  Electronic excitations in dilute solutions of poly para phenylene ethynylene
(poly-PPE) are studied using a QM/MM approach combining many-body Green's
functions theory within the $GW$ approximation and the Bethe-Salpeter equation
with polarizable force field models. Oligomers up to a length of 7.5\,nm (10
repeat units) functionalized with nonyl side chains are solvated in toluene and
water, respectively. After equilibration using atomistic molecular dynamics
(MD), the system is partitioned into a quantum region (backbone) embedded into
a classical (side chains and solvent) environment. Optical absorption
properties are calculated solving the coupled QM/MM system self-consistently
and special attention is paid to the effects of solvents. The model allows to
differentiate the influence of oligomer conformation induced by the solvation
from electronic effects related to local electric fields and polarization. It
is found that the electronic environment contributions are negligible compared
to the conformational dynamics of the conjugated PPE. An analysis of the
electron-hole wave function reveals a sensitivity of energy and localization
characteristics of the excited states to bends in the global conformation of
the oligomer rather than to the relative of phenyl rings along the backbone.
