Triarylamine N-functionalized 3,6-Linked Carbazole Main Chain Polymers and Copolymers: Preparation and Physical Properties AKBAR KULASI, HUNAN YI, AHMED IRAQI Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom Received 23 June 2007; accepted 6 August 2007 DOI: 10.1002/pola.22349 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The preparation of triarylamine N-functionalized 3,6-linked carbazole homopolymers as well as alternating copolymers with 2,5-diphenyl-[1,3,4]oxadiazole and benzo[1,2,5]thiadiazole was undertaken using Suzuki cross-coupling polymeriza- tion procedures associating 3,6-bis(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-9-(bis[4- (2-butyl-octyloxy)-phenyl]-amino-phen-4-yl)-carbazole and, respectively, 3,6-dibromo-9- (bis[4-(2-butyl-octyloxy)-phenyl]-amino-phen-4-yl)-carbazole, 2,5-bis(4-bromo-phenyl)-[1, 3,4]oxadiazole, and 4,7-dibromo-benzo[1,2,5]thiadiazole. Both the carbazole homopoly- mer and alternating copolymer with 2,5-diphenyl-[1,3,4]oxadiazole were found as wide- band gap materials emitting in the blue part of the electromagnetic spectrum while the carbazole alternating copolymer with 4,7-benzo[1,2,5]thiadiazole had a narrower band gap and emitted in the orange part of the electromagnetic spectrum. The new polymers are thermally stable up to 300 8C. A discussion of the electrochemical and op- tical properties of the new polymers is presented. V V C 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5957–5967, 2007 Keywords: charge transport; conjugated polymers; light-emitting diodes INTRODUCTION Organic semiconducting materials are attracting a great deal of research interest in view of the opportunities that these materials could offer in the electronics industry. Carbazole-based materi- als constitute a unique class of organic materi- als, and polymers like poly(vinylcarbazole) have been extensively studied for their good photo- conductive properties and have found use in applications such as photocopiers and electro- photographic printing plates. More recently, these materials have found use in the area of light-emitting diodes (LEDs), both as emitting layers 1 and hole-transporting layers, 2 and also as wideband gap energy transfer materials to lower band gap emitting fluorophores. 3 However, polymers such as poly(N-vinylcarbo-zole) (PVK) do not have a conjugated backbone, which causes problems for a balanced carrier transport in LED operations. Carbazole main chain polymers have been developed as an alternative class of materi- als to PVK and two families of such materials could be distinguished: those where the carbazole repeat units are linked through the 3,6-positions 4 and those that are linked through the 2,7-posi- tions. 5 The 2,7-linked carbazole polymers are elec- trolytically less stable than their 3,6-linked ana- logues, 6 unless their 3,6-positions are protected with substituents other than hydrogen atoms. 7 Triarylamines derivatives such as 1,4-bis(1- naphthylphenylamino)-biphenyl and N,N 0 -di- phenyl-N, N 0 -bis(3-methylphenyl)-[1,1 0 -biphenyl]- 4,4 0 -diamine are widely used as hole-transport- ing materials in LED devices, 8 and are often Correspondence to: A. Iraqi (E-mail: a.iraqi@sheffield.ac. uk) Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 45, 5957–5967 (2007) V V C 2007 Wiley Periodicals, Inc. 5957