Formation of Well‐Defined Block Copolymer Vesicles with a Narrow Distribution Induced by Targeted Hydrolysis of Silyl Ether Bond in a PEG‐PDMS‐PEG Triblock Copolymer

ABSTRACT Base‐catalyzed ring opening polymerization (ROP) of cyclosiloxane D3 was conducted using various alcohols as initiators to produce end‐group functional poly(dimethylsiloxane)(PDMS). To demonstrate the concept for vesicle formation, a poly(ethylene glycol)‐b‐poly(dimethyl siloxane)‐b‐poly(ethylene glycol) (PEG‐PDMS‐PEG) triblock copolymer, where one PEG block was attached through a stable carbosilane bond while the other PEG was coupled through a hydrolytically labile silyl ether linkage was prepared. Non‐catalyzed hydrolysis of this copolymer in aqueous suspension led to a slow transformation of the triblock into the corresponding diblock copolymer and, conversely, to the transformation of the initially formed large aggregates into well‐defined vesicles with a diameter of less than 100 nm over one week. In contrast, a control triblock copolymer with the same composition but without the silyl ether bond did not change morphology.