Tadpole-like bottlebrush polymer-modified multiwalled carbon nanotubes: A strategy for interface-strengthened polymer nanocomposites with exceptional performance

Nanocomposites incorporating hierarchically structured nanofillers create great opportunities to generate high-performance artificial materials. However, the rational design of the chemistry and structure of interfaces within polymer matrix is still challenging due to the intrinsic mismatch between nanofiller and matrix. Herein, we report an effective approach to fabricate chitosan (CS)-based nanocomposites with integrated high strength and toughness whose interfaces are chemically modulated by tadpole-like bottlebrush polymers (BBPs) modified multiwalled carbon nanotubes (MWCNTs). The tadpole-like PCL-b-(PCL-g-PGMA) BBPs, containing a bottlebrush poly(ε-caprolactone)-g-poly(glycidyl methacrylate) (PCL-g-PGMA) main body and a linear soft PCL tail, act as a bridge to connect the MWCNTs and CS matrix, resulting in the soft inner layer (PCL tail) and the stretchable cross-linked outer layer (PCL-g-PGMA main body) at the interface of the CS/MWCNTs-BBPs nanocomposite films. Significantly, unlike traditional block copolymers (BCPs) toughening with limited stretching spacing, the coupling of stretched PGMA brush and soft PCL backbone in PCL-g-PGMA main body impart the MWCNTs-BBPs with stretchable interfacial spatial distance when the MWCNTs bear stretching force. The resultant CS/MWCNTs-BBPs nanocomposite film with 1.5 wt% MWCNTs loading exhibits high tensile strength (up to 80.6 % increase), exceptional elongation at break (up to 380 % increase), and superior toughness (up to 976 % increase) in comparison with the neat CS. This study represents a new strategy for designing interface-strengthened nanocomposites with exceptional performance and holding great promise in a wide range of applications.