Year

1997

Degree Name

Doctor of Philosophy

Department

Department of Chemistry

Abstract

The development of new materials has greatly expanded the application of membrane separation technologies. Conducting electroactive polymers, such as polypyrrole, represent a new class of electrodynamic membranes with potential application in a number of areas.

A range of new electromembranes have been successfully synthesised and characterised in this work. A new electromembrane transport systems for protein separation and recovery has been devised.

Platinised electromembranes have been successfully fabricated with the use of conventional commercial membranes such as polyvinylidine fluoride (PVDF) or polysulfone membranes as substrates. Polypyrrole composite membranes as well as free-standing films have been electrochemically synthesised with a series of counterions of different molecular weights and biofunctional groups.

Electrochemically controlled protein transport and separation have been carried out with both platinised PVDF membranes and polypyrrole coated platinised PVDF composite membranes. Results show that the transport of test proteins across membranes can be electrochemically manipulated by controlling the stimuli applied to the membranes. In addition, the transport/separation of two proteins of different isoelectric points has been demonstrated with both the stationary transport cell and a flowthrough cell. Separation factors of 70 were obtained for BSA over haemoglobin.

The incorporation of biofunctional groups into polypyrroles has been achieved using electropolymerisation. Interactions between test proteins, such as human serum albumin (HSA) and thrombin, with polypyrroles have been investigated using the Electrochemical Quartz Crystal Microbalance (EQCM). The binding of thrombin to polypyrrole-heparin was shown to be selective.

Studies into gas separations using polypyrrole conducting polymer membranes were also carried out. The oxygen and nitrogen permeation rates of polypyrrole membranes varied depending on the type of counterion incorporated into the polypyrrole. Polypyrrole prepared with conventional counterions such as p-toluene sulfonate have higher permeation rate for nitrogen then that for oxygen when tested with pure gas. Polypyrrole-polyaniline sulfonate was found to have higher oxygen selectivity over nitrogen with 02:N2 of 3~6:1 obtained. Polypyrrole membranes prepared with polyanions show no selectivity because of their high porosity. The separation of gas mixtures was carried out using air as the feed gas.

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