ISSN:
0025-116X
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
In order to clarify the reaction mechanism of the solid-state polymerisation of 1,3,5-trioxane and 1,3,5,7-tetroxane as induced by gamma-radiation, the nascent textures and morphology of poly(oxymethylene) crystals were studied with light and transmission electron microscopy, X-ray scattering and differential thermal analysis techniques. In both cases poly(oxymethylene) crystals with fibrous morphology and “twin-structure” are obtained. The polymerization of 1,3,5,7-tetroxane gives rise to the formation of crystals where the preferred orientation of the polymer chain is the monomer b-axis; however, the fibrils showed ripples perpendicular to the main chain direction at a 70-240Å long period that depends extremely on the polymerization temperature. In the polymerization of 1,3,5-trioxane, POM crystals with 60% of the polymer chains in the direction of the monomer c-axis are obtained. The remaining chains are found in the “twin sub-crystals”. Dark field electron micrographs showed the sub-crystals to be an integral part of the fibrils. The material in the twin direction decreases, when the polymerization temperature or the yields increases; it never amounts to less than 30%. These results and the misfit between the lattices of the monomers and the nascent polymer indicate that the reactions which take place occur according to a simultaneous polymerization and crystallization mechanism through the gasphase. The polymerization process occurs easier at higher temperatures near the monomers' melting point due to the increase of monomer vapor pressure and diffusion processes in the monomer crystals. Molecular models of the chain growth are developed on the basis of the morphological observations.
Additional Material:
19 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1978.021790422
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