Synthesis of quaternary fluoroalkyl phosphonium salts with high thermal stability and their application as antibacterial agents for polycarbonate (PC)

Two kinds of quaternary fluoroalkyl phosphonium salts with different fluoroalkyl chain length were synthesized as antibacterial agents for polycarbonate (PC). Both of these quaternary fluoroalkyl phosphonium salts had sufficient thermal stability under PC processing temperature, and the quaternary fluoroalkyl phosphonium salt with shorter fluoroalkyl chain length was chosen for adding into PC because of its better antibacterial activity. The influence of quaternary fluoroalkyl phosphonium salt concentration on mechanical properties, thermodynamic properties, light transmittance, and antibacterial activity of PC were investigated. The results showed that the chosen quaternary fluoroalkyl phosphonium salt had good compatibility with PC, and had no negative effect on flexural strength, tensile strength, and impact strength of PC. Due to the plasticization effect of small molecules, the modulus and Tg of PC were reduced, but the melt flow rate was increased. After adding 2 wt% of quaternary fluoroalkyl phosphonium salt, no matter before or after 1 month of water immersion, the obtained PC could have more than 90% of antibacterial rate against both Escherichia coli and Staphylococcus aureus. The agar diffusion test indicated that the antibacterial activity of PC was not dependent on the leaching of quaternary fluoroalkyl phosphonium salt. However, the quaternary fluoroalkyl phosphonium salt could reduce light transmittance of PC and dye PC because of high electronic density and oxidation of iodine.