Impact of Tuning the Hydrophobicity in ABA‐Type Amphiphilic Polythiourethane on the Dye Loading and Stability of Formed Polymersomes Using Pendant Aromatic Groups

Abstract Polymersomes are polymeric vesicles composed of amphiphilic block copolymers with a hydrophilic inner lumen and a hydrophobic membrane, capable of encapsulating both hydrophilic payloads, and hydrophobic payloads. The one‐pot synthesis and self‐assembly of polyethylene‐glycol‐based amphiphilic polythiourethanes consisting of a pendant methyl or aromatic ester are reported here. During the ring opening of cyclodithiocarbonate using ethylene diamine or hexyl diamine, generated thiols are utilized to modify the backbone with methyl, benzyl, and diphenyl esters. The aromatic pendant containing P3 and P4 has higher hydrophobic dye loading than the other methyl ester containing polymers P1 and P2. All the polymers have hydrodynamic diameters in the range of 40–98 nm. Atomic force microscopy (AFM) results show that all the polymers are able to form spherical aggregates with diameters of 38.1 ± 7.7 and 85.1 ± 27.4 nm. Among them, aromatic side‐chain‐containing polymers have 42% and 57% calcein encapsulation efficiency, whereas methyl‐ester‐containing polymers have 70% and 60% efficiency. The polymers with longer spacers (P2–P4) and aromatic groups (P3 and P4) have shown better stability and slow dye exchange over 48 h compared to the polymer with an aliphatic side chain and a shorter spacer probed by fluorescence resonance energy transfer (FRET) study.