The incorporation of pendant iptycene units into polyesters creates a novel polymer-chain contour resembling \"mol. barbed wire.\". These types of units contain a unique structural property called the internal mol.-free vol. (IMFV) and have been shown to induce steric interactions between polymer chains through the minimization of the IMFV. This process creates a sterically interconnected polymer-chain network with high ductility because of two new mechanisms: mol. threading and mol. interlocking. The ability for these mechanisms to enhance the mech. properties of polyesters is robust across concn. and processing conditions. The size, shape, and concn. of these pendant units affect the mech. behavior, and results indicate that the larger units do not necessarily produce superior tensile properties. However, the mol.-barbed-wire architecture consistently produces enhanced mech. properties compared to the ref. polyester. The particular stress-strain response can be tailored by minute changes to the periphery of the iptycene unit. [on SciFinder(R)]