Preparation of core-shell dispersions with a low tg polymer core and a polyaniline shell

Core-shell particles with a filmforming (i.e. low tg) core and a shell of polyaniline have been prepared. During the preparation the pH, the potential of the reaction mixture and the temperature have been monitored. The concentration of aniline, dimer and benzidine have been measured with HPLC in samples taken at various reaction times. The lag-time which is usual for the formation of polyaniline could be observed by all these techniques. During this time many oligomers are formed as can be concluded from the colour of the reaction mixture and from several peaks in the HPLC data. However, the amounts of aniline, benzidine and dimer are constant during this time. After the lag time the reaction accelerates and the oligomers are built in the polyaniline chains. Certain quantities of benzidine and other products may remain in the dispersion, depending on the reaction conditions and the nature of the core particles. Using poly-urethane core particles benzidine free dispersions can be obtained.