The invention relates to an actuator for converting between mechanical and electrical energy comprising—at least two electrodes; and—an electroactive polymer, comprising aromatic moieties in the chain and flexible moieties in the chain, the polymer further comprising side groups bound to the chain, which side groups are selected from the group consisting of polar side groups and side groups comprising an aromatic moiety. The invention further relates to a novel electroactive polymer comprising polar side groups bound to the chain.