  We investigate the stellar populations of galaxies in clusters at different
dynamical stages, aiming to identify possible effects of the relaxation state
of the cluster or subcluster on the star formation histories of its galaxies.
We have developed and applied a code for kinematic substructure detection to a
sample of 412 galaxy clusters drawn from the \citet[]{tempel2012} catalogue,
finding a frequency of substructures of 45\%. We have extracted mean stellar
ages with the {\sc{starlight}} spectral synthesis code applied to SDSS-III
spectra of the sample galaxies. We found lower mean stellar ages in unrelaxed
clusters relative to relaxed clusters. For unrelaxed clusters, we separated
primary and secondary subhalos and found that, while relaxed clusters and
primaries present similar masses and age distributions, secondaries present
younger stellar populations, mainly due to low-mass galaxies ($\log
M_\star/M_\odot \lesssim 11$\,dex). An age-clustercentric radius relation is
seen for all subhalos irrespective of the presence of substructures. We also
observe relations between the mean stellar age and mass of relaxed and
unrelaxed clusters, massive systems presenting higher mean ages. The locus of
these relations is distinct between relaxed and unrelaxed clusters, but become
indistinguishable when separating primaries and secondaries. Our results
suggest that differences between relaxed and unrelaxed clusters are mainly
driven by low-mass systems in the clusters outskirts, and that, while
pre-processing can be seen in the subcomponents of dynamically young clusters,
some evolution in the stellar populations must occur during the clusters
relaxation.
