Block Copolymers Build-up of Electron and Hole Transport Materials Marc Behl, Rudolf Zentel* Institute of Organic Chemistry, University of Mainz, Duesbergweg 10-14, D-55099 Mainz, Germany Fax: þ49 6131 39 24778; E-mail: zentel@mail.uni-mainz.de Received: March 17, 2004; Revised: May 26, 2004; Accepted: June 1, 2004; DOI: 10.1002/macp.200400110 Keywords: block copolymers; living polymerization; radical polymerization; triazines; triphenylamines Introduction In the last years much progress has been achieved in organic semiconducting materials for electronic applications like light emitting diodes (LED’s) or field-effect transis- tors (FET’s). [1–3] These materials could either be low molecular weight compounds, which have to be vacuum sublimed or polymer blends and polymers. While for the low molecular weight compounds the charge carrier mobi- lity is slightly higher than for polymers, polymers have the advantage of a much easier processing, for example by spincoating. In both cases, single molecules or polymers, these mate- rials are predominantly hole-transport (p-conductor) mate- rials, into which it is much easier to inject holes than electrons. Examples of some of the rare electron conductors are oxadiazoles, triazoles, triazines and C 60 -fullerenes. From all these materials the C 60 -fullerenes are the class with the highest charge carrier mobility. By TOF experi- ments charge carrier mobilities between of 8  10 6 m 2 V 1 s 1[4] and 5  10 5 m 2 V 1 s 1[5] could be ob- tained. However the synthesis of functionalized C 60 - fullerenes is difficult and their solubility is low. Oxadiazoles have a lower charge carrier mobility, their synthesis is easy, but their solubility is very poor. As an example a charge carrier mobility at a level about 10 3 cm 2 V 1 s 1 could be reported. [6] For triazines no charge carrier mobilities are reported, but they are known to work as electron transport materials in organic LEDs. In this case their performance is only slightly poorer than that of oxadiazoles. [7] Last but not least, the solubility of triazine compounds is satisfactory and polymers containing aromatic triazines are known to be very thermostable. Polymeric triphenyltriazines have been prepared by Thelakkat et al. as triazine ethers by conden- sation reaction. [8] These polymeric triazines fulfill the expectations as electron conductors, but because of the polycondensation their degree of polymerization is low and the degree of distribution is broad. Therefore we consider it advantageous to polymerize triazines by a radical polymerization technique. The advan- tage is a much higher molecular weight, and, if living radical polymerization [9] is possible, as proved recently [10] for one oxadiazole monomer, a considerably narrower mo- lecular weight distribution can be achieved. Summary: In this article we describe the synthesis of various monomers modified with triphenyl-1,3,5-triazine side groups as electron transport moieties. By nitroxide-mediated poly- merization with a TEMPO unimer it was possible to obtain polymers with a narrow polydispersity. Furthermore, by living radical polymerization block copolymers were obtain- ed from these monomers. Therefore, microphase separated structures are accessible which possess hole conducting moieties in one phase and electron conducting moieties in the other phase. General build-up of the copolymers consisting of hole and electron conductor. Macromol. Chem. Phys. 2004, 205, 1633–1643 DOI: 10.1002/macp.200400110 ß 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Full Paper 1633