High Anionic Polymerizability of Benzofulvene: New Exo-Methylene Hydrocarbon Monomer

Abstract

The anionic polymerization of benzofulvene (BF) quantitatively proceeded with various initiators, such as secBuLi, diphenylmethyllithium, diphenylmethylpotassium, triphenylmethyllithium, and triphenylmethylpotassium, in THF at −78°C to give polymers having predicted molecular weights based on the molar ratios between BF and the initiators and narrow molecular weight distributions (MWD, M w /M n < 1.1). Although the initiation efficiencies were not quantitative, BF could also be polymerized with benzylmagnesium chloride, potassium tert-butoxide, and the anionic living poly(tert-butyl methacrylate), indicating the high anionic polymerizability. The planar conformation and the polarized electron density of BF obtained by the density functional theory (DFT) calculation supported the observed anionic polymerizability higher than that of 2-phenyl-1,3-butadiene, the acyclic analogue of BF. A series of new block copolymers, polystyrene-b-poly(BF), poly(2-vinylpyridine)-bpoly(BF), and poly(tert-butyl methacrylate)-b-poly(BF), were synthesized by the sequential anionic copolymerization of BF and the comonomers. On the other hand, no polymerization of styrene and 2-vinylpyridine took place with the living poly(BF), indicating the low nucleophilicity of the propagating indenyl anion formed from BF. BF readily underwent the free-radical polymerization with α,α′-azobis(isobutyronitrile), while the observed cationic polymerizability of BF was quite low. 1 H and 13 C NMR analyses revealed that the repeating units of poly(BF) consisted of a 1,2-addition unit and a 1,4-addition unit without a 3,4-addition unit regardless of the polymerization conditions. The exo-methylene moiety (CH 2 ) of BF always participated in the addition polymerization. The addition modes were dependent on the polymerization temperature and not on the solvent or the countercation of the anionic initiator. For instance, polymer obtained with sec-BuLi in THF at 40°C contained 72% of the 1,4-addition unit and 28% of the 1,2-addition unit. Therefore, BF acted as a polymerizable 1,3-diene possessing a fixed transoid framework.

Structural Manipulation of the Conjugated Phenyl Moiety in 3-Phenylbenzofulvene Monomers: Effects on Spontaneous Polymerization

“…However, the structure of the corresponding poly- BF derivatives was found to be rather heterogeneous. In fact, BF can behave as a 1,3-diene in the anionic polymerization and consequently the obtained polymers were demonstrated to possess, in their backbone, 1,4 and 1,2 sequences equally possible [26,27].…”

Thermoplastic Elastomers Based on Block, Graft, and Star Copolymers

“…Benzofulvene (BF), the polymer from which was irst synthesized by Ishizone, is another interesting conjugated diene monomer that undergoes living anionic polymerization in both THF and benzene [36][37][38][39]. The resulting PBF has a T g of 160°C when polymerizing in THF, and 145 o C in benzene.…”

Novel Features of 9‐Methylene‐9H‐thioxanthene (MTAE) in Living Anionic Polymerization

“…To effectively solve the above problems, different kinds of novel DPE derivatives were tried in copolymerization . Some interesting findings during copolymerization gave us unique inspiration, particularly regarding the specific designs of chemical structure . Through the introduction of three oxygen atoms as substituents, a completely new mechanism of living anionic polymerization was revealed.…”