Chemical pretreatment of a polyoriented platinum single crystal has been performed with alkylthiols CH3(CH2)(n)SH, n = 0 to 2, 6, 9, and aromatic thiols such as Phi-(CH2)(m)-SH (m = 0 to 3), thiocresol (ortho, meta and para), dimethylthiophenol (2,5-; 3,4-; 3,5-; 3,6-), by dipping in thiol solution. Polybithiophene films are then electrochemically grown on such pretreated platinum. Using electrochemistry and W-Vis spectroscopy, and by comparison with polymer grafted onto unpretreated platinum, the effect of pretreatment on film properties is analyzed as a function of molecular structure, chain length of thiols, initially adsorbed oxygen, medium and polybithiophene film thicknesses. The influence of surface pretreatment on the nucleation and film growth, and the requirement of an aromatic function for grafting and a good adhesion of the polymer are demonstrated.