Photoinitiation, in polymerization

The photopolymer office copy system, however, had shown that HABIs could be effective photoinitiators in polymeric systems and provided stable, almost colorless and readily modifyable components. Exploratory work by G. R. Nacci, J. E. Pazos, and others showed just what possible ways there were to utilize effectively these then novel photoinitiators. This work inevitably focused on the use of o-Cl-HABI, which was the least expensive hexaarylbiimidazole that possessed the requisite stability and absorption spectrum. By the time that the photopolymer applications became commercially important, the Dylux Venture had been terminated, and there was essentially little interest in synthetic work to produce still more effective photoinitiators of this family. 

Diazonium salts, relatively stable to heat, have been used as photoinitiators in polymerization processes. Both phenyl cations and radicals generated during the illumination stage will initiate polymerization of vinyl ethers and the crosshnking of low-molecular-weight polymers with reactive alkene substituents. ... 

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