Study on pore size distributions of microporous polymer membranes having different physical architecture using capillary flow porometry

Capillary flow porometry (CFP) is an emerging technique to measure the most constricted part of the through pores in membranes. In our previous work, the technique was successfully tested for track-etch membranes, which are model membranes with straight cylindrical pores. In this work, this technique has been used to measure the mean pore size, smallest pore size, and bubble point pore size for commercially available microporous membranes such as poly(propylene), poly(ethersulfone), poly(tetrafluoroethylene), and poly(vinylidene fluoride). The scanning electron microscopy images revealed that these membranes have different microporous architecture with no well-defined pores in these membranes. The study is important because the pore architecture in these membranes is not straight and cylindrical, as assumed by CFP. Also, the influence of different parameters such as the shape factor, wetting liquid, and tortuosity on the performance of capillary flow porometer has been studied. It is seen that it is important to incorporate shape factor for CFP measurements of membranes with such pore architecture for obtaining the reliable results. The studies with different wetting liquids (Porefil, dodecane, and 1-decanol) show that for the membranes studied, dodecane can serve as a wetting liquid to obtain information about membrane pore sizes, without much effect on the results. The technique has been applied to measure the pore size distribution of highly cross-linked poly(vinylbenzylchloride) pore-filled membranes synthesized in our laboratory.