We report a study on the mechanical properties of lamellae-forming glassy-semicrystalline block copolymers composed of poly(cyclohexylethylene) (C) and polyethylene (E). Tensile properties of polydomain CEC, ECEC, CECEC, and ECECE block copolymers, and blends of these materials, reveal a critical dependence on the connectivity of the semicrystalline E blocks. A molecular parameter directly related to the fraction of bridging E blocks is identified, which captures the fracture behavior of C/E block copolymers over a range of chain architectures. Tensile testing and small-angle X-ray scattering (SAXS) experiments on aligned block copolymers reveal the role of bridging in the glassy C block and further elucidate the mechanisms that govern the deformation of microphase-separated lamellar domains and macroscopic fracture in glassy-semicrystalline block copolymers.