Polymerization-induced self-assembly of random bottlebrush copolymers†
Abstract
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 1H 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.