Disclosed are photo or electron beam curable polymerizable compositions, and preparation thereof and devices containing such cured material. The composition contains completely or substantially completely hydrogenated hydrocarbon-based material completely free or substantially free of carbon-carbon double and triple bonds containing photo or electron beam curable terminal or pendant groups, low-outgassing photoinitiators, an optional viscosity adjustment component and an optional filler. The composition is visible light, UV or electron beam curable. It cures into a low-modulus, low outgassing polymer material. The composition can be used as an adhesive, sealant or lens potting material. It is ideal for use in lithographic tools and other optical devices involving deep or vacuum ultraviolet radiations, in particular, as lens potting materials for 248 nm, 193 nm and 157 nm lithographic tools, as well as other optical devices involving using high fluence irradiation.