Synthesis and Self-assembly of a Simple CO₂-responsive Diblock Polymer

Methoxypolyethylene glycol 1900 and α-bromoisobutanoyl bromide were utilized for alcoholysis reaction to obtain a macromolecular initiator. Then, a simple amphiphilic diblockpolymer (mPEG-PDMAEMA) based on the initiator and dimethylaminoethyl methacrylate was synthesized through the atomic transfer radical polymerization (ATRP) method. The structures of the initiator and diblock polymer were accurately characterized using infrared spectrum and proton nuclear magnetic resonance spectroscopy (¹H NMR). Cryo-transmission electron microscopy revealed the self-assembly of mPEG-PDMAEMA into vesicle-like structures in water. Upon injection of CO₂ into the solution, the tertiary amine structure within PDMAEMA underwent protonation, resulting in the mPEG-PDMAEMA adopting a hydrophilic structure. Consequently, the vesicles dissociated and dispersed, forming a network-like structure in water. The protonation phenomenon was confirmed by ¹H NMR, as evidenced by the shifting of alkyl hydrogen atoms near nitrogen atoms toward downfield positions.