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I've been toying with different potential recipes for DIY photoresist. My current favored design is a chemically amplified resist based on PVA (poly(vinyl alcohol)). For those who are unaware, a CAR works like this: a polymer is functionalized with a protecting group, and is mixed with a photoacid generator (PAG), which as the name suggests, generates acid upon exposure to light. The acid then cleaves the protecting group (in this case, t-Boc), rendering the polymer soluble in the developer. Basically, my question is how to functionalize PVA with the t-Boc group.

References are scant, but I did find one, which is unfortunately extremely vague. It says to react fully hydrolyzed PVA with di-tert-butyl dicarbonate (boc anhydride) and sodium hydride in N-methylpyrrolidone. However, the paper itself says that this reaction is not very predictable, and the authors are (were?) looking for better options.

Not being satisfied, I decided to lookup the reaction used for functionalizing poly(hydroxystyrene), which is the polymer used in the original CAR, APEX. Unfortunately, I wasn't really able to find anything on this either, save for even more vague references.

Anyhow, I have looked up information on how amino acids are protected with t-Boc, but the problem here is that I'm not sure if that would even work on PVA.

Does anyone have any idea how I would I go about doing this? Even more preferable would be a method not involving dangerous/explosive and for that matter, expensive substances such as Sodium hydride, or dangerous solvents (although NMP is not really that bad).

I did find one option that simply involves reacting amino acids directly with molten boc anhydride. Is it likely this procedure would work with PVA?

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Interesting, and i like the part with the photoacid.

I can't read the full details of the cited article (paywall), but since the authors aren't very pleased with the functionalization of the PVA, how about a change in the order of events:

vinyl tBOC

  1. prepare or buy the monomer (vinyl tBOC)
  2. polymerize it according to this article (or a better source)
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  • $\begingroup$ Hi! Well, I had actually read the article you just linked. The problem is that polymerizing vinyl tBOC involves some rather dangerous chemicals, and tricky things like nitrogen atmosphere. Although, I will look into it more. Thanks for the suggestion. $\endgroup$
    – krfkeith
    Jan 15 '14 at 20:58
  • $\begingroup$ My bad, I forgot that you mentioned DIY! In the lab, with a working fume hood and proper waste management (!) I would mind to give all this a try. However, I would NOT do it at home in my appartment. $\endgroup$
    – Klaus-Dieter Warzecha
    Jan 15 '14 at 21:10
  • $\begingroup$ Yes, hah, not exactly something one would want to do at home. However, slightly adjunct to this question, but I did find an interesting patent which details a non chemically amplified photoresist using PVA, that doesn't use hexavalent chromium (you can use dichromate salts to make a very simple one). $\endgroup$
    – krfkeith
    Jan 15 '14 at 21:21

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