Living ring-opening metathesis polymerization of norbornenes bay-functionalized perylene diimides

Ring-opening metathesis polymerization (ROMP)-derived poly(oxanorbornene imide)s bearing bay-linked mono-alkoxy-M1 and 1,7-di-alkoxy M2 functionalized perylene diimides (PDIs) were synthesized using Grubb's third (G3) and Hoveyda-Grubbs second generation (HG2) ruthenium-alkylidene metathesis initiators. The mono-alkoxy-derived PDI-based non-ladderphane polymer polyM1 displayed 67% to 77% of the trans olefin content in the polymer chain depending on the initiator used for the polymerization. When using the symmetrical 1,7-di-alkoxy-derived PDI-based polymer polyM2 having the ladderphane type-structure, this displayed a significant amount of cis and trans olefin contents in the polymer chains, irrespective of the type of initiators used for the polymerization. ROMP of both monomers M1 and M2 proceeded in a well-controlled manner with a linear dependence of molecular weight on the monomer/initiator ratio using G3 as initiator. Optical properties of the ladderphane-based polyM2 and non-ladderphane-based polyM1 were characterized in both solution and the film state. X-ray diffraction (XRD) analysis for all the polymers showed significant pi-stacking in the thin film state with ordered molecular packing and closer values of d-spacing for both polyM1 and polyM2. Film morphology examined by AFM elucidated homogenous smooth polymer surface for both polymers in general, but with some irregularities observed for polyM1. In addition, CV analysis revealed both polymers could be good candidates as electron-accepting materials, with excellent film-forming ability, and thermal stability.

Automated summary

Polymerization of ROMP-derived polyM1 and polyM2 shows differences in the content of trans olefins and the optical properties in solution and film state. Both polymers exhibit excellent characteristics as electron-accepting materials with good film-forming ability and thermal stability, despite some differences in film morphology observed by AFM analysis.