Advances in PEG-based ABC terpolymers and their applications

Abstract

ABC terpolymers are a class of very important polymers because of their expansive molecular topologies and extensive architectures. As block A, poly(ethylene glycol) (PEG) is one of the most principal categories owing to good biocompatibility and wide commercial availability. More importantly, the synthetic approaches of ABC terpolymers using PEG as a macroinitiator are facile and varied. PEG-based ABC terpolymers from design and synthesis to applications are highlighted in this review. Linear, 3-miktoarm, and cyclic polymers as the architecture are separated. The synthetic approaches of PEG-based ABC terpolymers mainly include the sequential polymerization or coupling of polymers. PEG-based ABC terpolymers have wide applications in the fields of drug carriers, gene vectors, templates for the fabrication of inorganic hollow nanospheres, and stabilizers of metal nanoparticles.

Scheme 1. Synthesis of ABC terpolymers via (a) the sequential RAFT polymerization, (b) Suzuki reaction, ROP, ATRP, and click coupling.

Fig. 1. Topology of PEG-based ABC (linear, 3-miktoarm, cyclic) terpolymers.

Fig. 2. Synthetic route for the preparation of PEG-based ABC linear terpolymers via (a) the sequential polymerization, (b) polymerization followed by coupling.

Scheme 2. Synthesis of PEG-based ABC linear terpolymers via the sequential (a) RAFT polymerization, (b) ATRP, (c) AROP, (d) CROP, and (e) a combination of CROP and ATRP.

Scheme 3. Synthesis of PEG-based ABC linear terpolymers via a combination of (a) ATRP and click coupling, (b) CROP and condensation reaction.

Fig. 3. Synthetic route for the preparation of PEG-based ABC 3-miktoarm terpolymers via (a) polymerization followed by coupling, (b) coupling followed by polymerization, (c) one-pot polymerization and coupling, and (d) coupling.

Scheme 4. Synthesis of PEG-based ABC 3-miktoarm terpolymers via a combination of (a) ATRP and click coupling, (b) ATRP and molecular recognition.

Scheme 5. Synthesis of PEG-based ABC 3-miktoarm terpolymers via coupling followed by polymerization.

Scheme 6. Synthesis of PEG-based ABC 3-miktoarm terpolymers via one-pot polymerization and coupling.

Scheme 7. Synthesis of PEG-based ABC 3-miktoarm terpolymers via coupling.

Fig. 4. Illustration depicting different morphologies produced by self-assembly of ABC linear or 3-miktoarm terpolymers. Reprinted with permission. Copyright (2012) American Chemical Society.

Fig. 5. Proposed structures and post-functionalization of micelles produced by self-assembly of ABC linear terpolymers. Reprinted with permission. Copyright (2016) American Chemical Society.

Fig. 6. pH-responsive polymeric micelles with tunable aggregation-induced emission and controllable drug release prepared from ABC linear terpolymers. Reprinted with permission. Copyright (2019) Springer.

Fig. 7. (a) Micelleplex self-assembled from PEG-b-PLA-b-R₁₅ with negatively charged siRNA by electrostatic interaction for siRNA delivery. Reprinted with permission. Copyright (2012) Elsevier. (b) Conjugation of siRNA to form ABC terpolymers for siRNA delivery. Reprinted with permission. Copyright (2013) Elsevier.

Fig. 8. ABC terpolymers used for the fabrication of inorganic hollow nanospheres. Reprinted with permission. Copyright (2014) American Chemical Society.

Fig. 9. Formation and catalytic reaction of ABC terpolymer-stabilized gold nanoparticles. Reprinted with permission. Copyright (2015) Elsevier.

Xiaojin Zhang

Yu Dai

Guofei Dai