Having had success depositing hexane plasma polymer films for micro- and nanofabrication applications, and also carboxyl functional groups for biomedical engineering, we are now trying to create amine functionalised surfaces by plasma polymerisation of allylamine or heptylamine.
There is a considerable amount of literature covering the deposition of functional polymer films like this, however we are having trouble with autopolymerisation of the monomer inside the chamber, creating a black sludge type substance that clogs the needle valves and speedivalves, whilst also attacking the Viton o-rings and membranes.
XPS analysis of the depositions and chemical coupling experiments show that we are creating a functional surface, however the full chamber has to be stripped down and cleaned after only a few depositions.
Can anyone offer some advice on working with these monomers in a plasma polymerisation setup?
Our chamber is homemade, using two copper band electrodes to excite the plasma, operating at 0.1mBar polymerisation pressure, 25W excitation power at 13MHz.
I think no one can help you seriously without knowing your experimental set-up in detail. As a general rule you certainly know that the external plasma parameters determine the deposition rate. So you can try to reduce the pressure and/or the gas flow rate and/or the monomer concentration in the carrier gas. Depending on reactor configuration the power could play a role. You know that the main problem in the plasma processes scale-up is that the chamber shape plays a fundamental role and no one has found a relationship between external plasma parameters, the fluidodynamic inside the chamber and the deposition rate or generally speaking the effect of plasma treatments.
PS be careful to your pumping system
i have used allylamine as monomer for plasma polymerization. however, we have not observed that autopolymerization inside the monomer chamber and your mentioned black sludge type substance. BUT allylamine will attack the Viton o-rings after a few weeks.
My suggestion: befor you add allylamine into the monomer chamber, keep it into the lowest vacuum degree. thus allylamine might not see self-reaction products.
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