Reasons for weakness of London dispersion force in graphite?
We need to look at the orbitals, where are the electrons localized?
because the hybridization of the carbons in grpahite are sp2 we have one free p orbital with one electron, which is denoted as the pz orbital.
The free pz electron then forms the resonance bond with the adjacent carbons. Therefore there are no non bonding valence electrons to contribute much for the London dispersion interactions.