In a polymer chain, the dihedral state can be simply distinguished as gauche and trans. What is the criterion to judge the dihedral state? Torsional angle or energy? How to judge the occurrence of gauche-trans conformation transition.
For a pure polymer, the conformation may be the most stable when the torsional angle is equal to 0 degree. However, when the second phase is added to the polymer matrix, the corresponded torsional angle of the most stable conformation may change. In other words, this criterion may be not strict for different systems.
Dear Yancong,
My dim memory of polymer chemistry is that in Rotational Isomeric State Models (RISM) that one needs both the dihedral angles and the associated energies for a state in which bond (i) has a specified angular orientation relative to the immediately prior bond (i-1) which likewise has a specified orientation.
Old RISM calculations set the trans configuration as zero energy and then parametized the assignment for the gauche, I believe. These days I think simulations such as modern density functional theory (DFT) are sometimes used to set those energy differentials between the dihedral configurations of the neighboring groups.
Best regards,
Mike
I agree. Both torsional angles and energy values should be used
Thank you for your answers!
I wonder the detail of the criterion. Take the torsional angle as the criterion for example. I can calculate all the torsional angles based on the result using molecular dynamics simulation. If the torsional angle of trans state equal to about 0 degree, what is the region of angle? e.g. for the region (-x, x), how to get the value of x. Assume that the trans, gauche state and the energy barrier are equal to about 0, 120, 60, respectively. If the torsional angle change from 50 to 70 degree, is this a trans-to-gauche transition?
Thank you very much!
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