The Flory-Huggins theory describing polymer-solvent mixtures is presented. This video replaces a previous version which suffered from strange sound effects.
This is such a great explanation of the Flory-Huggins theory. I am a Chemical Engineering student in my final year and have been doing Polymer Physics research with my professor for the last few years. I remember when I first started in the research group, I looked up this video because we were working on a polymer phase separation problem and I wanted to understand what was happening. I remember not understanding anything in the video. Now three years later, I watched your video again with a much more mature understanding of thermodynamics and stat mech and I understood everything you are saying. All in all I just want to say that I really appreciate the way you explained these difficult concepts.
Thank you very much for this detailed derivation. It helps me to understand the assumption and steps which were made for this model. I like to point out that by summing over all possible solution configurations, also configurations are included which are separated and near separated configurations. This raises the question whether these configurations are allowed ? It seems to me that some of the configurations are not equilibrium configurations and therefore not allowed to be included. That is to say, the system is in equilibrium, when the solvent molecules have an average separation distance that is equal to third root of the solvent fraction times the volume. The equilibrium remains in this situation due to collisions. Freak configurations do not occur as soon as equilibrium has been reached, because this requires a large deviation from random movement. This can only happen when work is done.
Dear Galileosays, Thanks for your kind words. When performing calculations in stat mech, we take into account ALL configurations. However, the configurations which we call 'equilibrium', that is, those configurations in which characteristic thermodynamic variables (such as the polymer-polymer distance) take their equilibrium values, represent the overwhelming majority of states. This is because that macrostate corresponds to the maximum of the entropy S, and the multiplicity, which is exp(S/kB) (kB is Boltzmann's constant) will be dominated very strongly by the configurations corresponding to the maximum of the large (extensive) quantity S. Adding the non-equilibrium configs MUST be done, but they have no effect as these states are a lot less abundant. I hope this helps. Best regards Jos
Thank you for this great video. I was wondering for the definition of Chi: when Chi is negative the interactions are favorable for the solution phase (and vice versa). But does that not mean that Jsp is big and then Jss and Jpp are small? Where does the negative sign come from?
Thanks a lot for your high-quality video! I have one question to ask for help. Because I think maybe one polymer may have different number of beads to another one. Could you explain why it is correct to assume that all the polyers have the same number (N) of beads? Thank you.
Dear Gang Huang. The fact that all polymers have the same number of beads is an assumption which facilitates the analysis. Using the techniques described in the video, you can derive the formulae for energy and entropy for a different distribution of polymer lengths but the analysis may be cumbersome.
This is such a great explanation of the Flory-Huggins theory. I am a Chemical Engineering student in my final year and have been doing Polymer Physics research with my professor for the last few years.
I remember when I first started in the research group, I looked up this video because we were working on a polymer phase separation problem and I wanted to understand what was happening. I remember not understanding anything in the video.
Now three years later, I watched your video again with a much more mature understanding of thermodynamics and stat mech and I understood everything you are saying. All in all I just want to say that I really appreciate the way you explained these difficult concepts.
Many thank for your valuable time
Thank you very much for this detailed derivation. It helps me to understand the assumption and steps which were made for this model. I like to point out that by summing over all possible solution configurations, also configurations are included which are separated and near separated configurations. This raises the question whether these configurations are allowed ?
It seems to me that some of the configurations are not equilibrium configurations and therefore not allowed to be included. That is to say, the system is in equilibrium, when the solvent molecules have an average separation distance that is equal to third root of the solvent fraction times the volume. The equilibrium remains in this situation due to collisions. Freak configurations do not occur as soon as equilibrium has been reached, because this requires a large deviation from random movement. This can only happen when work is done.
Dear Galileosays, Thanks for your kind words. When performing calculations in stat mech, we take into account ALL configurations. However, the configurations which we call 'equilibrium', that is, those configurations in which characteristic thermodynamic variables (such as the polymer-polymer distance) take their equilibrium values, represent the overwhelming majority of states. This is because that macrostate corresponds to the maximum of the entropy S, and the multiplicity, which is exp(S/kB) (kB is Boltzmann's constant) will be dominated very strongly by the configurations corresponding to the maximum of the large (extensive) quantity S. Adding the non-equilibrium configs MUST be done, but they have no effect as these states are a lot less abundant. I hope this helps. Best regards Jos
@@josthijssen6782 Thanks for this explanation. I see the microstates are all equally weighted.
Thank you for the great lecture!
Generally asked in MSc exams thanks
Thank you for this great video. I was wondering for the definition of Chi: when Chi is negative the interactions are favorable for the solution phase (and vice versa). But does that not mean that Jsp is big and then Jss and Jpp are small? Where does the negative sign come from?
Perfect
Thanks a lot for your high-quality video! I have one question to ask for help. Because I think maybe one polymer may have different number of beads to another one. Could you explain why it is correct to assume that all the polyers have the same number (N) of beads? Thank you.
Dear Gang Huang. The fact that all polymers have the same number of beads is an assumption which facilitates the analysis. Using the techniques described in the video, you can derive the formulae for energy and entropy for a different distribution of polymer lengths but the analysis may be cumbersome.
@@josthijssen6782 Thank you very much. Now I see and the constant number of beads can be seen as an ideal case.
yeh good work sir tq
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