We studied the primary photoexcitations in doubly phenyl-substituted
polyacetylenes (PDPAs) using femtosecond pump-probe spectroscopy in
the spectral range from 0.5 to 2.5 eV. We show that excitons and
neutral solitons with distinctly different absorption bands and
dynamics are photogenerated in pristine films and fullerene-doped
films within 100 fs. The obtained polarization memory decay reveals
that during relaxation excitons migrate among different polymer
chains, whereas solitons are highly localized on the chains in which
they were originally photogenerated. We also found that in
C_{60} doped PDPA the branching between neutral solitons and
intrachain emissive excitons occurs prior to the exciton
dissociation, so that the soliton band dynamics remains
unaffected. Finally, we compare the fundamental
photoexcitations in degenerate-ground state polymers to those
in nondegenerate ground state polymers.