ABSTRACT
The spiro ortho carbonates are the most promising class of expanding monomers to date, mainly because of their large volume expansion upon polymerization. A better mechanistic understanding exists for the spiro ortho esters, which also have the virtue of relatively easy synthesis. Expanding monomers are being produced commercially in both the US and in Japan. Among the substances available in commercial quantities are spiro ortho carbonates and unsaturated spiro ortho carbonates. There are several products of industrial importance that could benefit from the incorporation of expanding monomers. The technology of expanding monomers is still in its infancy and the subject of ongoing research and commercialization. Undoubtedly, costs of such monomers will undergo dramatic reduction concurrently with an improvement in properties and volume expansion. Expanding monomers should provide more void-free polymers than conventional materials. These void-free polymers must have electrical properties, such as dielectric loss and dielectric constant, at least as good as the conventional polymers they are intended to replace.
