Synthesis of tertiary amine functionalized Multi-Stimuli-Responsive latex nanoparticles by semicontinuous emulsion Polymerization: Investigation of responsivities and antimicrobial activity

Stimuli-responsive core–shell nanoparticles (CSNPs) are an important class of smart polymers, which their physical and chemical properties could be changed in response to induced external stimuli. In this study, the amphiphilic CSNPs were synthesized via semi-continuous seeded emulsion polymerization using dimethylamino ethyl methacrylate (DMAEMA) as a hydrophilic monomer, and styrene as a hydrophobic monomer. Developed CSNPs were obtained in two series, poly(N, N-dimethylamino ethyl methacrylate) (PDMAEMA)-polystyrene (PS) core–shell particles and PS-PDMAEMA core–shell particles. The PDMAEMA chains exhibited different responsivities towards temperature rising, pH change, and CO2-gas, which their smart behaviors were investigated by dynamic light scattering (DLS) analysis. The temperature-responsivity of CSNPs was confirmed by observed particle size variation in the case of PDMAEMA-PS (increase) and PS-PDMAEMA (decrease) core–shell latex particles, when temperature increased to 70 °C, above the lower critical solution temperature (LCST) of PDMAEMA. Protonation of tertiary amine functional groups in the presence of CO2 bubbling led to an increase in the size of CSNPs as a result of water swelling of PDMAEMA chains. On the other hand, the size of CSNPs was changed in acidic (pH = 4) and basic (pH = 10) media by swelling and deswelling of PDMAEMA located in the core or shell. Obtained results indicated that maximum antimicrobial activity was observed for PS-PDMAEMA CSNPs compared to PDMAEMA-PS, which is probably due to presence of the PDMAEMA on the surface and increase of positive charge related to amine groups in this sample. The developed antimicrobial latexes have potential applications for using as antibacterial additives in water-based coatings and adhesives.