Living ROMP of Poly(m,p-phenylenevinylene) and Functionalized Norbornene-Dicarboximides Copolymers: Guided Synthesis Toward Enhanced Optoelectronic and Thermal Properties with DFT Insights

Abstract

A series of functionalized copolymers is synthesized via ring-opening metathesis polymerization (ROMP). Dioctyloxy-substituted [2.2]metaparacyclophane-1,9-diene (DO-mp-CPDE) (M1), was synthesized and fully characterized by IR, 1D-NMR, and 2D-NMR. A novel fully conjugated polymer, poly(m,p-phenylenevinylene), along with rod–coil copolymers (P2-P5) incorporating DO-mp-CPDE and non-conjugated units Norbornene Dicarboximides (NDI), was synthesized utilizing ROMP with second-generation Grubbs catalyst (G2). Kinetics studies examined using GPC confirmed controlled living polymerization in homopolymer and block designs, evidenced by PDI 1.10–1.17 and a close agreement between experimental and calculated Mn values. In contrast, random copolymers exhibited broader distributions due to ring strain mismatch. Optical measurements revealed tunable band gaps, E_g^op 2.53–2.56 eV, and electrochemical gaps, E_g^elc 2.01–2.37 eV, with enhanced conjugation in the homopolymer leading to narrower gaps. Morphological investigations using SEM showed distinct self-assembly behaviours influenced by the polymer chain and the micellization protocol, which explains the enhancement in the optical properties of these polymers with E_g^op 2.27–2.41 eV. TGA analysis demonstrated high thermal stability across all polymers, with a range of around 368.2–394.6 °C. DFT and TD-DFT calculations confirmed that the effective conjugation length has been gained in all polymers. These findings highlight the versatility of ROMP in creating conjugated polymers with tunable optoelectronic performance and improved thermal stability, making them promising for flexible electronics applications.