The Production Process of 4,4′-(1,4-Phenylenedi-2,1-ethenediyl)bis[benzonitrile]

4,4′-(1,4-Phenylenedi-2,1-ethenediyl)bis[benzonitrile], also known as PBN, is a highly sensitive and reliable polymeric initiator used in the production of various chemical products.
The production process of PBN involves several steps, which are carefully designed to ensure the highest quality of the final product.

Step 1: Preparation of the Monomer
The first step in the production process of PBN is the preparation of the monomer, which is a liquid mixture of 4,4′-dihydroxybenzophenone and 2,2′-dicyclohexyl-4,4′-dihydroxydiphenylmethane.
These two compounds are mixed together in a specific ratio, and the mixture is then treated with an alkaline solution to produce the mono-terminated monomer.

Step 2: Polycondensation Reaction
The next step is the polycondensation reaction, which involves the reaction of the monomer with benzene.
The reaction is carried out in the presence of a strong acid catalyst, such as sulfuric acid or phosphoric acid.
The reaction produces PBN, which is a liquid polymer with a high molecular weight.

Step 3: Purification of the PBN
After the polycondensation reaction is complete, the PBN is purified to remove any impurities that may have been introduced during the reaction.
This is typically done by washing the PBN with water and then drying it.

Step 4: Polymerization
The purified PBN is then subjected to a final polymerization step, which is designed to increase the molecular weight and improve the thermal stability of the polymer.
This step is typically carried out in the presence of a small amount of a solvent, such as toluene or xylene, and a small amount of a chain transfer agent, such as sodium dodecyl sulfate or a silane coupling agent.

Step 5: Recrystallization
After the polymerization step is complete, the PBN is allowed to cool and then filtered to remove any solid impurities.
The PBN is then dissolved in a suitable solvent, such as chloroform or ethyl acetate, and the solution is allowed to recrystallize.
This step is important for obtaining a pure and homogeneous PBN product.

Step 6: Characterization of the PBN
The final step in the production process of PBN is the characterization of the polymer.
This is typically done by analyzing the chemical composition, molecular weight, and thermal properties of the PBN using techniques such as gas chromatography, high-performance liquid chromatography, and thermogravimetric analysis.

Conclusion
In conclusion, the production process of PBN involves several steps, which are carefully designed to ensure the highest quality of the final product.
The process starts with the preparation of the monomer, which is a liquid mixture of 4,4′-dihydroxybenzophenone and 2,2′-dicyclohexyl-4,4′-dihydroxydiphenylmethane.
The monomer is then subjected to a polycondensation reaction with benzene, followed by purification, polymerization, and recrystallization steps.
Finally, the PBN is characterized to ensure that it meets the required quality standards.
The resulting PBN is a highly sensitive and reliable polymeric initiator that is widely used in the chemical industry.