Synthesis of Amphiphilic Miktoarm Star Copolymers of Poly(n-hexyl isocyanate) and Poly(ethylene glycol) through Reaction with the Active Methylene Group

Coupling of the living poly( n -hexyl isocyanate) (PHIC) with malonyl chloride in the presence of pyridine resulted in a well-defined polymer PHIC-COCH 2 CO-PHIC in ∼95% yields. The active methylene group in the center of the polymer is a site for the introduction of suitable functionalities so as to impart additional attributes to the polymer. Poly(ethylene glycol) was anchored to the polymer center using monomethacrylate poly(ethylene glycol) (PEG1) by Michael addition reaction leading to the amphiphilc copolymer (PHIC) 2 -PEG1. Two molecules of PHIC-COCH 2 CO-PHIC were linked with a dimethacrylate poly(ethylene glycol) (PEG2) leading to (PHIC) 2 -PEG2-(PHIC) 2 . These miktoarm star copolymers of A 2 B and A 2 BA 2 architecture, where A is the hydrophobic PHIC and B is the hydrophilic and biocompatible PEG, were isolated in ∼90% yields with controlled molecular weight and narrow molecular weight distribution (1.08−1.14). The amphiphilic A 2 B-type copolymers formed solid micelles in CHCl 3 and vesicles in THF:C 2 H 5 OH (1:9 v/v) mixed solvent.