Fabrication of non-close-packed colloidal monolayers by convective self-assembly using cationic polyelectrolyte-grafted silica particles

Abstract

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.

Controlling the Interaction and Non-Close-Packed Arrangement of Nanoparticles on Large Areas

“…However, structures of moderate order were limited to a few micrometers. Ordered structures on longer scales could not be achieved …”

“…Ordered structures on longer scales could not be achieved. 29 A quartz crystal microbalance with dissipation monitoring (QCM-D) is a widely used technique for studying processes at interfaces based on the piezoelectric properties of a quartz sensor. By applying an alternating electric field to an appropriately oriented quartz crystal (e.g., an AT-cut sample) a mechanical oscillation of the crystal with a characteristic resonance frequency is induced.…”

Effect of Particle–Substrate Interactions on Colloidal Layer Structure Prepared by Convective Self-Assembly Using Polyelectrolyte-Grafted Silica Particles

“…These results are almost the same as those previously obtained using the mica substrate instead of the hydrophilic glass substrate. 34 When the hydrophobic glass substrate was used, the NCP colloidal monolayers were also formed, as shown in Figure 2e−h. The NCP monolayers on the hydrophobic glass substrate had a shorter interparticle distance than that on the hydrophilic glass substrate at the same volume fraction, although the volume fraction dependence of the interparticle distance was the same as each other.…”

“…Previously, we successfully fabricated the NCP colloidal monolayers through CSA by using the silica particles grafted with cationic polyelectrolyte, poly(vinylbenzyl trimethylammonium chloride) (PVBTA), and a mica substrate. 34 However, the regularity of the particle arrays in the resultant NCP monolayers was not as high as that in the CP colloidal layers. This is probably because the electrostatic attraction acts between the positively charged PVBTA-grafted silica particle (PVBTA-Si) and the negatively charged mica substrate, which hinders the particle rearrangement on the substrate surface to form colloidal layers with high regularity.…”

Ordered non-close packed colloidal array with morphology control

“…49,50 Further, Morisada et al successfully prepared non-close packed arrays of silica colloids via convective self-assembly by grafting the particle surfaces with cationic polymers to facilitate particle-particle repulsion. 51 NCP arrays of hydrogel spheres containing a soft hydrated surface layer could be obtained even without functionalization due to the unique property of these colloidal particles which causes them to swell up in the presence of water and collapse upon air drying. 52,53 However, it can be seen from the discussion that most of the direct NCP array formation techniques are specific to some particular class of colloidal particles.…”