Our approach consists of improving the molecular architecture of π-electron delocalization and orientations of the polymeric backbone of materials for cubic nonlinear optics. First, the syntheses of new polymers such as substituted polyacetylenes or polyphenyleneynylenes were done, in which the stiff conjugated chain and the flexible side-chains are well adapted to the orientation of the backbone. They have been studied for their third order susceptibility and their ability to give processable optical films. We have found liquid crystal properties with the rigid rod derivative of the poly(ethynylarylene). Unlike previous poly(ethynylarylene), we obtained a high molecular weight: , which allows films of good optical and mechanical properties. Second, in order to increase the third order response, we focused our attention on the orientational order of polydiacetylenes, which we obtained by epitaxial growth of the monomer on a single crystal substrate. From the proposed epitaxial model a possible extension of highly oriented thin films can be applied to a large class of materials.