<p>Sequence-specific conformational changes underpin essential biological processes, from information storage to energy transduction, but are difficult to replicate in synthetic systems. Here, we present a simple approach to encode in the primary sequence of molecular strands all the information required to govern both the formation and dynamic behavior of multistranded helices. We demonstrate that the sequence of oligo(<i>m</i>-phenylene ethynylene) strands composed of hydrophobic phenylene and charged pyridinium residues reliably direct the formation of either a single structure (e.g., a double helix) or dynamic assemblies (e.g., double and triple helices in exchange). In the latter case, transitions between different helical states can be controlled by concentration, temperature, or by the presence of anionic molecules. This minimal yet versatile design strategy lays the groundwork for the construction of adaptive supramolecular systems with programmable structure and function.</p>