Synthesis of ABA triblock copolymers via acyclic diene metathesis polymerization and living polymerization of α-amino acid-N-carboxyanhydrides

The synthesis of poly(gamma -benzyl-L-glutalnate)-b-polyoctenamer-b-poly(gamma -benzyl-L-glutamate) (13) and poly(gamma -benzyl-L-glutamate)-b-polyethylene-b-poly(gamma -benzyl-L-glutamate) (14) triblock copolymers is described, alpha,omega -Bisamino-terminated polyoctenamer (5) was used to prepare a difunctional macroinitiator (12) used for the living polymerization of gamma -benzyl-L-glutamic acid-N-carboxyanhydride (Glu-NCA) to form the triblock copolymers. 5 was synthesized by acyclic diene metathesis polymerization of 1,9-decadiene (1) in the presence of 11-phthalimido-1-undecene (2) and Grubbs' metathesis catalyst, RuCl2(=CHPh)(PCy3)(2) (3). Deprotection of the resulting phthalimide end-functionalized polymers (4) was performed, leading to difunctional 5 with number-average functionalities close to two. These methods allow the controlled preparation of polypeptide/(hydrocarbon polymer) block architectures with good control over the chain lengths of both domains and without formation of homopolypeptide contaminants.