Synthesis of borneol-based cationic copolymer microspheres via a dual strategy of stereochemistry and cationic sterilization for antibacterial coatings

A series of borneol quaternary ammonium copolymer P(BO-StB) was synthesized through emulsion polymerization and characterized using 1H NMR, FT-IR, and scanning electron microscopy (SEM). Characterization results demonstrated that P(BO-StB) copolymers exhibited a favorable microscopic morphology, accompanied by excellent hydrophilicity (minimum water contact angle, θₘᵢₙ = 25.6 ± 3.7°) and a high surface zeta potential (maximum ζ potential, ζₘₐₓ = 31.1 ± 1.4   mV). Among the copolymer series, the optimal P(BO-StB) sample displayed the strongest antibacterial potency: it achieved an antibacterial rate of 99.9% against E. coli and 99.2% against S. aureus , with a minimum inhibitory concentration (MIC) of 6   mg/mL for E. coli and 3   mg/mL for S. aureus. In addition, P(BO-StB) also showed a statistically significant antibiofilm effect (P < 0.001). A proposed mechanism is that the electrostatic interaction between the cation and the bacteria facilitates the permeation of borneol into the cell membrane; furthermore, the stereochemical structure of borneol hinders bacterial adherence. Importantly, the use of polymers in coatings also fully leverages their antimicrobial benefits, offering novel alternatives for the development of antibacterial coatings.