Preparation and characterization of antibacterial poly(lactic acid) nanocomposites with N-halamine modified silica

In this work, silica nanoparticles modified with a new N-halamine precursor (EBDMH-SiO₂ NPs) were synthesized through immobilization of 3-(4'-epoxyethyl-benzyl)-5,5-dimethylhydantoin (EBDMH) on the surface of amino-functionalized silica NPs. Then, EBDMH-SiO₂ NPs and poly(lactic acid) (PLA) were blended at 185 °C to prepare a novel environmentally friendly PLA based nanocomposite (PLA/EBDMH-SiO₂). The addition of EBDMH-SiO₂ NPs has great influences on the thermal properties of nanocomposite. DSC results show that the grass transition temperature (T_g), cold crystallization temperature (T_cc) and melting temperature (T_m) of PLA in nanocomposites gradually decrease with the increase of EBDMH-SiO₂ NPs contents up to 5%. After that, further rise in EBDMH-SiO₂ NPs content actually increases T_g, T_cc, and T_m. The overall crystallization and spherulite growth rate of PLA show the similar trend. Furthermore, the introduction of EBDMH-SiO₂ NPs increases the storage modulus and viscosity of the melt of nanocomposite, providing an additional benefit for PLA blowing and injection molding. After chlorination, the N-halamine precursors on the nanocomposite surfaces are transformed into N-halamines, which provide strong antibacterial activities against E. coli (CMCC 44103) and S. aureus (ATCC 6538), pointing to good potentials of the PLA/EBDMH-SiO₂ nanocomposites for antibacterial applications including food packaging, filters, and a wide range of hygienic products.