  We present a summary of our recent publication concerning the derivation of
the extended Casimir-Polder dispersive interaction between two neutrons.
Dynamical polarizations of the neutrons, recently derived within Chiral
Effective Theory are used for the purpose. An account of the higher
frequency/energy behavior of these entities related to the opening of one-pion
production channel and the excitation of the $\Delta$ resonance are taken into
consideration in our derivation of the CP interaction. The neutron-neutron
system in free space is treated in details so are the neutron-wall and the
wall-neutron-wall systems. The case of tetraneutron (a 4 neutron system) in a
resonant state is then briefly considered. The 4n CP interaction is evaluated
to assess its potential relevance to the ongoing debate concerning the nature
of the tetraneutron.
