3
$\begingroup$

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?

|improve this question
$\endgroup$
2
$\begingroup$

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)
|improve this answer
$\endgroup$
  • $\begingroup$ 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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.