화학공학소재연구정보센터
Journal of the Chinese Institute of Chemical Engineers, Vol.32, No.1, 13-22, 2001
Effect of sputter coating on the observation of polymeric membrane structure
In the present work, the effect of sputter coating, a step for preparing SEM specimen, on the observation of polymeric membrane structure was investigated by using AFM to examine the difference in membrane structure before and after sputter coating. It was observed that the sputtering process can produce coatings made up of distinguished particles. The size of the particles is on the same order of that of nodules (20 nm), which are believed by many as a basic structure of polymeric membranes. Hence, the sputter coating could affect the judgement if nodules exist in a system and influence the determination of the size of nodules. In addition, it was found that, for three PMMA membranes studied in this work, the surface is not uniform but consists of a lot of protrusions, which is believed to be aggregations of polymer (nodules). For membrane surfaces with small crevices among protrusions, it seems that the protrusions receive more coatings than the crevices during coating process, resulting in larger surface protrusions after sputter coating. On the other hand, for membrane surfaces with large crevices among protrusions, the crevices would be filled with the coating material, resulting in smaller crevices after sputter coating. The results indicate that one should be careful in using SEM to investigate the fine polymeric structure such as nodules because the coating process could influence the fine structure.