Fundamental Kinetics of Living Anionic Polymerization of Isocyanates Emerging by the Sodium Diphenylmethane-Mediated Initiation

Anionic polymerization of n-hexyl isocyanate (HIC) in THF at −98 °C under 10–6 Torr for the kinetic study was performed by the initiation of sodium diphenylmethane (NaDPM) in either the absence or presence of sodium tetraphenylborate (NaBPh4; [NaBPh4]0/[NaDPM]0 = 0 or 5). The common-ion effect of NaBPh4 to suppress the formation of unstable free amidate anions led to termination-free propagation by amidate ion pairs. In [HIC]0/[NaDPM]0 = 50.8/101/201, the initiation of NaDPM early reached ∼100% efficiencies during propagation, which led to the yield of poly­(n-hexyl isocyanate)­s (PHICs) with predictable molecular weights (M n,theo = 6.50/12.7/24.7 kDa; M n = 6.50/12.7/26.1 kDa) and low dispersities (Đ = 1.06/1.07/1.15). Within the conditions, the rate of propagation accorded with a first-order dependence on [NaDPM]0, indicating that the propagating amidate ion pairs are intrinsically unimeric (nonassociated). Kinetics of anionic copolymerization of HIC and allyl isocyanate (AIC) exhibited a monomer distribution toward a tapered block sequence.