Confocal laser scanning microscope analysis of organic–inorganic microporous membranes

The casting solution of an organic–inorganic microporous membrane was formed by dispersing a small quantity of fine alumina particles in a solution of poly(vinylidene fluoride) (PVDF) and dimethylacetamide (DMAC). The modified membranes were prepared by a phase inversion process and their characteristics (surface morphology and structures, surface roughness, porous dispersion, and the distribution of alumina particles) were compared to those of unmodified membranes (without alumina particles) using confocal laser scanning microscopy (CLSM). In order to analyze the membranes using CLSM, it was necessary to add trace amounts of fluorescein to all the samples to enable operation in the fluorescence mode. The inorganic alumina particles were found to be dispersed uniformly in the membranes. The results indicate not only that the organic-inorganic microporous membrane surface pore morphology changes but also that the pore dimensions and the surface roughness increase due to the addition of the alumina particles. At the same time, the study also shows that CLSM is an effective tool for investigating microporous membrane characteristics.