BF 3 $Et 2 O-mediated Friedel–Crafts C–H bond polymerization to synthesize p-conjugation-interrupted polymer semiconductors† Zheng-Dong Liu, Yong-Zheng Chang, Chang-Jin Ou, Jin-Yi Lin, Ling-Hai Xie, * Cheng-Rong Yin, Ming-Deng Yi, Yan Qian, Nai-En Shi and Wei Huang * Received 10th May 2011, Accepted 5th July 2011 DOI: 10.1039/c1py00203a C–H bond functionalization offers a chance to develop a new concept of polymerization. In this article, a family of diarylfluorene- based p-conjugation-interrupted polymers (CIPs) with nonlinear or hyperbranched frameworks have been explored by BF 3 $Et 2 O- mediated Friedel–Crafts polymerization of AB, AB 2 and AB 4 -type tertiary alcohol monomers at room temperature. Their chemical structures and optoelectronic properties have been characterized and the existence of strong intermolecular p-stacked aggregates have been observed. CIP semiconductors afford a new platform to explore novel functionality of organic devices in organic electronics or spinelectronics. Polymer semiconductors, as key active components, determine the functionality and performance in polymer devices, such as polymer light-emitting diodes (PLEDs), 1 bulk heterojunction polymer solar cells (PSCs), 2,3 polymer memory 4,5 and polymer field effect transis- tors, 6,7 affording a new chance to challenge information technology and to resolve energy and control issues. Their chemical essence is p-orbital channels, which can be created via molecular engineering or total synthesis. 8 In this framework, on one hand, it is significant to design new concept polymer semiconductors with the unique elec- tronic structure, steric hindrance, conformation and topology as well as supramolecular interaction beyond p-conjugated polymers. For example, p-conjugation-interrupted polymers (CIPs), intermediate p-systems between p-conjugated and p-stacked configurations, exhibit intrinsic nonplanar conformations, limited conjugation length and abundant conformation isomers with the potential application of wide-bandgap host electrophosphorescent materials, 8–10 electrically memorable polymers 4,5 and micro-porous materials. 11–13 On the other hand, it is more and more emergent to develop low- cost, green and eco-friendly polymerization methodologies in terms of the acceleration of commercialization. In the past several decades, transition metal-catalyzed carbon-carbon cross-coupling reaction, such as Suzuki, Negishi, Sonogashira, Stille and other reactions, afford useful tools to synthesize the polymer semiconductors. Until now, C–H bond functionalization 14,15 offers flexible and powerful synthetic protocols with the advantage being practical, atom- economical and environmentally-friendly to challenge the low-cost and environmental pollution. For example, Friedel–Crafts (F–C) reaction of arenes as conventional C–H bond functionalization has been a practical and atom-economical method since its discovery early in 1877. 16,17 F–C catalysts have allowed the initiation of cationic polymerization of vinyl monomers or the polycondensation of high- performance polyesters or polyketones via the acylation reaction of aryloyl chloride in the past century. 18–21 An alternative F–C poly- merization ultilizes the tertiary alcohol to generate carbocations. 24 However, most of them required high-temperature and harsh acid- catalyzed conditions with complicated byproducts, 22 which become a challenge when constructing polymer semiconductors for organic optoelectronics. 23 In our previous work, we have reported the developed BF 3 $Et 2 O- mediated F–C reaction to synthesise complicated 9,9-diarylfluorenes with special nonplanar conformations at room temperature 24 and F–C click post-functionalization (FCCP) of PVK to construct memorable polymers applied in nonvolatile flash memory. 4,25 We found fluorenyl tertiary alcohol with very high reactivity without steric effect, encouraging us to develop the single-monomer meth- odology (SMM) of F–C polymerization. In this communication, a series of diarylfluorene-based p-conjugation-interrupted polymers with unique conformations have been synthesized via the BF 3 $Et 2 O- mediated F–C C–H bond polymerization of AB-type, AB 2 -type or AB 4 -type monomers (Fig. 1). Preliminary photoluminescence char- acterizations exhibit anomalous photophysical properties. The synthesis of tertiary alcohol monomers and polymers are outlined in Scheme 1. We integrated thiophene and/or carbazole reactive groups into fluorene at the 2 or 7 position to construct tertiary alcohol single-monomers and to investigate the BF 3 $Et 2 O- mediated F–C C–H polymerization. Firstly, AB-type, AB 2 -type or AB 4 -type tertiary alcohol monomers, including 2-(thiophen-2-yl)- 9-(4-(octyloxy)phenyl)-fluoren-9-ol (TPFOH), 2,7-di(thiophen-2-yl)- 9-(4-(octyloxy)phenyl)-fluoren-9-ol (DTPFOH), 2-(carbazol-9-yl)-9- (4-(octyloxy)phenyl)-fluoren-9-ol (CzPFOH) and 2,7-dicarbazol-9- yl)-9-(4-(octyloxy)phenyl)-fluoren-9-ol (DCzPFOH), were designed and prepared by the Grignard reaction of ketone substituted by the electron-rich thiophene or carbazole groups with the reactivity of the Key Laboratory for Organic Electronics & Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, 9 Wenyuan Road, Nanjing, 210046, China. E-mail: iamlhxie@njupt.edu.cn; wei-huang@njupt.edu.cn; Fax: +86 25 8586 6999; Tel: +86 25 8586 6008 † Electronic supplementary information (ESI) available: Materials, experimental details and the NMR, GPC FT-IR and TGA characterization data. See DOI: 10.1039/c1py00203a This journal is ª The Royal Society of Chemistry 2011 Polym. Chem., 2011, 2, 2179–2182 | 2179 Dynamic Article Links C < Polymer Chemistry Cite this: Polym. Chem., 2011, 2, 2179 www.rsc.org/polymers COMMUNICATION Downloaded on 06 October 2011 Published on 27 July 2011 on http://pubs.rsc.org | doi:10.1039/C1PY00203A View Online