We report the modification of diaryl disulphide-containing dynamic covalent polyesters (DADS-PEs) via an iodine-catalysed addition reaction with styrene derivatives that proceeds in an insertion-like manner. The simple procedure of these reactions enabled facile control of the primary structure and physical properties of DADS-PEs by using various styrene derivatives with several polar substituents, flexible oligomeric chains, and two vinyl functionalities that work as a cross-linker. The addition reactions were also found to be an efficient method for “fixing” the polymer structure via conversion of dynamic diaryl disulphide bonds, which are susceptible to bond exchange reactions under photo-irradiation.