Abstract
Well-oriented crystalline samples of syndiotactic poly(methylmethacrylate) (st-PMMA) could be prepared from stretched non-crystalline samples on solvent-induced crystallization using chloroacetone, diethyl ketone, etc. as the solvent. X-ray fibre diagrams of these samples usually show period of 35.4Å and also suggest that the st-PMMA chains have a helical conformation of large radius and small axial pitch along the original stretched direction. Inversion of dichroism for most infra-red absorption bands during the crystallization, which is an indication of a wide variation in the orientation of the chains, again supports the large helical conformation. It was also confirmed that the solvents are necessary in maintaining the crystalinity as the samples lose crystallinity on desorption of the solvents. From these results, it is conceivable that st-PMMA forms a complex with the solvents similar to the well-known amylose-iodine complex.
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