Plasmonic polymers present an interesting concept that builds on the analogy between molecular polymers and linear chains of strongly interacting metal nanoparticles. Ensemble-averaged optical properties of plasmonic polymers are strongly influenced by their structure. In the present work, we formed plasmonic polymers using solution-based assembly of gold nanorods (NRs) end-tethered with photoactive macromolecular tethers. By using post-assembly ligand photocrosslinking, we established a method to arrest growth of NR chains after a particular self-assembly time, and in this manner, using kinetics of step-growth polymerization, we achieved control over the average degree of polymerization of plasmonic polymers. Photocrosslinking of ligands also enabled control of the inter-nanorod distance and resulted in the increased rigidity of NR chains. These results, along with a higher structural integrity of NR chains, can be utilized in plasmonic nanostructure engineering, and facilitate advanced applications of plasmonic polymers in sensing and optoelectronics.