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The ACS PRF starter grant allowed me to get my research up and running quickly upon arriving at Penn State.  The boost in funding and affirmation of our ideas by peer review facilitated a rapid start to graduate student work in my lab.  The most important impact of our research is the demonstration of formation of thin active layers of poly(aniline) on microporous supports and the control of its permeation properties by selective doping.  Importantly, with the ACS PRF funding, we were able to purchase a scanning

Figure 1.  (a) glucose permeability of nanoporous polyaniline membranes as a function of doping level; (b) increase in SANS intensity with doping ratio indicating increase in nanoporosity with doping.

Raman spectrometer, which will have long-lasting impact our research program involving the transport through permselective membranes.  The Raman spectrometer will be used as a detector for analytes in transport experiments as well as for measuring membrane degradation as a function of time.

A significant result of our work with PRF funds is shown in Figure 1(a) where the selective transport through a poly(aniline) membrane is shown as a function of doping ratio.  Thin film poly(aniline) membranes were cast with different doping levels of camphorsulfonic acid (CSA).  The membranes were then dedoped and their glucose permeability in aqueous solution measured.  We have demonstrated that the glucose permeation is a function of the doping ratio in these types of systems.  We hypothesized that the doping ratio controls the nanoporosity of the poly(aniline) films and thus by changing the doping ratio, we may able to change the porosity of the film.  Small-angle neutron scattering was performed on the dedoped films.  As shown in Figure 1(b), the SANS intensity increases with an increase in doping ratio.  The increase in SANS intensity is an indication that the films are becoming more porous upon dedoping.  This data demonstrates that the increase in membrane permeability is directly affected by the porosity of the dedoped film.  These results are unique compared to previous work in selective separations by poly(aniline) active layers because we have been able to make measurements of the physical size of the pores formed upon dedoping and we have connected the pore structure to the permeation properties.  Also, the thin-film active layer membrane format developed in this work allows the flux of the membranes to be rather high, compared to other examples of poly(aniline) membranes that have been 50-100 mm thick.

We hope to extend these results to other dopant molecules.  Experiments were performed in organic permeant solutions with small molecules, akin to what might be expected in a petroleum processing separation, but no selective separation was observed with camphorsulfonic acid as a dopant.  It is thought that the cavities formed in the films with CSA are too large to affect selective separations for small molecules.  Regardless, the concept of connecting the size of the cavities and doping ratio to the membrane flux has been established.  The work funded by the PRF has established this motif in our lab for further work and allowed us to get preliminary data to attract future funding and has contributed part of the funding for a new instrument which will have long-term benefits for our research in membrane separations.