LAMELLAR STRUCTURE OF POM SPHERULITES IMAGED BY A 2-STAGE RUO4 STAINING TECHNIQUE

Ruthenium tetroxide solution was prepared in situ by oxidation of ruth enium compounds at lower oxidation states with an excess of sodium per iodate. The solution was able to stain saturated polymer POM in the va por phase and it remained effective for up to 2 weeks. The melting beh avior of POM samples stained for different lengths of time was studied with DSC and the staining process was analyzed. The results indicated that ruthenium tetroxide affected both the amorphous region and the c rystals. During the early stage of the staining process, the tetroxide reacted preferentially with the amorphous material near the specimen surface. Much of this affected material was washed away after the rins ing process, thus resulting in an apparent increase in crystallinity. Prolonged staining would cause more crystals to degrade; hence, the cr ystallinity would drop. A two-step vapor staining technique was develo ped to improve the contrast between the amorphous and crystalline regi ons of ultrathin POM sections. The lamellar structure of POM spherulit es was revealed and examined under TEM. The results showed that POM sp herulites possess a category 2 structure and the thickness of the lame llae is about 7 nm. (C) 1996 John Wiley & Sons, Inc.