Thermosensitive ternary core–shell nanocomposites of polystyrene, poly(N-isopropylacrylamide) and polyaniline

Abstract

We demonstrate synthesis and specificity of morphology, molecular structure and properties of new thermally sensitive latexes of the ternary core–shell nanocomposites with a core of polystyrene, shell of poly(N-isopropylacrylamide) (PNIPAM) embedded with nanoparticles of polyaniline doped by camphorsulfonic acid (PANI-CSA). We find that strong physical–chemical interactions in the shell between PNIPAM and PANI-CSA cause conformational changes in PNIPAM which are similar to those occurring during the PNIPAM coil-globule transition. These changes affect thermal responsivity of the synthesized latexes and are obviously responsible for the shift of the lower critical solution temperature (LCST) of PNIPAM in the shell from 32 °C (for the binary PS/PNIPAM latex) to 34 °C [for the ternary PS/PNIPAM/PANI-CSA(8.7 wt%) latex]. The synthesized ternary nanocomposites in the thoroughly dried (not swelled) state reveal low conductivity because of occluding and incomplete doping of PANI-CSA nanoparticles in the PNIPAM phase. However, when exposure to HCl vapor the conductivity increases by ca. 6 orders of magnitude that suggests their applicability as sensing materials for detection of analytes with acidic properties. The formulated PS/PNIPAM/PANI-CSA latexes not only demonstrate temperature-dependent flow behavior but due to their optical absorption in near-infrared (NIR) spectral range, can also produce a photothermal effect, which is revealed by a time-dependent rise of their temperature under irradiation with a NIR laser at 808 nm.