From dots to doughnuts: Two-dimensionally confined deposition of polyelectrolytes on block copolymer templates

Abstract

The combination of block copolymer templating with electrostatic self-assembly provides a simple and robust method for creating nano-patterned polyelectrolyte multilayers over large areas. Understanding the deposition of the first polyelectrolyte layer is crucial for achieving successful buildup of patterned multilayers. Here, we focus on two-dimensionally confined "dots" patterns afforded by block copolymer films featuring hexagonally-packed cylinders that are oriented normal to the substrate. Rendering the cylinder caps positively charged enables the selective deposition of negatively charged polyelectrolytes on them under salt-free conditions.The initially formed polyelectrolyte nanostructures adopt a toroidal ("doughnut") shape, which results from retraction of dangling polyelectrolyte segments into the "dots" upon drying. With increasing exposure time to the polyelectrolyte solution, the final shape of the deposited polyelectrolyte transitions from a doughnut to a hemisphere. These insights would enable the creation of patterned polyelectrolyte multilayers with increased control over adsorption selectivity of the additional incoming polyelectrolytes.

Electrically Responsive, Nanopatterned Surfaces for Triggered Delivery of Biologically Active Molecules into Cells

“…The first relates to our previous observation that polyelectrolytes deposited over the interface between the PS and xP2VP domains fold back onto the xP2VP domains during the drying stage. 16,17,19 This possibly helps in encapsulating the adsorbed Dox molecules within the PEM and retaining them for prolonged times. The second explanation relates to the possible leakage of the Dox from defect points in the PEM caused by dust particles.…”

“…Recently, Shenhar and co-workers have demonstrated the utilization of surface patterns made of polystyrene- block -poly­(2-vinyl pyridine) (PS- b -P2VP) for the assembly of nanopatterned PEMs. − In this approach, the P2VP domains are cross-linked after the formation of the surface pattern by reaction of the pyridine units with 1,4-diiodobutane (DIB), which also quaternizes the pyridines. This treatment renders the cross-linked P2VP domains (denoted as “xP2VP” hereafter) positively charged and hence amenable for layer-by-layer assembly of polyelectrolytes.…”

Editorial: Self-assembly

“…By depositing negatively charged polyelectrolytes into the positively charged cylinder gaps of two-dimensionally confined "dots" pattern -built by hexagonally-packed cylinder block copolymer films -Müller, Shenhar and coworker were able to produce polyelectrolyte nanostructures that adopted a toroidal ("doughnut") shape, that eventually, after increased exposure time to the polyelectrolyte solution, reached the final shape of the deposited polyelectrolyte transitions from a doughnut to a hemisphere. The reported results could lead a way to advanced patterned multilayers that can be used in smart coating systems [22].…”