A new series of biphenylene ethynylene co-polymers, poly(2,5-dialkoxy-4-phenyleneethynylene-4,4-biphenyleneethynylene)s of the general formula [-C≡C-4-C 6 H 4-C 6 H 4-4-C≡C-C 6 H 2 (2,5-OR) 2-] n (R = C 4 H 9 P1,C 8 H 17 P2) has been synthesized using a palladium/copper catalyzed coupling reaction between HC≡C-4-C 6 H 4-C 6 H 4-4-C≡C-H and IC 6 H 2 (2,5-OR) 2 I. The new co-polymer [-C≡C-C 6 H 2 (2,5-OC 8 H 17) 2-C≡C-C 6 H 2 (2,5-OC 4 H 9) 2-] n P5 has also been formed where different alkoxy substituents are present on alternate arene rings in the same polymer backbone. All the polymers were characterized by IR, 1 H and 13 C NMR spectroscopy and by GPC. The model compounds C 6 H 5-4-C 6 H 4-C≡C-C 6 H 2 (2,5-OR) 2-4-C 6 H 4-C 6 H 5 (R = C 4 H 9 M1,C 8 H 17 M2) have also been prepared by the reaction between C 6 H 5-4-C 6 H 4-C≡CH and IC 6 H 2 (2,5-OR) 2 I. Single crystal X-ray structures of M1, M2 and Me 3 Si-C≡C-4-C 6 H 4-C 6 H 4-4-C≡C-SiMe 3 were determined with a view to obtain a better understanding of the molecular and intermolecular interactions in the solid state which has been used to explain the optical properties of the polymers derived from them. The absorption and photoluminescence spectra of the polymers, P1, P2 and P5 showed that the lowest energy band is blue shifted due to the introduction of biphenylene fragments into the alkoxy substituted poly(ethynylenephenylene)s.