Two polythiophene based polymers,poly[(3-[2-[4-(2-ethyl-hexyloxy)-phenyl]-vinyl]-thiophene)-co-thiophene] (PT1)and poly(3-[2-[4-(2-ethyl-hexyloxy)-phenyl]-vinyl]-thiophene) (PT2),are synthesized and investigated by static,picosecond fluorescence spectroscopies and the femtosecond up-conversion technique in solution.Compared with pristine poly(3-hexylthiophene) (P3HT),PT1 and PT2,in which the main chains are decorated with phenyl vinylene present a camel back structure in the absorption spectra.Phenyl vinylene side chains induce a new process of charge transfer,chain twisting motion and defect-induced fluorescence quenching at time scales of 1 ps,10ps and 150 ps,respectively.Polythiophene is a kind of promising low-cost and flexible material for electronic devices.[1-7] Its performance is strongly affected by its morphology and corresponding photophysical behavior.The formation of intrachain excitons is at ～100fs.Their decays are from several hundreds of femtosecond to subnanosecond (～600ps).[4,8-10] Downhill energy transfer is the first decay process at ～1 ps or less,while the longest decay from thermalized excitons happens at several hundreds of picosecond.[8] The conformational relaxation related to energy transfer along the polymer chains occurring at tens of picosecond has been determined.[11-13] Introducing side chains on polythiophene backbone makes the polymer soluble and processable.Moreover,side chains can modify the electronic properties of the polymer such as bandgap or exciton transfer process.