Polydiacetylenes crystal morphologies

The two-step process of epitaxial polymerization has been applied to symmetrically substituted diacetylenes First, the monomers have been crystallized epitaxially on alkali halides substrates from solution and the vapor phase. The oriented monomer crystals are then polymerized under the substrate s influence by gamma-irradiation. The diacetylenes in this study are 2,4-hexadiyn-l,6-diol (HD) and the bis-phenylurethane of 5,7-dodecadiyn-l,12-diol (TCDU). The polydiacetylene crystal structures and morphologies have been examined with the electron microscope. Reactivity and polymorphism are found to be controlled by the substrate. 

Morphology. In general,polydiacetylene single crystals are found in one of two crystal morphologies, either as lozenges or as fibres. 

Despite these problems a coherent picture of the properties of polydiacetylene crystals is emerging. It is, therefore, possible to use this as a basis for studies and interpretation of the properties of disordered samples. Again the polydiacetylenes provide model systems since the morphology of disordered samples can be controlled and characterized. Thus, in principle, the effect of particular types of disorder can be studied. This work is clearly of value in understanding the behaviour of polymers for which only disordered samples are available. Less effort has been expended on such studies but it is an area of growing interest,... 

The complex morphology of most conjugated polymers prevents direct measurement, and hinders understanding, of their intrinsic properties. Such problems do not occur for the polydiacetylenes, which can be prepared as macroscopic single crystals. Since polydiacetylenes can also be obtained in less perfect forms the effects of disorder can be studied. Spectroscopic techniques have been widely used to study the intrinsic properties of polydiacetylenes and their modification by disorder. The results obtained by optical and electron spin resonance spectroscopy are discussed. 

Polydiacetylenes. Single crystals of poly(TCDU) and poly— (DMDA) were deposited on a variety of alkali halide crystals. The resultant morphology of both the monomers and polymers were identical and were elongated platelets oriented in the substrates <110> directions (Figures 5 and 6). 

Young, R.J., R.T. Read, D.N. Batchelder, and D. Bloor. 1981. Stmcture and morphology of heavily deformed single crystals of a polydiacetylene. I. Electron microscopy and x-ray diffraction. J Polym Sci Polym Phys 19 293. 

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