Optimization of process parameters for preparing WO3/polyacrylonitrile nanocomposites and the associated dispersion mechanism

Polymer matrix nanocomposites is an emerging composite material into which nanoparticles are embedded in the polymer matrix. The degree with which the nanoparticles can be homogeneously dispersed in the matrix would significantly influence the mechanical and optoelectronic properties of the material. In the present study, polyacrylonitrile (PAN) was dissolved in N,N-dimethylformamide (DMF) to make a solution into which WO3 nanoparticles of size approximately 10 nm produced by the gas condensation method were introduced. The mixture was then homogeneously stirred by mechanical means to prepare the WO3/PAN nanocomposite. The Taguchi experiment method was employed to investigate to what degree associated with the dispersion of nanoparticles in the matrix were influenced by the various processing parameters. The results of the Taguchi experiments indicated that increased concentration of PAN demonstrated a positive effect on the uniform dispersion of the nanoparticles. It was also found that stirring speed had little contribution on how well the nanoparticles dispersed, which was substantiated with the observation that as the PAN concentration was increased to 80 g/l, the secondary WO3 nanoparticle size could be close to the single nanoparticle size approximately 11 nm. Conclusion was then drawn for the study that mechanism other than the one based on mechanical or stirring force was operative in dispersing the nanoparticles WO3 in PAN. Fourier transform infrared analysis performed for the composite material sample showed that shifting of peaks 785 and 930/cm took place when addition of WO3 nanoparticles in PAN was made. This suggests that interaction force between WO3 and PAN may be operative. Two possible modes for the interaction are proposed to account for the well-dispersion WO3 nanoparticles in PAN. The result also points out that PAN can function as an effective dispersant for promoting the dispersion of WO3 nanoparticles.