Hi, All!

Recently, I am trying to carry out DPD simulation for polymer blend system.

However, I have met a problem to caculate chi parameter using molar volume.

I am interested in Polyimides(PIs) for this simulation.

Since PIs have rigid monomer structures having cyclic rings, their molar volumes are much higher than general aliphatic polymers shown in MS modeling DPD Tutorial.

For example, my structure has ca. 290 of molar volume caculated by Synthia, but PS or PP in the tutorial have molar volumes less than 100.

Considering those structures, these values are reasonable.

But, my real problem is the next step.

Since Chi parameter is proposional to Vref(Solubility1-Solubility2)^2, when I caculate the Chi parameters of PI-other polymer blend, its value becomes too high, depite small difference in their solubility parameters.

Finally, every system is completely separated even in the case that experimentally both polymers can be mixed well.

In this case that molar volume is very high over 200, shoul I use the high value as calculated or is there any other tip?

In addition, when I calculated Chi parameter, which should I use the averaged molar volume or the higher one between two different values (ex: PP=40, PI=200) ?

Thanks in advance.

Best regards