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Polysiloxaneimide(PSI) membranes with siloxane moieties in the
main chain were prepared by a polycondensation of pyromellitic
dianaydride(PMDA), 4,4'-oxydianiline(ODA) and amine-terminated
poly(dimethyl siloxane)(PDMS). The oxygen permeabilities of PSI
depend on the DMS contentand the different repeat units of DMS.
The oxygen permeabilities of different repeat units are in the
order of : P(repeat units of n=10) > P(repeat units of n=21) >
P(repeat units of n=40), at the lower DMS content. The gas
permeability and permselectivity of the PSI membranes are
similar to those of the polyimide component rather than of DMS
component. An opposite phenomenon appear at the DMS content
higher than 45 wt%, the gas permeability and permselectivity of
the PSI are similar to those of DMS component, the orders are
as follows: P(repeat units of n=40) > P(repeat units of n=21) >
P(repeat units of n=10). The effects of the DMS on
crystallinity, mechanical properties and thermal stability were
further investigated. Furthermore, thermodegradation of PSI was
investigated under nitrogen atmosphere at various heating
rates. When calculating kineticparameters, such as the
activation energy, the pre-exponential factorand the reaction
order, Ozawa's method was applied. Our results show that the
thermodegradation of such polymer occurs in two stages in a
nitrogen atmosphere. The kinetic order of degradation is
determined to be unity in the nitrogen atmosphere.
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