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Thread: How to evaporate solution?

  1. #1 How to evaporate solution? 
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    Hi,

    I am spincoating some pdms with solution on some samples. However my mixture of pdms and THF is causing bubbles on the surface after spinning.
    I would like to evaporate the THF before spinning since its very important that the surface is smooth. Any idea of how to do this without curing the mixture?

    I have tried heating the pdms and THF before spinning in 45 degrees for 10-20 min, but I am still seeing bubbles. My spinning times are several minutes at thousands of rpm.

    Many thanks for any input!


    Last edited by Hologram; December 4th, 2013 at 03:36 AM.
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  3. #2  
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    I would like to know what do you refer to as pdm. Then maybe I'll be able to help you.


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  4. #3  
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    Quote Originally Posted by ankit7540 View Post
    I would like to know what do you refer to as pdm. Then maybe I'll be able to help you.
    I was referring to PDMS (Polydimethylsiloxane).
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  5. #4  
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    Ok, I get it that that you have polymeric organosilicon based compounds(s) and you have THF with it. You wanna remove the THF without any harm to the PDMS.

    .You can use a rotatory evaporator working with a vacuum pump to remove the THF. In a round bottom flask you keep your material, which is dipped in a water bath. You carefully use the vaccum pump to reduce the pressure inside the round botton flask and a mildly heat the water (in the bath ~34-39 C). Do not increase the temp too much. THF is explosive and catches fire easily. Within some minutes you will get the PDMS free of any THF.
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  6. #5  
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    Thank you for you quick reply. =)

    If you don't have a rotatory evaporator, is it enough to place it in a bath in a container which is vacuum pumped?
    What is the reason you place it in water?

    I am usually degassing the PDMS.. I can see its bubbling as pressure goes down,.. however it doesn't seem to remove all THF from the PDMS.
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  7. #6  
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    An air sealed bath connected with a vacuum pump will do. We place the flask/container in a water bath for controlled uniform heating.
    For your situation I think mild heating while degassing (using a vacuum pump) will do and may be you should shake your material properly after few minutes so that all THF evaporates. You can try to heat the bath by a hair drier or something.
    THF is volatile and will go off at around 30-40C at reduced pressure. (It boils at 66C)
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