Synthesis of styrene-norbornene diblock copolymers via ring-opening metathesis polymerization and nitroxide-mediated radical polymerization

Diblock copolymers containing polynorbornene (PNB) and polystyrene (PS) were synthesized by ring-opening metathesis polymerization (ROMP) and nitroxide-mediated radical polymerization (NMRP) approach. PNB containing nitroxide free radical was prepared by ROMP in presence of Grubbs 2nd generation catalyst and served as a macro-initiator for NMRP of styrene to achieve the targeting diblock copolymers. The effects of the chain transfer agent (CTA) concentration, catalyst amount, reaction time and reaction temperature on the synthesis of macro-initiator as well as the effects of mole ratio of monomer to macro-initiator and reaction time on the synthesis of diblock copolymers were studied. As a result, the diblock copolymers with M-n ranging from 5 kDa to 10 kDa and PDI ranging from 1.5 to 1.8 were obtained successfully. The desired diblock copolymers have broad applications in polymer electrolytes, nanoporous membranes and many other fields.