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Polymerisations of N-vinylcarbazole have beeii carried out i n bulk and in suspension, t u provide a machinable material, a moulding powder and a novel foamed polymer. The dielectric properties of the polymer were found to be of the same order a s those of polystyrene, having a dielectric constant of 3.00 and a power factor of about 0.0010 over a wide frequency range but were more stable to changes of frequency and temperature; mechanically it is marginally inferior, but has a superior thermal stability. Experimental ApparatusB d k polyrncrisation equipment.-Small-scale bulk polymerisations (500 g.) were carried out in a ISZ-litre stainless-steel Baskerville autoclave heated by an external electric element.Part I : ,/. appl. Cliew., 1959, 9, 241

N‐Vinylcarbazole, when prepared from carbazole separated from coal‐tar fractions, did not show satisfactory polymerisation behaviour. This is due to sulphur‐containing impurities, and purification of the carbazole or of the vinylcarbazole has been only inadequate or unreproducible. The synthesis of carbazole from cyclohexanone and phenylhydrazine has been improved, and the vinylcarbazole obtained from such carbazole is low in sulphur and polymerises satisfactorily.

Polymerisations of N-vinylcarbazole have beeii carried out i n bulk and in suspension, t u provide a machinable material, a moulding powder and a novel foamed polymer. The dielectric properties of the polymer were found to be of the same order a s those of polystyrene, having a dielectric constant of 3.00 and a power factor of about 0.0010 over a wide frequency range but were more stable to changes of frequency and temperature; mechanically it is marginally inferior, but has a superior thermal stability.