Self-Assembly of Amphiphilic Copolymers: Exploring Block Copolymer Structures
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Self-assembly of amphiphilic copolymers in selective solvents is a broad research field due to the significant potential applications of the resulting nanostructures such as drug delivery. Previous studies have shown the effect of several factors on self-assembly behavior. For example, diverse block length ratios between hydrophilic and hydrophobic blocks produce structures ranging from spherical micelles to polymer vesicle. In addition, segregation of hydrophilic blocks by length stabilizes curvature of vesicles. However, due to the polydispersity of block copolymers, it is unclear whether the difference in hydrophilic block lengths is actually responsible for the stable curvature of the vesicles. Herein, we self-assembled amphiphilic block copolymers composed of discrete number of orthogonally protected monomers based on malic acid with butyl and benzyl side-chain substituents. The monomers were derived from L-malic acid by selective acetonide protecting of the α-hydroxy acid, achieving respective benzylation and butylation of the remaining β-carboxylic acid, and then deprotecting of the acetonide group. For iterative exponential growth, the residual hydroxyl and carboxyl groups were protected by tert-butyldimethylsilyl and allyl groups, respectively. Hydrogenolysis of the benzyl group on side chain was finally performed to expose carboxylic acid for hydrophilicity.