Research Topic

Bottlebrush polymers (BBP) feature polymeric side chains grafted to a linear backbone. Compared to linear polymers, BBPs have unique physical characteristics due to their densely grafted polymeric sidechains attached to the polymer backbone. (1) The intramolecular excluded volume effect of sidechains can extend the backbone. (2) The extended conformation can suppress chain entanglement and magnify entanglement molecular weight (Me). (3) A large number of sidechain ends are present per BBP with a high spatial density. To utilize these unique characteristics, BBPs with various structures are synthesized.

Advances in living radical polymerization techniques have enabled the synthesis of BBPs with distinct structures. Various polymerization methods are utilized in the synthesis of BBPs, such as ATRP, RAFT polymerization, anionic polymerization, ROP, and ROMP. Our group specializes in polymer synthesis using these polymerization methods and has accumulated experience in the synthesis of BBPs. Based on these experiences, our group focuses on synthesis of BBPs and its application in diverse fields of science.

For application in energy storage devices, BBPs can be used as polymeric binders in lithium-ion batteries. For example, our group synthesized amphiphilic BBPs as cathode binders that can solve the current issues of commercialized PVDF binders. The amphiphilic BBPs are composed of a hydrophobic polynorbornene (PNB) backbone and a hydrophilic polyacrylic acid (PAA) side chain. The 3D structure of the BBP binder allow uniform distribution of the BBPs in the electrode and can maintain stable performance even after multiple charge and discharge cycles. The amphiphilicity of the BBP binder was effective in suppression of swelling due to the electrolyte and effective adhesion with not only the active material, but also the aluminum current collector.

Due to the suppression of chain entanglement, BBPs can also be used as additives in linear polymers. Because entanglement of BBPs is suppressed due to the intramolecular excluded volume effect of sidechains, BBPs possess much lower viscosity compared to linear polymers with the same molecular weight. As a result, BBPs can be used as viscosity modifier additives that can lower the viscosity when blended with linear polymers. Poly(lactic acid) (PLA) is a biodegradable polymer that has high industrial value, but currently the use of PLA is limited due to its high viscosity. Our group focuses on synthesis and utilization of various BBP additives that can act as viscosity modifiers of linear PLA. We expect the BBP additives to increase the processability and utilization of eco-friendly polymers such as PLA and PBAT.