We used a TD-DFT approach relying on range-separated hybrids to evaluate the photon induced charge-transfer of substituted polyene oligomers of increasingly long chains. Several exchange correlation functionals have been considered. Push, pull and push pull systems containing up to 20 unit cells have been compared. A cooperative, but non additive, impact of the donor and acceptor groups is found. In long oligomers, the changes in the electronic density are mainly located on the central segment and not on the terminal electroactive groups, but the charge-transfer distance remains large, which contrasts with most push pull compounds. (C) 2013 Elsevier B.V. All rights reserved.