Dual Stimuli‐Responsive Ternary Core‐Shell Polystyrene@Pnipam‐Pedot Latexes

Abstract

Abstract The ability of stimuli‐responsive materials to respond to external stimuli depends on their intra‐ and intermolecular interactions, which, in turn, are governed by changes in the material composition. Here, the importance of these factors for new heat and light‐sensitive latexes of core‐shell nanoparticles is reported with the polystyrene core, the poly(N‐isopropylacrylamide) (PNIPAM) shell containing doped poly(3,4‐ethylenedioxythiophene) (PEDOT). It is found that hydrogen bonding, C═O─π aromatic, hydrophilic‐hydrophobic interactions in the shell cause conformational changes in PNIPAM similar to those occurring in the PNIPAM coil‐globule transition. Depending on the EDOT:PS@PNIPAM feed ratio and the PEDOT content in PNIPAM shells, these interactions and changes affect nanoparticle sizes and are responsible for shifting the lower critical solution temperature (LCST) of PNIPAM in the shell from 32.1 to 33.9 °C. The core‐shell morphology of nanoparticles is maintained only for latexes with EDOT feed to ≈9 wt.%. At the higher EDOT content, PNIPAM shells are destroyed. Synthesized PS@PNIPAM‐PEDOT latexes demonstrate temperature‐dependent behavior and produce a photothermal effect under NIR irradiation, which allows for a rise of their temperature above LCST. This dual stimuli (heat and light) responsiveness suggests an important possibility for these latexes to be used for drug or diagnostic agent delivery.