Synthesis of star poly(1,3‐cyclohexadiene): Grafting reaction of poly(1,3‐cyclohexadienyl)lithium onto C₆₀

Abstract

The grafting reaction of poly(1,3-cyclohexadienyl)lithium onto fullerene-C 60 (C 60) was strongly affected by the nucleophilicity of poly(1,3-cyclohexadiene) (PCHD) carbanions and the polymer chain microstructure, and progressed via stepby-step reactions. A star-shaped PCHD, having a maximum of four arms, was obtained from poly(1,3-cyclohexadienyl)lithium composed of all 1,4-cyclohexadiene (1,4-CHD) units. The rate of the grafting reaction was accelerated by the addition of amine. The grafting density of PCHD arms onto C 60 decreased with an increase in the molar ratio of 1,2-cyclohexadiene (1,2-CHD) units. The electron-transfer reaction from PCHD carbanions to C 60 did not occur in either a nonpolar solvent or a polar solvent. V

Degradation of the covalent carbon–carbon bond between fullerene‐C60 and poly(1,3‐cyclohexadiene)

“…They hypothesized that the elimination of the PIp‐PSt arm from a C 60 was because of the cleavage of the C 60 ‐PIp bond via a 1,5‐sigmatropic H‐shift 2. With respect to the C 60 ‐PCHD bond, François et al and we noticed that the elimination of both PCHD‐PSt3 and PCHD4 arms from C 60 ‐PCHD‐PSt and C 60 ‐PCHD was observed in the presence of 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ, a typical strong dehydrogenation reagent). However, the mechanism of this degradation reaction has been unclear until now.…”

“…As explained in a previous paper,4 PCHD produces almost no UV absorption in the region greater than 225 nm, and has good solubility in THF. In contrast, C 60 has strong absorption peaks near 260 and 330 nm, and is insoluble in THF.…”

“…In contrast, C 60 has strong absorption peaks near 260 and 330 nm, and is insoluble in THF. Therefore, C 60 ‐PCHD obtained by the grafting of PCHDLi onto C 60 shows strong absorption in the region greater than 225 nm, and is readily soluble in THF 4. Using this characteristic of C 60 ‐PCHD, the grafting density (i.e., approximation of the number of PCHD arm molecules on C 60 ) of PCHD arms onto C 60 can be estimated by the following procedure.…”

“…Recently, we reported that a well‐defined C 60 ‐PCHD, having a maximum of four arms, was obtained by the grafting reaction of poly(1,3‐cyclohexadienyl)lithium (PCHDLi) onto C 60 (Scheme ) 4, 11. The thermal stability of the C 60 ‐PCHD bond was also revealed (the C 60 ‐PCHD bond was very stable at room temperature.…”

“…The synthesis of fullerene‐C 60 (C 60 ) end‐capped polymers (C 60 ‐polymers) is one of the most interesting subjects in basic polymer research and is a practical method to obtain new functional materials for a wide range of applications. For example, C 60 ‐polystyrene (C 60 ‐PSt), 1 C 60 ‐polyisoprene (C 60 ‐PIp),1 C 60 ‐PIp‐PSt block copolymer (C 60 ‐PIp‐PSt),2 C 60 ‐PSt‐poly(1,3‐cyclohexadiene) (PCHD) block copolymer (C 60 ‐PSt‐PCHD),3 C 60 ‐PCHD,4 C 60 ‐poly( N ‐vinylcarbazole) (C 60 ‐PNVC),5 and C 60 ‐poly(4‐diphenylaminostyrene) (C 60 ‐PDAS)6 were synthesized by the grafting reaction of polymer carbanions onto C 60 . Among the innumerable combinations of C 60 and polymers, C 60 ‐poly( para ‐phenylene) (C 60 ‐PPP) has been recognized as one of the most attractive structures, because excellent optical, electrical, and opto‐electrical properties are expected from this polymer.…”