Molecular assembly of alkyl chain-grafted poly(l-lysine) tuned by backbone chain length and grafted alkyl chain

Abstract

The preparation of alkyl chain-grafted poly(L-lysine) (PLL) vesicles with tunable molecular assembly by varying the polypeptide chain length and grafted alkyl chain under different solution conditions was investigated. These amphiphilic copolypeptides self-assembled to form vesicular nanostructures with average sizes between 60 and 400 nm under acidic and neutral conditions. The molecular packing of alkyl chain-grafted PLL was determined by the degree of alkyl chain substitution (DS) and grafted alkyl chain length. Upon increasing the DS and/or alkyl chain length, the chain conformation changed from random coils to a helical conformation, which accompanied the protonation/deprotonation of the amino group, leading to changes in the amphiphilic nature of the copolypeptides and subsequently the vesicular size. It was found that the vesicular size and chain conformation adopted by PLL were also influenced by the backbone chain length, depending on the DS and alkyl chain length. With the versatility of the synthesis strategy, it is expected that additional functionality can be incorporated onto these copolypeptides for specific purposes.