Hollow Polypyrrole Containers with Regulated Uptake/Release Properties

Polypyrrole microcontainers were successfully prepared by electrochemical polymerization of pyrrole on the surface of stainless steel electrodes. The size of the nanocontainers and the thickness of the polypyrrole shell (up to complete tilling of the container with grown polypyrrole) can be varied by changing both the scan speed of the electrode potential and potential range. Polypyrrole surfaces with high redox current due to their increased surface area are obtained; for optimized conditions, also microcontainers are obtained. The polypyrrole microcontainers with a size of less than 20 mu m can be easily detached from the electrode surface and polypyrrole films during several minutes of sonication in an ultrasonic bath. The polypyrrole shell of the microcontainers exhibits very strong barrier properties in acidic media at 2 < pH < 7 and a high permeability at pH > 7, providing effective encapsulation of low molecular weight species at low pH values.