Synthesis Of Polyacrylonitrile Nanoparticles By Miniemulsion Polymerization

Polyacrylonitrile(PAN) spherical nanoparticles and PAN nanocapsules have diversepotential applications including separation process, carbon nano-sphere and catalyst carrier,owing to its special optic and mechanical properties. In this paper, both PAN sphericalnanoparticles and PAN nanocapsules were synthesized by miniemulsion polymerizationrespectively, and the nucleation mechanism and some influential factors of thepolymerizations were discussed as well.In order to achieve spherical PAN nanoparticles, the factors that affect droplet stability,nucleation mechanism as well as the morphology of PAN nanoparticles were analyzed,including the emulsifier, the costabilizer, the monomer concentration, the shear force and themonomer watersolubility. It was found that the most stable monomer droplets and dropletnucleation predominant as well as the spherical PAN nanoparticles were achieved under thecircumstance when the ultrasonic processor was operated at60%amplitude for5minuteswith a recipe that,8mM of sodium dodecyl sulfate (SDS) and Tween60at the ratio of7:3based on aqueous phase,4wt%of hexadecane (HD) based on total monomer amount and1.6mM of L-ascorbic acid (LAA) based on aqueous, where the molar ratio of H2O2and LAAwas9:1initiated at30℃. Moreover, it was found that the crystallinity degree and themorphology of PAN nanoparticles would varied with different kinds of nucleationmechanisms, according to the scanning electron microscope (SEM) tests of PANnanoparticles synthesized by miniemulsion polymerization with different kinds of initiators.Therefore, the nucleation mechanism can be estimated by the PAN particle morphology.Since HD and acrylonitrile (AN) is incompatible with PAN polymers, phase separationof PAN polymer chains would emerge in the synthesis of PAN nanoparticles by miniemulsionpolymerization, which makes the preparation of PAN nanocapsules possible. The PANnanocapsules were synthesized by miniemulsion polymerization. Furthermore, the factors thatsignificantly influenced the nucleation process of PAN nanocapsules, such as the initiatortypes, the initiator concentrations, the costabilizer types and the costabilizer concentrationswere analyzed. It was found that lower temperature was an obstruction of the movement andphase separation behavior of the PAN polymer chains, which made the potassium persulfate(KPS) more suitable than H2O2/LAA as the initiator of the synthesis process, that the stearylmethylacrylate (ODMA) was far more compatible with PAN polymers for it was softmonomer and it would copolymerize with AN monomer during the polymerization, which made the ODMA bad for the synthesis of PAN nanocapsules, that the PAN nanocapsules wereadopted with2mM of KPS as initiator and6wt%of HD (based on monomer concentration) ascostabilizer.