Preparation of nanoparticles of polystyrene and polyaniline by γ-irradiation in lyotropic liquid crystal

Abstract

Alkyl polyglucoside, commercially known as GP215 CS UP, is a non-ionic and biodegradable surfactant. When added to water and/or medium and long chain alkanes, it gives cubic, hexagonal and lamellar liquid crystalline phases. Using γ-irradiation technique, nanoparticles of polystyrene (PS) and polyaniline (PANI) have been prepared in the different lyotropic liquid crystalline phases of this amphiphile as a template. The templated lamellae of both polymers are almost identical. The rod-like nano-polystyrene particles obtained from the lamellar phase are 79.0 nm in width and 289.0 nm in length having an aspect ratio of 3.7 whereas the nanoparticles of polyaniline are 84.0 nm in width and 236.0 nm in length with an aspect ratio of 2.8. The hexagonal nanoparticles of the two polymers extracted from the hexagonal phase also show some similarity; nevertheless, the cubic-templated nanoparticles of polystyrene and polyaniline display different morphology under transmission electron microscope (TEM). Cube-like particles of polystyrene have a mean size of approximately 78.0 nm; in contrast, globe-like nano-polyaniline has more or less an average size of 70.0 nm. A time-resolved scanning electron microscope study of the polymeric growth reveals that the particle size of polystyrene increased from around 32.8 nm to 1.25 μm with increasing γ-irradiation dose (or conversely with increasing dose time). We discovered that the particles get increasingly monodisperse in the larger size range, i.e., for larger γ-doses. The TEM micrographs reveal striking resemblance between the different nanometer-sized polymeric templates and the underlying mesostructures. Polarizing light microscopy, X-ray small angle scattering (SAXS), and rheological measurements are used for the identification and characterization of the various mesophases and mesostructures with and without polymerization. SAXS, rheometry and electron microscope measurements are in good agreement.