PTFE and PVDF (durapore) are both used in protein binding filter membranes (Millipore specifically). Chemically speaking the two polymers differ quite significantly due to the additional fluorides and molecular weight. Their protein-binding properties also differ. I'm curious about how the chemical differences affect their properties as a membrane material.

From what I understand, the durability between the two is quite different. The PTFE membranes are used for the filtration of organic solvents where as the PVDF membranes are generally for low protein binding. Furthermore the PTFE membranes typically require a polyethylene support.

I don't believe that the degree of polymerization or the architecture; if we were dealing with a copolymer I expect differently. Based on my molecular intuition, I would imagine that this is completely based on the chemistry of repeat unit.

My question concerns a few things. What makes the PTFE a better solvent resistant polymer? The other is how does the reduced number of fluroides result in reduced protein binding?

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  • $\begingroup$ @CHM, I don't understand how you can constantly ask this simple question and how often I have to clarify. Protein Binding Membrane. I think that's pretty straightforward $\endgroup$ – bobthejoe Jun 27 '12 at 21:35
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    $\begingroup$ Alright. From the standpoint of polymer chemistry, your question is vague. We could compare the physical properties of the bulk polymers: glass transition temperature, melting point, shear/young's modulus, crystallinity, etc. Or we could (more to the point) compare two different membranes, that have been processed differently and made from different polymers with known physical properties. How big are the holes in your membrane? Is the PVDF very regioregular? I just want you to narrow your question. $\endgroup$ – CHM Jun 27 '12 at 23:46
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    $\begingroup$ I won't be able to answer this question, but I agree that it's not yet specific enough. When you say reliability, what properties are you concerned about? And simply identifying teflon and PVDF isn't quie enough; what is the degree of polymerization of the two samples? Polydispersity index? What is the context in which you are using the membrane? $\endgroup$ – Colin McFaul Jun 28 '12 at 17:17
  • $\begingroup$ Is protein binding really that complicated of a concept? For high-throughput screens, common assays would be to use these type of filterplates for protein binding. However, the hydrophobicities of two different yet similar molecules are drastically different. The hydrophobicity of polymers are independent of the PDI. $\endgroup$ – bobthejoe Jun 30 '12 at 3:16
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    $\begingroup$ bobthejoe, I see that you've been trying very hard to make this answerable, and the two remaining comments are giving you some guidelines as to specifics that should be in the question. I'm not sure how to help the two parties meet here, though. As I had mentioned in chat to @CHM, I think that perhaps guiding your definitions for 'wetting' and 'durability' might help the polymer camp better meet your needs in terms of physical properties. I understand your frustration, but keep at it a bit and I think you will get the answer you are looking for. $\endgroup$ – jonsca Jul 1 '12 at 22:49

Essentially you are asking why about the different surface properties of PTFE vs. PVDF. Generally PTFE is more 'non stick' than PVDF, which is more non-stick than polyethene (PE). PTFE is much more chemically resistant to corrosion than PVDF or PE. You are correct to look at the chemical structure. The more Fluorine atoms on the backbone, the more proteins will not be able to chemically latch onto the surface. Measuring things like contact angle will confirm this. I don't know how much the pore structure of the membranes affect things, but from a chemical standpoint, there are clear differences.

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