Hyperbranched Polymer Induced Antibacterial Tree‐Like Nanofibrous Membrane for High Effective Air Filtration

The air filtration materials with high efficiency, low resistance, and extra antibacterial property are crucial for personal health protection. Herein, a tree‐like polyvinylidene fluoride (PVDF) nanofibrous membrane with hierarchical structure (trunk fiber of 447 nm, branched fiber of 24.7 nm) and high filtration capacity is demonstrated. Specifically, 2‐hydroxypropyl trimethyl ammonium chloride terminated hyperbranched polymer (HBP‐HTC) with near‐spherical three‐dimensional molecular structure and adjustable terminal positive groups is synthesized as an additive for PVDF electrospinning to enhance the jet splitting and promote the formation of branched ultrafine nanofibers, achieving a coverage rate of branched nanofibers over 90% that is superior than small molecular quaternary ammonium salts. The branched nanofibers network enhances mechanical properties and filtration efficiency (99.995% for 0.26 µm sodium chloride particles) of the PVDF/HBP‐HTC membrane, which demonstrates reduced pressure drop (122.4 Pa) and a quality factor up to 0.083 Pa−1 on a 40 µm‐thick sample. More importantly, the numerous quaternary ammonium salt groups of HBP‐HTC deliver excellent antibacterial properties to the PVDF membranes. Bacterial inhibitive rate of 99.9% against both S. aureus and E. coli is demonstrated in a membrane with 3.0 wt% HBP‐HTC. This work provides a new strategy for development of high‐efficiency and antibacterial protection products. A hyperbranched polymer with tunable positive quaternary ammonium salt groups is synthesized to serve as an additive for PVDF electrospinning, demonstrating enhanced jet splitting of spinning solution to generate hierarchical tree‐like nanofibrous membrane with branched ultrafine nanofibers with a high coverage rate over 90%, which delivers high filtration efficiency, low pressure drop, and excellent antibacterial activity for air filtration application.