Novel amphiphilic multistimuli-responsive diblock copolymers and comparison between their self-assembly and controlled release behavior

Here, we reported three novel multistimuli-responsive copolymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. They have the same hydrophilic block and different hydrophobic block which contain azobenzene or ferrocene or both, thus leads to different stimuli-response. Poly[2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl methacrylate]28-b-P[(E)-2-((2-(methacryloyloxy)ethyl)(methyl)amino)ethyl 4-(phenyldiazenyl) benzoate]38 (PMEO4MA28-b-P(Azo-N-MA)38) was temperature/pH/light-responsive with a lower critical solution temperature (LCST)-type cloud point (CP) of 68 °C and a critical pH of 3.5 in water, upper critical solution temperature (UCST) was shown in alcohols, and its light-response was confirmed by UV/vis absorption spectra by alternating UV/blue light radiation; Poly[2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl methacrylate]28-b-P[2-((2-ferrocenyl ethyl ester) (methyl)amino)ethyl methacrylate]40 (PMEO4MA28-b-P(Fc-N-MA)40) was temperature/pH/redox-responsive and has a critical pH of 2.5 in water and an UCST-type CP in nPrOH, its redox-response was confirmed by UV/vis absorption spectra by addition of FeCl3 and VC. PMEO4MA28-b-[P(Azo-N-MA)–co-P(Fc-N-MA)]40 was temperature/pH/light/redox-responsive and has a critical pH of 3.0 in water and an UCST-type CP in nPrOH. The three copolymers can self-assemble into spherical, vesicular and spherical micelles in water, respectively. Evolution process of morphologies of micelles under different stimuli was then studied. Finally, by wrapping of Nile Red (NR), their controlled release behavior was compared and discussed. The three copolymers have simple synthesis steps, diverse and sensitive response, and have good application prospects in the field of self-assembly and drug release.