Rational Design of Architectured Amphiphilic Block Copolymers and Polymer-Ligated Nanocrystals for Energy Storage and Drug Delivery

Abstract

Architectured amphiphilic block copolymers with complex molecular structures have garnered much attention in recent years due to their distinct chemical and physical properties compared to the linear counterparts. The amphiphilic chemical environment provides a robust platform for site selective functionalization as well as molecular interactions. Notably, architectured amphiphilic block copolymers can be employed as nanoreactors for crafting polymer-ligated nanocrystals. Specifically, the hydrophilic blocks of architectured amphiphilic block copolymers can be selectively loaded with metal precursors to achieve confined growth of inorganic nanocrystals. The size and shape of as-synthesized polymer-ligated nanocrystals can be precisely tailored via architectural design and controlling the reaction time of architectured amphiphilic block copolymers. Three architectured amphiphilic block copolymers (star-shaped, bottlebrush-shaped, and Janus star- shaped) are rationally designed and synthesized by capitalizing on multifunctional glucose-based biomolecules, either β-cyclodextrin (β-CD) as the core (for star- and Janus star-shaped) or cellulose as the backbone (for bottlebrush-shaped). These architectured amphiphilic block copolymers are synthesized through atom transfer radical polymerization and/or reversible addition-fragmentation chain-transfer polymerization, thereby possessing precisely controlled molecular weight and low polydispersity (PDI). These characteristics render them perfect polymeric nanoreactors for the synthesis of plain nanoparticles, nanorods, and spherical Janus nanoparticles. Specifically, first, poly(styrene-co-acrylonitrile)-ligated MFe2O4 nanoparticles crafted from star-shaped block copolymer nanoreactors display superior rate and cycling performance in lithium/sodium ion batteries when applied as anode. The surface poly(styrene-co-acrylonitrile) ligands can not only transport Li+ but also act as efficient physical barrier to prevent phase coarsening. Second, a robust crosslinking strategy via UV-initiated azide homocoupling is developed to readily convert azide-functionalized bottlebrush-shaped block copolymers into polymeric cocoons, exhibiting 3-fold encapsulation, 3-fold release time, and modulated release rate compared with non-crosslinked counterpart. Additionally, CsPbBr3 nanocrystals synthesized from the bottlebrush-shaped block copolymer nanoreactors possess much higher water, UV, and thermal stabilities in comparison to conventional aliphatic ligand-capped CsPbBr3 due to permanent ligation of polymer hairs as a dense protection layer. Finally, Janus star-shaped block copolymers are rationally synthesized which can readily structure-direct the growth of strictly biphasic Janus nanoparticles.