Vinylcarbazole has been used in research labs since the early 1920’s. When produced from non-coal tar sources it is found to be most pure and typically is a more white/off-white crystalline solid. The final monomer has good solubility in polar organic, aromatic, and chlorinated solvents, with only minimal solubility in non-polar systems that are not aromatic.
A summary of key physical property and research information for vinylcarbazole –
Alternate names 9-vinyl-9H-carbazole; vinyl-9H-carbazole; N-vinylcarbazole
Molecular weight 193.24 g/mol
Melting point 65-66 oC
As indicated earlier, carbazole from coal-tar distillation is the main starting material for industrial synthesis of vinylcarbazole. Typically, vinylation of the carbazole in the presence of a metal hydroxide is arguably the safest industrial route. However, acetylene reactions with alkali metal salts are used by organizations that are allowed, and capable, of undertaking acetylene-based reactions. Acetylene reactions are very dangerous, even more so when undertaken at moderate to high pressures – needed in order to affect this route. Recently a slightly safer route using acetylene carbonate has been developed, but initial indications suggest a higher end cost per Kg of the material.
Laboratory preparations have the advantage of using more expensive starting materials and more elegant chemistry. This in turn allows the production of N-vinylcarbazole that may be purer, and free of the impurities that exist with coal-tar sourced vinylcarbazole. An example synthesis is the dehydration of N(2-hydroxyethyl)carbazole which is obtained by the reaction of potassium carbazole with 2-chloroethanol. For the organometallic and catalyst chemists among us, PdCl2 has been used to effect ethylenation of carbazole starting materials. These laboratory synthesis methods are important for scientists who need very high purity material. When researching N-vinylcarbazole production researchers should be careful to determine the source of their material as it may impact their results. Some key impurities from coal-tar distillation include sulfur compounds, aromatics and polyaromatic rings such as anthracene.
One synthetic and handling note – Always read the material safety data sheet for full information, but take prior note that vinylcarbazole should be handled with care because it may cause skin irritations and is believed to be carcinogenic.
There are many methods for the polymerization of vinyl carbazole, including radical polymerization, cationic polymerization, charge-transfer polymerization, solid-state polymerization. Each of these utilizes very different conditions and initiators, ultimately resulting in a wide variety of polymer properties. The overriding goal is to produce a homo- or co-polymer of vinylcarbazole. Poly(vinylcarbazole), or PVK, polymers are well known for their thermal stability and optoelectronic properties when doped.