[Enthalpy]

The m- and p- diacids have different melting points. Separate them by solidification of the vapour at low pressure? Though less easy in a lab, it would be an industrial process.

From what I read on Wiki, the diacids are made by catalytic oxidation of m- and p- xylene with oxygen. That looks affordable.

If you like polymers...
https://www.chemicalforums.com/index.php?&topic=62053.0
I ignore what I obtained. A C₂ polyketone might be a nice ferroelectric polymer. Or a C₄ one, from CO and cyclopropane?