I want to coat glass substrates with silicone materials, but the coating does not adhere well and it removes easily. Is there any solution to improve adhesion without needing to surface treatment of the substrate, treatments like plasma etc?
I've seen something like that (I enclose a print screen) in book entitled "Handbook of Crystal Growth: Thin Films and Epitaxy". Maybe this could help you...
What is "harsh"?
In my opinion, low temperature Plasma cleaning is very gentle. Due to my personal experience, vacuum plasma may render the cleanest surface possible. But be sure that you can keep any contaminants off. If he problem is that you do not have any plasma available, I suggest to use household cleaners from the shop.
if this is not scientific enough, identify the contamination and consider some solvent rinsing or vapour cleaning.
As a commercial window cleaner, I used warm water and took efforts to remove it completely afterwards.
I concur with Mr. Gruenwald that oxygen plasma cleaning is very gentile and a much used technique to get rid of chemisorbed water and carbon on surfaces. In your case their might be a special problem. Most of the silicones contain a large amount of CH3 groups and these materials in general are hydrophobic and do not wish to attach to hydrophilic surfaces (like glass). To optimize the adhesion you could use a primer (e.g. HMDS). Primer molecules on one end attach to a hydrophilic surface and on the other end bond well to more covalent/hydrophobic molecules like PDMS. HMDS primer is a commercially available product used in the semiconductor industry but there are many variants. Be aware that long term adhesion of silicones to any surface is troublesome. Silicones behave a bit like a liquid and the molecular chains within silicones rearrange constantly and therefore wil break bonds with the surface in time. These rearrangements depend a lot on the temperature of your substrate/silicone.
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