  We present a determination of optical potentials using the double-folding
method based on chiral effective field theory nucleon-nucleon interactions at
next-to-next-to-leading order combined with dispersion relations to constrain
the imaginary part. This approach is benchmarked on $^{16}$O--$^{16}$O
collisions, and extended to the $^{12}$C--$^{12}$C and $^{12}$C--$^{16}$O
cases. Predictions derived from these potentials are compared to data for
elastic scattering at energies up to 1000 MeV, as well as for fusion at low
energy. Without adjusting parameters, excellent agreement with experiment is
found. In addition, we study the sensitivity of the corresponding cross
sections to the nucleon-nucleon interactions and nuclear densities used.
