Synthesis and characterization of novel diblock copolymers of 5-(N-carbazoyl methyl)bicyclo[2.2.1]hept-2-ene and 5-(phthalimide methyl)bicyclo[2.2.1]hept-2-ene via living ring-opening metathesis polymerization

Ring-opening metathesis polymerization (ROMP) has been performed with {RuCl2(CHPh)[P(C6H11)3]2} catalyst to make low polydispersity block copolymers of 5-(N-carbazoyl methyl)bicyclo[2.2.1]hept-2-ene (CbzNB) and 5-(phthalimide methyl)bicyclo[2.2.1]hept-2-ene (NBMPI). Three diblock copolymers with the CbzNB and NBMPI were made, varying both molecular weight and percent of each block. The hydrogenated diblock copolymers were successfully obtained by using p-toluenesulfonylhydrazide as a reducing agent. The novel diblock copolymers were characterized by means of gel permeation chromatography (GPC) 1H NMR, fluorescence, differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The molecular weight distributions of the diblock copolymers are narrow (Mw/Mn∼1.5). Unhydrogenated diblock copolymers exhibited a strong carbazole fluorescence, with monomer emission occurring in the near-UV at approximately 380 nm and extending into the blue–violet region. Similar results were also observed on hydrogenated diblock copolymers. All diblock copolymers exhibited good solubility in a variety of solvents such as methylene chloride, chloroform, tetrahydrofuran and 1,2-dichlorobenzene; however, there was no remarkable difference between unhydrogenated and hydrogenated diblock copolymers. Two Tg values were observed for the CbzNB segment and the NBMPI segment before and after hydrogenation. Unhydrogenated diblock copolymers exhibited good thermo-oxidative stability, losing 10% mass in the range 369–389°C in air and 400–416°C in nitrogen. However, hydrogenated diblock copolymers showed better thermal stability than unhydrogenated diblock copolymers, and 10% mass loss temperatures were recorded in the range 375–396°C in air and 415–428°C in nitrogen.