Polyimide/polystyrene nanocomposite films as membranes for gas separation and precursors for polyimide nanofoams - Polyimides and Other High Temperature Polymers - page 482

of voids does not correspond to the volume fraction of polystyrene-based nano-
spheres in the initial composite films. In comparison with the initial volume frac-
tion of PS-based nanospheres in the composite, the increase in volume fraction of
voids incorporated into the matrix can also be understood by considering the
“blowing” effect. From the experimental results and corresponding discussion
above, we can deduce that the elimination of agglomeration and a relatively low
decomposition temperature for the nanospheres will give foams with pores of
nanometer size and without interconnection.

4. SUMMARY

PI nanocomposite films with gas permeability and permselectivity regulatable by
their composition were prepared in our laboratory by in-situ condensation polym-
erization in the presence of PS or PSVP nanospheres as templates. As the contents
of PS templates increased, the gas permeabilities increased while permselectivi-
ties decreased, compared to the increase of both permeability and permselectivity
for PSVP-based PI nanocomposite films. As regard to the dielectric property of PI
nanofoams, an increase the content of templates would decrease the dielectric
constant. TG analysis showed that the resulted PI nanofoams were thermally sta-
ble.

Acknowledgements
This work was supported by the National Natural Science Foundation of China
(Grant No. 59703005). Partial financial support for this work from the Foreign
Relation Office of the Technical University Berlin is also acknowledged.

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