Embodiments in accordance with the present invention encompass compositions comprising a organopalladium compound, a photoacid generator, a photosensitizer, one or more olefinic monomers and a stabilizer, such as for example a hindered amine, which undergo vinyl addition polymerization when said composition is exposed to a suitable actinic radiation to form a substantially transparent film. The compositions of this invention are stable at room temperature for several days to several months and can also be stored at higher temperatures from about 40° C. to 60° C. for several days and undergo mass polymerization only when subjected to suitable actinic radiation. The monomers employed therein have a range of optical and mechanical properties, and thus these compositions can be tailored to form films having various opto-electronic properties. Accordingly, compositions of this invention are useful in various applications, including as coatings, encapsulants, fillers, leveling agents, sealants, adhesives, among others.