Homo and Block Copolymers of Poly(β-benzyl-L-aspartate)s and Poly(γ-benzyl-L-glutamate)s of Different Architectures

Homopolypeptides of linear and star‐like architectures were prepared by polymerizing benzylic‐protected L‐glutamic acid and L‐aspartic acid N‐carboxyanhydrides (Glu NCA, Asp NCA) in DMF. The polymerization rate of the Glu NCA is faster than that of Asp NCA. Using a simple monoamino initiator, its hydrochloride, di‐, tri‐, and tetraamino functional initiators, homopolypeptides with well‐defined structures and molar masses were obtained. The molar‐mass averages of the poly(γ‐benzyl‐L‐glutamate)s lie very close to calculated values, according to the initial [M]:[I] ratios, while those of the linear poly(β‐benzyl‐L‐aspartate)s were lower than the predicted ones. PBAs had somewhat broader molar‐mass distributions than PBGs. The polymerizations of benzylic‐protected L‐aspartic acid N‐carboxyanhydrides and L‐glutamic acid N‐carboxyanhydrides using mono‐ and polyamino functional initiators are described. The rate constants for the hexylamine‐initiated polymerizations are evaluated using 1H NMR and possible reasons for the differences in their reactivities are discussed.