Poly(indanes) can be prepared by the photoinduced cationic polymerization of a variety of diisopropenyl aromatic monomers. Typically, polymerization proceeds rapidly under UV irradiation catalyzed by diaryliodonium salt photoinitiators to give hard, transparent films. Investigations have shown that the polymerization proceeds mainly by a dimerization followed by a ringclosure process to yield indane structures along the polymer backbone. Film-forming mixtures containing either pure monomer or mixtures of monomers together with a poly(indane) prepolymer can be spin coated onto silicon wafers. Measurements made on the photopolymerized coatings give low dielectric constants. These coatings also display excellent thermal stability.