In this paper, we describe the thermal and spectroscopic analysis of copolymers containing sequential thioethylene units. Room-temperature analysis of copolymers confirms structures similar to poly(thioethylene) (PTE) for the thioethylene segment in copolymers with oxyethylene spacers. With poly(methylene) spacers, the overall conformation along the polymer chain is different from that of PTE, leading to different crystal packing and reduced melting points. DSC shows multiple transitions for the oxyethylene copolymers. Variable-temperature spectroscopic analysis indicates a nonconcerted conformational disorder in the rigid regions of the oxyethylene copolymers at temperatures well below both DSC submelting and melting transition temperatures. Reorganization involving crystal thickening may be occurring at intermediate DSC exotherms seen just before the final melting endotherm. Conformational disorder occurs sooner and to a greater extent in sequential copolymers in which the spacer group consists of poly(methylene) units rather than oxyethylene between thioethylene segments, and there is reduction or absence of the premelt transitions in many of these samples.