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I am working with a commercial monomer (monomethacryloxypropyl terminated polydimethylsiloxane) with an inhibitor of BHT @1%.

I need to remove it for making an ATRP reaction. What is the good way to do this?

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  • $\begingroup$ What monomer? And what are your ideas? $\endgroup$ – Mithoron Oct 20 '17 at 13:55
  • $\begingroup$ MCR-M11 from gelest $\endgroup$ – velleda Oct 20 '17 at 13:57
  • $\begingroup$ I first tried to do it with basic alumina column, but I still have some traces.. $\endgroup$ – velleda Oct 20 '17 at 13:57
  • $\begingroup$ Picture was too big and non-googlable. It may be difficult to don't have traces, dunno what you could do. $\endgroup$ – Mithoron Oct 20 '17 at 14:08
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The BHT is only present to prevent small amounts of potential radicals polymerising the monomer. One option is to simply consume it i. e. Put in one extra per cent of your initiator. Otherwise, similarly to basic alumina, use a basic resin. Once you consume the BHT, your monomer is prone to polymerisation, so you may need to run it into your reactor under your reaction conditions e.g. flushed with nitrogen, pre-cooled, etc

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For such a large macromonomer, it would be wise to dilute it before removing BHT. A good option would be dissolving your PDMS-methacrylate in DCM and flush it through a basic alumina column. You should be able to see a slight color change on the top of the column which is the captured phenolate.

The solution provided by Beerhunter does not work for ATRP, although it is typical for conventional radical polymerization. The reason here is that you do not have control when the hydrogen transfer from BHT to your radical chain ends happens. If you use an extra amount of initiator (e.g. alkyl bromide) in your reaction, you are most likely obtaining polymers with a broad molecular weight distribution due to termination by BHT at various stages of the reaction.

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