Rigid Networks with Triazine Branchpoints

The isomeric 1,3,5-triazine-1,3,5-triazines, called isocyanurates, lost the o 

5-triazine rings may be introduced into a network in their preformed state, as in the case of melamine, or may be formed in place by cyclotrimer-ization of the appropriate monomers [523]. Thus, by the trimerization of 4,4 -dicyanobiphenyl 

The cyclotrimerization of aromatic dicyanato monomers to create highly aromatic network with cyanurate branchpoints is far more prevalent. In a typical reaction, monomers such as 2,2-bis(4-cyanatophenyl) propane are heated in the presence of a catalyst to form a network  

A variety of organic salts [533], organometallic [534] and other compounds [535, 536] may serve as catalysts for the trimerization. Because trimerization was found to be the dominant reaction, and dimerization less than 1% [533, 537], the network fragment shown above may be taken as a true representation of the final network product. 

It appears that 1,3,5-triazine branchpoint polymers with the shortest identical length segments are those made from bisphenol derivatives. Commercially available monomers that may be polymerized to a network through trimerization brought about by heat curing in the presence of an appropriate catalyst, are 2,2-bis(4-cyanatophenyl) propane, 1,1-bis (4-cyanatophenyl) ethane 

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