Present microelectronic photoimaging applications employ onium salts for deep UV (I-line, 365 nm) photolithography. Since most onium salts do not absorb at this wavelength, photosensitizers are commonly employed. Polynuclear aromatic hydrocarbons are the most efficient known examples of electron-transfer photosensitizers for onium salts. However, they have serious drawbacks that limit their use, such as they are expensive, toxis, and poorly soluable in most reactive monomers and polymer systems.

As part of the continuing effort to reduce the environmental impact of various industrial chemical processes, there has been a strong emphasis in developing new methodology for the application and cure of organic coatings. While these ubiquitous materials are absolutely essential to modern life, they also constitute one of the primary industrial Sources of emissions of Volatile organic Solvents that contribute to air and water pollution.

In photoinitiated cationic ring-opening polymerization, the polymerizable substrate is subjected to irradiation with light for a brief period during which the photopolymerization must proceed essentially to completion. Consequently, only monomers that undergo very high rates of polymerization may be employed. Certain epoxide monomers display high reactivity in photoinitiated cationic polymerization and are suitable for such uses while most other undergo sluggish reaction and are not usable.

There are two basic classes of adhesives in widespread current use. The first class is pressure sensitive adhesives, such as are employed in adhesive tapes. The second class is reactive adhesives, used primarily for structural purposes. A long-standing problem with these types of adhesives is that they are unable of obtaining both a long working life and a rapid cure time.

Cationic polymerization is employed in many commercially important applications, including, for example, decorative and abrasion resistant coatings, printing inks, adhesives, fiber reinforced composites, microelectronic encapsulations, tan coatings, pressure sensitive adhesives, high performance aerospace composites, fiber optic coatings, stereolithography, photoresist and holographic recording media. The term UV cure has also been applied to such processes because the polymerizations are typically induced by light having a wavelength in UV region below about 450 nm.