A range of doubly dynamic proteoid biodynamers based on the polycondensation of various categories of amino acid hydrazides with a dialdehyde have been generated through formation of two types of reversible C=N bonds (imine and acylhydrazone). Their structures and properties (rates of polymerization and dynamic character) have been characterized by NMR, small-angle neutron scattering, dynamic light scattering, and cryo-transmission-electron microscopy. Three types of structures (nanorods, globular nano-objects, oligomers) are obtained at different rates after polycondensation. Competitive polymerization shows that electrostatic effects markedly influence polymerizations when two oppositely charged monomers are used, and an exchange experiment demonstrates the preferential incorporation of a specific monomer in the biodynamer chain. Taken together, all our results show that the side chains of the amino acid hydrazides have a strong influence on the rates of polymerization, structures, and dynamic properties of the resulting biodynamers. The present study provides a basis for the rational design and synthesis of various types of well-ordered structures and adaptive materials, offering great potential for utilization in the field of biomaterials science.