Poly(para-phenylene vinylene) (p-PPV) derivatives – a class of conjugated polymers, suited as photoluminescence and electroluminescence materials - have been intensively studied for the past four decades.[1] Nevertheless, it is still difficult to produce blue light emitting layers due to the relatively long effective conjugation length of p-PPVs. A possible way out of this dilemma could be the use of the closely related poly(ortho-phenylene vinylene)s (o-PPVs) which are known to have significantly short conjugation lengths.[2] Although there are many approaches for the synthesis of p-PPVs, the Gilch route stands out as one of the most powerful, versatile, and simple methods.[3][4] Herein we present that the Gilch-approach is also suitable for the synthesis of o-PPV derivatives which in fact represents an alternative and new access to these promising classes of conjugated polymers. The Gilch polymerization of several monomers with different lateral substituents is described and the properties of the resulting polymers are compared with the corresponding p-PPVs. In addition to the determination of the molecular weight distributions using SEC measurements, the optical and electrochemical properties of the new o-PPV derivates were investigated using UV-Vis spectroscopy and cyclic voltammetry. The resulting emission colors and band gaps were compared with known p-PPV derivatives with similar residues, leading to valuable conclusions concerning the potential of the o-PPVs presented here as photoluminescence and electroluminescence materials.
[1] A.Greiner Polym. Adv. Technol. 1998, 9, 371-389. [2] B. Xu, J. Zhang, Y. Pan, Z. Peng Synthetic metals 1999, 107, 47-51. [3] H. G. Gilch, W.L. Wheelwright J. Polym. Sci. 1966, 4, 1337-1349. [4] T. Schwalm, J. Wiesecke, S. Immel, M. Rehahn Macromol. Rapid Commun. 2009, 30, 1295–1322.