Anionic Polymerization of Reactive 3-Chloropropyl Isocyanate

Summary For the synthesis of a new functional polyisocyanate, the anionic polymerization of 3-chloropropyl isocyanate (3CPIC) was carried out using several initiator systems in THF at −98 °C. When a sodium benzanilide (Na-BA) cluster was used as an aggregated initiator, the initiation efficiency and polymer yield were low due to too fast propagation and cyclic trimerization compared to the initiation. A more reactive oligo(n-hexyl isocyanate)sodium/Na-BA cluster improved the initiation efficiency and polymer yield, but trimerization still occurred. A nearly quantitative yield was achieved by oligo(2-vinylpyridinyl)potassium in the presence of a large excess of sodium tetraphenylborate (NaBPh4). In this case, highly dissociating and bulky NaBPh4 reduced the propagation rate and protected the propagating chain end from trimerization through steric hindrance. This advantage of NaBPh4 was cancelled by the decreased initiation efficiency. All polymerization trials resulted in uncontrolled molecular weight properties. The chloropropyl side groups of the obtained P3CPIC reacted with polystyryllithium to generate poly(3-chloropropyl isocyanate)-graft-polystyrene (P3CPIC-g-PS) through the grafting-onto method.