Anionic polymerization of isocyanates with optical functionalities

Anionic Polymerization of Chiral Isocyanate and Influence of the Initiator on Changes in the Optical Activity

“…However, the Cotton effects at 260 nm and 280 nm are due to the carbamate bonds in the side chains because the UV spectrum of the monomer (MBI) also revealed absorptions at 260 and 280 nm. This is in agreement with a previous study performed by us, [18] where polymers with azobenzene chromophores, which contained carbamate bonds, showed CD bands at 260 and 280 nm as well. Na-DPMderived polymers showed high ellipticity compared to those prepared with Na-Naph, and the results are the same as in the case of specific rotation: polymers obtained from the unidirectional initiator take on a more preferential helical conformation than those obtained from the bidirectional initiator.…”

Anionic polymerization of n‐hexyl isocyanate with monofuctional initiators. Synthesis of well‐defined diblock copolymers with styrene and isoprene

“…Immediately after the addition of HIC, the red color of the initiator solution was changed to light brown, indicating that the initiator had quantitatively reacted with the monomer. Taking into account the results reported by Lee et al24, 25 as well as the behavior obtained from the previous initiators, the polymerization was allowed to proceed for 10 min in the absence of NaBPh 4 , whereas in the presence of the additive the time was increased to 20 min. In all cases, the polymerization took place at −98 °C.…”

“…As already mentioned in the introduction, Lee's group found that bulky additives, such as 15‐crown‐5 and NaBPh 4, lead to well‐defined living PICs. In all these cases, the difunctional initiator, Na‐Naph, was used as initiator for the homopolymerization of isocyanates 23, 24. Only in one case, a monofunctional initiating system sodium diphenylmethanide was employed for the polymerization of 6‐{1‐[(S)‐(−)‐2‐methylbutyl]oxy carbonyl amino} hexyl isocyanate (yield: 72–95%; I: 1.2–1.5) 25…”

“…Recently, Lee's group reported the successful anionic living polymerization of a few isocyanates in THF, at −98 °C, with sodium naphthalenide (Na‐Naph) as initiator and crown ether 15C5 as additive 23, 24. The bulky cation (Na‐15C5) seems to prevent the backbiting zipper‐reactions of the propagating chains.…”

Synthesis of poly(2‐vinyl pyridine)‐b‐poly(n‐hexyl isocyanate) amphiphilic coil‐rod block copolymer by anionic polymerization

“…For quite some time now, we have been involved in the controlled synthesis of polyisocyanates and their copolymers. We succeeded in the living anionic polymerization of isocyanates with sodium naphthalenide (Na‐Naph) as an initiator using additives such as 15‐crown‐5 and sodium tetraphenyl borate (NaBPh 4 ) 42–46. Recently, we achieved a novel synthetic method of coil‐rod‐coil triblock copolymers of isoprene, styrene, and isocyanate via anionic polymerization 47, 48…”