Phosphonated homopolymers and copolymers via ring opening metathesis polymerization: T_g tuning, flame resistance, and photolithography

Phosphonated and epoxy-containing norbornene based monomers were prepared by Diels-Alder reaction. They were then combined with three other commercial cyclic unsaturated monomers to synthesize phosphonated homopolymers and copolymers via ring opening metathesis polymerization (ROMP) using second-generation Grubbs catalyst. Glass transitions of these polymers were tunable in a broad range from -14 to 91 °C by varying the flexibility of comonomer. Interestingly, copolymerization with cyclopentene inhibited the crystallization of polycyclopentene, and instead, led to a copolymer with two T_gs. Paradoxically, results from thermogravimetric analysis (TGA) were not consistent with the followed flame-retarding experiment, implying that the early weight loss from phosphonated moieties did not deleteriously affect the flame-resistant property which actually depended more on the percentage of char residual after thermal degradation. In application studies, the norbornene derivative phosphonated polymer was tested for the first time as flame retarding material, and showed significant self-extinguishing ability. In a second study, photolithography was also successfully performed via thiol-ene "click" chemistry, which allowed the phosphonated polymer a promising negative photoresist.