The present invention relates generally to high sulfur content polymeric materials and composites, methods for making them, and devices using them such as electrochemical cells and optical elements. In one aspect, a polymeric composition comprising a copolymer of sulfur, at a level in the range of at least about 50 wt % of the copolymer, and one or more monomers each selected from the group consisting of ethylenically unsaturated monomers, epoxide monomers, and thiirane monomers, at a level in the range of about 0.1 wt % to about 50 wt % of the copolymer.