I want to assemble uniform monolayer of polystyrene spheres of large diameter through dip coating process. I have tried it with concentration of 0.25 wt% (as I have to deal with low concentration) but was unsuccessful. Can anyone suggest me the concentration of PS, withdrawal speed, immersion time and the number of cycles to use.
I don't think you will have any luck dip coating unless you control the surface pressure using something like a Langmuir-Blodgett trough. Monodisperse spheres will naturally assemble into hexagonal arrays if the solution is cast horizontally, but only in regions. It's not easy to get a uniform coating.
https://en.wikipedia.org/wiki/Langmuir%E2%80%93Blodgett_trough
Thank you sir for providing the information. I will try to look for Langmuir-Blodgett trough but isn't that the withdrawal speed plays the role in forming monolayer and we can optimize it to get a uniform layer.
Megha,
To perform a uniform monolayer on top of your sub-phase (mostly used water for polystyrene beads) you need to monitor surface pressure and try to measure the isotherm for the polystyrene beads you are using (this will be different for various MW). Normally solid monolayer will perform on a surface pressure (SP) around 30-40 mN/m. Then for deposition, start to draw your substrate on a constant SP that you are sure one single monolayer is performed. A Langmuir-Blodget Trough can do all of these for you.
Looking the literature I believe you need to use a higher concentration (10% solid concentration). Many use centrifuge to reach to higher concentrations.
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