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Charged polymers are important for both biological and technological systems (examples?). Physically, charged polymers have interesting behavior due to the interplay between the length scale describing their intrinsic structural bending stiffness, and the length scale describing salt-dependent solution electrostatics. So, for example, the conformation of intrinsically-rigid double-stranded DNA (dsDNA) is only weakly dependent on salt, while the conformation of intrinsically-flexible single-stranded DNA (ssDNA) is very sensitive to salt. To investigate the interplay of structural rigidity and salt sensitivity, we are using methods of DNA nanotechnology to self-assemble polymers with a tunable intrinsic stiffness. To synthesize such a polymer, we used rolling circle amplification along with additional enzymatic procedures to produce block copolymers consisting of repeating tracts of dsDNA and ssDNA of known lengths. We then anchored each end of a single polymer, one to a glass coverslip and the other to a paramagnetic bead. The polymers were then stretched by the application of an external field, and the length as a function of applied force was extracted in various salt conditions. We have successfully tethered dsDNA/ssDNA copolymers and found their elastic behavior to be consistent with a polymer of intermediate stiffness. Qualitatively, we have found that the polymers become more flexible with salt, indicating that our approach is feasible. Thus we have laid the ground work for future in-depth studies of the salt dependent flexibility of charged polymers.