Abstract
Interpenetrating polymer networks (IPNs), consisting of two or more chemically independent networks, represent a significant type of polymer combination in modern industry, especially in automotive and medical devices. Diverse synthesis techniques and plentiful raw materials highlight IPNs in providing facile modifications of properties to meet specific needs. We here report on an initiator-free synthesis of interpenetrating polymer networks via Bergman cyclization (BC), acting as a triggered source for generating the second network via its reactive enediyne (EDY) moiety, embedded into the first network. (Z)-oct-4-ene-2,6-diyne-1,8-diol (diol-EDY) is targeted as the precursor of the second network, swollen into the first polyurethane network (PU), followed by radical polymerization. The formation of the IPN was monitored via electron paramagnetic resonance (EPR) spectroscopy, infrared-spectroscopy (FT-IR), and thermal methods (DSC), proving the activation of the EDY-moiety and its subsequent crosslinking to form the second network. Stress − strain characterization and cyclic stress − strain investigations, together with TGA and DTG analysis, illustrate improved mechanical properties and thermal stability of the formed IPN compared to the initial PU-network. The method presented here is a novel and broadly applicable approach to generate IPNs, triggered by the EDY-activation via Bergman cyclization.