Hello,
is there a simple method for the wet activation of polystyrene using Potassium Hydroxide or Sodium Hydroxide? For activation, I intend the addition of Carboxylic group COOH to the surface of a common ELISA plate.
Thank you.
As you know, the structure of polystyrene is -[-CH2-CH(Ph)-]-n were Ph refers to phenyl group or the aromatic ring. Benzene undergoes electrophilic aromatic substitution usually & NOT addition. The main hydrocarbon chain is activating so it will be ortho & para directing for substituents.
To simplify things, I shall give the 2 steps of converting benzene into benzoic acid:
i) Friedel-Crafts Alkylation: (catalyzed with AlCl3 or Lewis Acid)
C6H6 + R-Cl → C6H5-R (where R= alkyl group e.g. methyl, ethyl...etc.) + HCl
ii) Oxidation of the Alkylbenzene by KMnO4 :
C6H5-R + KMnO4 → C6H5-COOH + .......
The methyl group is bulky & that applies to longer R groups so they will go mostly to the para position which is opposite to the main chain.
If the reaction is done successfully, many "but not all" the pendant phenyl groups will have -COOH groups attached to them.
If carboxylated polystyrene is reacted with KOH or NaOH, then the researcher will be heading to the relatively new field of "ionomers" and this is another story!
Thank you. So if I understood, I should look for KMnO4 rather than KOH or NaOH, so I have been misled... Would you have also a protocol? Regards
Also, since this reaction is a substitution but polystyrene does not have additional groups apart from the ethyl group involved in the polymerization, would this reaction work on an ELISA plate?
I would buy the ready-made activated plates but they are expensive and I don't have fancy equipment for plasma activation etc. Plus, I am not a chemist so these reactions are beyond my comprehension...
Regards
Dear Luigi Marongiu thank you for your interesting technical question. The following article might help you in your analysis:
Immobilization Principles – Selecting the Surface for ELISA Assays
https://www.corning.com/catalog/cls/documents/application-notes/CLS-DD-AN-454.pdf
(see attached pdf file)
Dear Luigi Marongiu P.S. I'm not a specialist in the field, but I would not intend to chemically modify ELISA plates. You can easily buy "high binding" ELISA plates in which the polystyrene is already modified with carboxylic groups:
Corning® Medium and High Binding ELISA Microplates for Select Target Size Binding Assays
https://www.corning.com/media/worldwide/cls/documents/applications/CLS-AN-497%20DL.pdf
Good luck! 👍
Thank you, I know about these plates but I find them a bit expensive. If I could make them in the lab, with lower quality perhaps but lower costs... in the brochures they make it simple ("polystyrene can also be modified through chemical reactions") but I am also curious to know how they do it.
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