的形态。我们发现，溶剂化氧化石墨烯片的表面活性使星型聚合物表面活性剂能够随后吸附在预悬浮的氧化石墨烯片上，从而产生双层复合物。含有杂环吡啶的带正电荷的杂臂星型聚合物对氧化石墨烯的基面和边缘表现出很强的亲和力，导致了有序和长程有序的离散胶束组装。由于臂间排斥的减少，增加的构象熵可以解释优先结合。通过控制组装参数（如浓度和溶剂极性）可以调节覆盖率。与在水面上的胶束相比，在基面的聚合物胶束在横向压缩下保持不可压缩，这是由于氧化石墨烯的极性表面上的强排斥受限臂和以片边缘形式存在的预防性障碍。明显存在密集堆积的双相平铺状形态，表明用星型聚合物胶束修饰的氧化石墨烯片具有高界面稳定性和机械刚性。这种非共价组装为控制和制造适用于层状纳米复合材料的包含氧化石墨烯的超薄混合薄膜提供了一种简单的途径。
