The colloidal layers have attracted much attention because of their various potential applications, such as sensors, optical devices, and data storages. Although the properties of such colloidal layers primarily depend on the layer structures as well as particle types, most colloidal layers prepared through the spontaneous bottom-up approaches have only a close-packed structure. If a colloidal layers with a constant interparticle distance, that is, a non-close-packed (NCP) structure can be fabricated, the colloidal layer properties can be controlled without changing the particle sizes and types, which leads to increasing their application possibilities.
In this work, the authors have tried to fabricate the NCP colloidal layers without using any template, by the convective self-assembly (CSA) using the polyelectrolyte-grafted silica particles: as a grafted polymers, two cationic polyelectrolytes, poly((3-acrylamidopropyl)trimethylammonium chloride) (PAPTAC) and poly(vinylbenzyl trimethylammonium chloride) (PVBTA) were employed. As a result, it was found that the CSA using PAPTAC grafted silica particles (PAPTAC-Si) gives the colloidal monolayers with a strange wiggle beads structure, while the colloidal monolayers with an NCP structure were successfully obtained by the CSA using PVBTA grafted silica particles (PVBTA-Si). It should be noted that although both PAPTAC-Si and PVBTA-Si have the cationic polyelectrolyte brushes on their surfaces, the structures of the resultant colloidal layers are quite different from each other. This demonstrate that the molecular structures of the grafted polymers have a significant influence on the colloidal layer structures prepared by the CSA process.
Journal ReferenceShow Affiliations
- Department of Chemistry and Applied Chemistry, Saga University, 1 Honjyo, Saga, 840-8502, Japan
- Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa, 226-8502, Japan
Two cationic polyelectrolytes, poly((3-acrylamidopropyl)trimethylammonium chloride) (PAPTAC) and poly(vinylbenzyl trimethylammonium chloride) (PVBTA), have been grafted on the surface of the silica particles, and then these polyelectrolyte-grafted silica particles have been applied to the convective self-assembly (CSA) process using mica substrate to prepare colloidal layers. When the PAPTAC-grafted silica particles (PAPTAC-Si) were used, we obtained the colloidal monolayers with a curious pattern composed of many wiggle beads. By the CSA process using the PVBATA-grafted silica particles (PVBTA-Si), on the other hand, we succeeded in fabricating the colloidal monolayers having a somewhat constant interparticle distance, that is, a non-close-packed (NCP) structure without using any templates. Although both particles have cationic polyelectrolytes on their surfaces, the structures of the resultant colloidal monolayers are quite different from each other, indicating that the molecular structure of the grafted polymer is crucially important for the patterning of the colloidal layers through the CSA process.Go To Colloid and Polymer Science