Synthesis of 3-and 4-arm star-block copolypeptides using multifunctional amino initiators and high vacuum techniques

Three- and four-arm star-block copolypepticles, (BL-b-G)(3) and (G-b-BL)(4) of poly(F,-butyloxycarbonyl-L-lysine) (BL) and poly(gamma-benzyl-L-glutamate) (G), were synthesized under high vacuum conditions, using three different multifunctional aminoinitiators for the ring opening polymerization of the corresponding alpha-aminoacid N-carboxyanhydrides. When the initiator contained only primary amine groups 12(aminomethyl)-2-methyl-1,3-propanediamine, AMPDA}, well-defined star-block copolypeptides with monomodal molecular weight distribution were produced. However, if the multifunctional initiator contained both primary and tertiary amine groups 1polypropylenimine tetraamine dendrimer, generation 1.0 (DAB); amidoethylethanolamine dendrimer, 1,4-diaminobutane core, generation 0.0 (PAMAM)1, bimodal high polydispersed copolypepticles were formed. The different behaviors are due to the participation of both the primary and tertiary amino groups, each following different polymerization kinetics.