Synthesis of lysine-based amphiphilic random copolymers capable of self-assembly in water

Abstract

A series of copolymers featuring polyamide-6 skeleton were synthesized through the ring-opening copolymerization of seven membered cyclic lactam monomers derived from lysine with varying degrees of hydrophilicity. Dimethyl protected cyclic lysine (DMCL) serves as a certainly hydrophilic comonomer, while the hydrophobic comonomer bears longer substitutive alkyl groups on the side nitrogen atom, such as dibutyl protected cyclic lysine (DBCL). Both calculations and experimental results indicate the resulted copolymers possess random structures. Nevertheless, amphiphilic copolymers can be achieved by reasonably adjusting the length of the alkyl chain in the hydrophobic monomer and flexibly varying the ratio of hydrophilic and hydrophobic units. Notably, poly(DMCL-co-DBCL)73, which has a hydrophilic to hydrophobic ratio of 7 to 3, is capable of self-assembling into well-defined micelles in water and showed excellent potential for drug delivery applications.