Ladder- and bridge-like polynorbornenes with phosphate linkers: facile one-pot synthesis and excellent properties
A facile one-pot synthesis of a novel bridge-like polymer was accomplished by a sequential ring-opening metathesis polymerization (ROMP) and acyclic diene metathesis (ADMET) polymerization. A telechelic double-stranded poly(norbornene dicarboximide) (PNBI) with two terminal alkenyl groups was first prepared through the third generation Grubbs catalyst-mediated ROMP of a bis(NBI) derivative bearing a phosphate linker, in the presence of a symmetrical multifunctional terminating agent, and was then utilized as a macromonomer in the subsequent ADMET polymerization to yield a bridge-like polymer consisting of a non-conjugated polyolefin backbone and separated double-stranded PNBI. According to the TGA test, the amount of residual carbonaceous mass also increased with the molecular weight of the resultant polymers, indicating excellent thermal stability. The micro-scale combustion calorimetry and limiting oxygen index tests also displayed a superior flame retardant performance.