Rational Design of Functional Bottlebrush Polymers for Polylactide Blends with Improved Toughness and Antibacterial Performance.

A series of bottlebrush polymers was rationally synthesized using norbornene-functionalized polylactide (NB-PLA), polycaprolactone (NB-PCL), and quaternized poly(2-(dimethylamino)ethyl methacrylate (NB-QPDM) via ring-opening metathesis polymerization (ROMP). These polymeric additives enabled the simultaneous improvement of toughness and antibacterial activity in PLA blends. Incorporating 10 wt % of P34, which consists of NB-PLA, NB-PCL, and NB-QPDM with backbone degrees of polymerization of 6, 34, and 4, respectively, led to a significant increase in tensile toughness while maintaining the tensile strength and Young's modulus comparable to neat PLA. This enhancement could be ascribed to the combined effects of a dispersed toughening phase and a weak physical network structure. Furthermore, the PLA blend containing P34 exhibited outstanding antibacterial efficacy of 99.5% against E. coli, which originated from the presence of a quaternary ammonium group.