Crosslinking of floating colloidal monolayers

Abstract

Abstract: Crosslinked colloidal monolayers are promising as templates, lithographic masks, filtration membranes, or membranes for controlled release rates in drug delivery. We demonstrate assembly of monodisperse micron-sized polystyrene (PS) beads at an air/water interface, which are transformed into crystalline monolayers using addition of surface-active agents. Vapor annealing methods with solvents (toluene and xylene) and crosslinking agents (divinylbenzene) were investigated regarding their ability to crosslink these floating monolayers directly at the interface, generating crosslinked membranes with crystal size up to 44 cm², domain size up to 1.9 mm², and nano-sized pores (100-300 nm). The demonstrated fabrication method emphasizes short fabrication time using a simple setup.

Keywords: Annealing; Assembly; Colloids; Crystal structure; Electron microscopy; Nanostructures.

Fig. 1

a Scanning electron micrograph of PS particles, b size distribution by SEM (ImageJ, analysis of ≥900 particles), and c size distribution by DLS

Fig. 2

PS particle assembly (≈44 cm²) at the air/water interface, gently agitated at 45 rpm for 30 min and compressed by addition of Triton X-100, a light refraction of PS monolayer at the air/water interface, b laser diffraction pattern showing the high crystallinity of PS monolayer, c, d scanning electron micrographs of monolayer transferred to silicon substrate, c single crystal domain (image size: 1.9 mm²)

Fig. 3

Scanning electron micrographs for PS particle films treated by static vapor swelling, a film treated with 14 cm³ of toluene in the vapor chamber for 90 s, b, c film treated with 14 cm³ of toluene in the vapor chamber for 100 s, and d aperture size vs. exposure time with toluene vapor (aperture size and standard deviation by image analysis with ImageJ for ≥100 apertures)

Fig. 4

Scanning electron micrographs of PS particle films treated with dynamic vapor swelling (toluene) for a 30 s, b 40 s, and c aperture size vs. exposure time with toluene vapor (aperture size and standard deviation by image analysis with ImageJ for ≥100 apertures)

Fig. 5

Scanning electron micrographs of PS particle films treated with dynamic vapor swelling (xylene) for a 40 s, b 50 s, c 60 s, and d aperture size vs. exposure time with xylene vapor (aperture size and standard deviation by image analysis with ImageJ for ≥100 apertures)