New 3-alkylthiophene copolymers functionalized with a NLO chromophore C. Della-Casa * , A. Fraleoni, P. Costa-Bizzarri, M. Lanzi Dipartimento di Chimica Industriale e dei Materiali, Universita Á di Bologna, viale Risorgimento 4, I-40136 Bologna, Italy Received 2 February 2001; received in revised form 21 March 2001; accepted 8 May 2001 Abstract New soluble functionalized 3-alkylthiophene copolymers have been prepared by a chemical oxidative method with FeCl 3 . The starting comonomers were 3-hexylthiophene and 3-alkylthiophenes with an azobenzene chromophore grafted to the side chains. Characterizations of the copolymers have been reported. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Functionalized polythiophenes; Azobenzene chromophore; Solvatochromism 1. Introduction In the class of intrinsically conducting polymers, that is polymers with p-conjugated backbones, polythiophenes are very interesting because of their good thermal and chemical stability and relative ease of functionalization which poten- tially permit a ®ne tuning of their physical and electronic properties. Moreover, polyconjugated chains exhibit third- order non-linear optical NLO) behaviour [1]. In the light of these characteristics the functionalization of polythiophenes withNLOchromophoresmaybeofinterestintheattemptto combine different interesting properties in one material and to achieve multifunctional polymers. On the other hand, over the last few years, organic materials exhibiting NLO properties have been the subject of intense investigations for their possible technological applications such as data storage and data transmission. In particular, polymers containing NLO chromophores che- mically attached to the backbone seem to be very promising for these purposes [2,3]. Inviewoftheabove,wefocusedinthepresentpaperon3- alkyl substituted polythiophenes for their processibility, grafting a chromophoric unit possessing a donor and an acceptor group to the end of the 3-alkyl chain of the thiophene ring so as to obtain chromophoric monomers. To the best of our knowledge, there is little literature dealing with alkylthiophene monomers substituted with push±pull p-conjugated units potentially available for NLO applica- tions [4,5]. 2. Experimental 2.1. Synthesis of monomers Monomers 4 and 6 were obtained with >80% yields through the reaction of 4-hydroxy-4 0 -nitroazobenzene 3) with 2-3-thienyl)ethyl-p-toluenesulfonate 2) and 3-6-bro- mohexyl) thiophene 5), respectively Scheme 1). Com- pounds 3 and 5 were prepared according to procedures described in the literature [6,7] while compound 2, which was chosen for being more reactive than the corresponding 2-3-thienyl)ethyl bromide, was synthesized from commer- cial 2-3-thienyl)ethanol 1) with tosyl chloride by the general procedure commonly used for the preparation of tosyl derivatives. 4: mp 143±1448C; d H 200 MHz, CDCl 3 ) 8.36 d, 2H), 7.98 dd, 4H), 7.37±6.98 m, 5H), 4.30 t, 2H), 3.21 t, 2H) ppm; d C 300 MHz, CDCl 3 ) 162.49, 156.02, 148.25, 146.96, 138.02, 128.51, 128.37, 125.72, 125.62, 124.95, 124.70, 123.11, 121.78, 115.56, 114.98, 68.46 CH 2 O), 30.12 Th-CH 2 ) ppm; m/z relative intensity) 353 16, M ), 111 100, C 6 H 7 S ). 6: mp 122±1238C; d H 200 MHz, CDCl 3 ) 8.37 d, 2H), 7.97dd,4H),7.34m,1H),7.07±6.90m,4H),4.06t,2H), 2.66 t, 2H), 1.96±1.31 bm, 8H) ppm; d C 300 MHz, CDCl 3 ) 162.88, 156.03, 148.17, 146.77, 142.91, 128.21, Synthetic Metals 124 2001) 467±470 * Corresponding author. Tel.: 39-51-2093669; fax: 39-51-2093654. E-mail address: casa@ms.fci.unibo.it C. Della-Casa). 0379-6779/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0379-677901)00401-5