Combining neutron diffraction with polarization analysis on isotopically labeled samples and fully atomistic molecular dynamics simulations, we have unravelled the structural features of the poly(alkylene oxide)s (PAOs) series. The experimental results show clear signatures of nanosegregation of main chains and side groups leading to the presence of alkyl nanodomains, as previously reported for other comb-like polymers like poly(n-alkyl methacrylates) (PnMAs). Comparison with polyethylene (PE) data shows that the atomic arrangements of side groups within the nanodomains in PAOs are more similar to bulk PE than those in PnMAs. After validating the simulations by direct comparison with the diffraction results on deuterated and protonated samples, we have exploited them to unveil the origin of the structure factor peaks and predict the outcome of potential neutron diffraction experiments on partially labeled samples. The simulated structures undoubtedly confirm the nanosegregation scenario in PAOs.