Living Anionic Polymerization of Isocyanate Containing a Reactive Carbamate Group

Anionic polymerization of n-alkoxycarbonylaminohexyl isocyanates was carried out using a sodium benzanilide (Na-BA)as an initiator without additives in tetrahydrofuran (THF)at -98 degrees C under high vacuum (10(-6) Torr). The polymerization of methoxycarbonylaminohexyl isocyanate (MAHI) resulted in an insoluble material. However, the polymerization of n-propyloxycarbonylaminohexyl isocyanate (PAHI) with propyl side chain was moderately controlled and gave high yields (similar to 98%) of the polymers with polydispersity index (PDI 1.18-1.22). The results of the polymerization were improved significantly when n-pentanoxycarbonylaminohexyl isocyanate (PEAHI) with pentyl side chain was used. Poly(n-pentanoxycarbonylaminohexyl isocyanate) (PPEAHI) was isolated in similar to 99% yields, controlled molecular weight, and a narrow PDI (1.08-1.14). The living nature of PPEAHI was indicated from the linear plot of the molar ratio of the monomer to the initiator versus the number-average molecular weight (M-n) in addition to the successful block copolymerization of PEAHI with another isocyanate monomer, n-hexyl isocyanate (HIC). Furthermore, the hydrogen bonding between the active hydrogen of the carbamate group of the PPEAHI and the nitrogen atom of the poly(2-vinylpyridine) formed a vesicle-like morphology in methanol.