Looking at the Internet available Material Studio tutorials
for polymer blends, I understand that you can simulate the blends
but the procedure does not include the polymers proportions amongst polymers.
Based on the tutorial I am interpreting that you get the Chi parameter of Flory-Huggins for a randome
mixture of polymer A and B but you still have to make MD calculations for the best mixture proportion.
Is thist correct?Reading Material Studio tutorials
Using Material Studio I understand that you can simulate polymer blends but the procedure does not include the polymers proportions amongst polymers. Based on the tutorial (pdf) I am interpreting that you get the Chi parameter of Flory-Huggins for a randome
mixture of polymer A and B but you still have to make MD calculations for the best mixture proportion. Is this correct?
I know that Flory-Huggins is still the most popular approach for polymer blends - nevertheless it is starting with a basically wrong assumption:
- that polymer blends can be described in an equilibrium thermodynamical manner.
Let us be clear first: polymer "blends" are mixtures of 2 or more polymers which are not compatible with each other, they are not polymer "alloys", not soluble within each other.
Therefore, such blends do not form "random" mixtures, but they are highly structured in a very complex way, following spontaneous self-organisation principles as usual for non-equilibrium systems far from equilibrium.
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Dear Bernhard, thank you for taking your time to contribute.
Considering your observation, I would like to include some comments.
Yes, there are limitations to Flory-Huggins equation. So, we have to work on approximations, amongst others, molecules on the entropy of mixing are neglected (random mixing) and concentration-dependence of Flory-Huggins interaction is neglected as well. I also understand that the development of such materials is largely empirical and a finer degree of control of their properties is still not plain fully achieved by in silico methods.
Changing the question: what is the quality of the results I get with in silico simulations in defining the best blends through Flory-Huggins parameter?
This information is very important before going into experiment by electrostatic spinning which will allow the production of fine polymer mixed nanofibers, which is finally the product I need for Biosensor development.
Bruno, I can not answer your modified question, but my general answer is:
One can not or should not make a complex problem apparently more simple by assuming it may behave like its own contrary. By saying "amongst others, molecules on the entropy of mixing are neglected (random mixing) and concentration-dependence of Flory-Huggins interaction is neglected as well" you neglect 2 of several basic characteristics for polymer blends,
a) the entropy flux (entropy of the polymer mixture is *decreasing" during mixing! it gets a lower value compared to the starting materials! need to be aware of this!)
b) random mixing does not occur, it is not random, not at all!
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