Subject Number : S-16-NM-0007
Support Type : 機器利用
Proposal Title (English) : Stabilization of Charge Carriers in Picket-Fence Polythiophenes Using Dielectric Side Chains
Username (English) :Chunhui Zhao
Affiliation (English) : Graduate School of Pure and Applied Sciences, University of Tsukuba

1. Summary
we report a straightforward synthesis of unsheathed insulated molecular wires through Yamamoto reductive polycondensation. Despite the step-growth mechanism, block copolymers could be obtained due to the difference in the reactivity between the sheathed and unsheathed monomers.

2. Experimental
1H NMR and 13C NMR spectra were recorded on a JEOL ECS-400 spectrometer with tetramethylsilane (0 ppm for 1H) or residual CHCl3 (77 ppm for 13C) as an internal standard.
Platform staffs provided necessary instructions and supports to operate NMR.

3. Results and Discussion
Copolymerization of 3 and 4 were performed under common conditions. Namely, a solution (dimethylformamide : toluene = 1 : 8) of a mixture of 3 and 4 (9 : 1 and 8 : 2 ratios) was stirred in the presence of cyclooctadiene (COD), Ni(COD)2, and bipyridine at 90 °C for 48 hours1-2. The obtained polymers are hereafter referred to as poly-3941 and poly-3842, in which the subscripts indicate the feed ratio of the unsheathed monomer 4. Similarly, we also synthesized homopolymers, poly-3 and poly-4.

Scheme 1. Unsheathed insulated molecular wires.
1H-NMR spectra of the polymers are shown in Figure 1. Peaks that are characteristic to poly-3 (6.43 ppm) and poly-4 (7.04 ppm) are independently observed in poly-3941 and poly-3842. This result indicates that random copolymers were not formed, and that the segments of poly-3 and poly-4 are electronically independent. Compositions of poly-4 segments in poly-3941 and poly-3842 were determined to be 7.4 and 17.3%, respectively, thus were slightly smaller than the feed ratio. This result would imply that monomer 4 is less reactive than 3.

Figure 1. Partial 1H-NMR spectra of (a) poly-3, (b) poly-3941, (c) poly-3842, and (d) poly-4.

4. References
[1] K. Sugiyasu, Y. Honsho, R. M. Harrison, A. Sato, T. Yasuda, S. Seki, M. Takeuchi, J. Am. Chem. Soc. 2010, 132, 14754.
[2] U. Asawapirom, U. Scherf, Macromol. Rapid Commun. 2001, 22, 746.

5. Publication/Presentation
[1] C. Zhao, M. Takeuchi, K. Sugiyasu, Synthesis of Unsheathed Insulated Molecular Wires, Chem. Lett., 45 (2016), 1216-1218.