Polymerization-induced self-assembly of random bottlebrush copolymers

Bottlebrush polymers have shown unique self-assembly behaviors, providing access to hierarchical nanoparticles with a precise structure and tailorable function. However, the self-assembly pattern of random bottlebrush copolymers (random BBCPs) is still unclear due to the complexity of their synthesis and the kinetic barriers of the conventional solution self-assembly methods. Herein, RAFT-mediated polymerization-induced self-assembly (PISA) was exploited to evaluate the self-assembly behavior of amphiphilic random BBCPs. P[PEGMA-co-(HEMA-g-PS)] random BBCPs with tailored lengths of backbone and side-chains were synthesized via RAFT dispersion polymerization using a hydrophilic bottlebrush as the chain-transfer agent (CTA). The structural characteristic of the as-formed amphiphilic random BBCPs was confirmed by H-1 NMR, and the assemblies were examined by DLS and TEM. PISA of these random BBCPs resulted in spherical micelles, whose hydrodynamic size increases with the growth of the hydrophobic PS side-chains. Furthermore, the micellar core size was correlated with the chain length of PS via a scaling law, which revealed that the hydrophobic side-chains become increasingly stretched, and the segregation strength between PPEGMA and PS side-chains increases with the backbone length of random BBCPs.