Synthesis of multifunctional norbornene dicarboximide–phenothiazine monomers bearing pendant fluorophores for controlled ROMP: influence of alkyl chain length on polymerization behavior and photophysical properties

In this study, a new series of norbornene dicarboximide monomers functionalized with phenothiazine derivatives (NDI-COO-RPTZ) as pendant fluorophores was synthesized and characterized by 1D and 2D NMR. These monomers were polymerized via ring-opening metathesis polymerization (ROMP) employing Grubbs first-generation (GI) and second-generation (GII), and Hoveyda Grubbs second-generation (HGII) catalysts. Among them, the GI provided the most effective controlled polymerization behavior affording polymers with molecular weights close to the theoretical values and relatively low dispersities ( Đ ) (1.09–1.25). The NMR analyses showed a high degree of stereoregularity (87–92% trans -olefin). Increasing the length of the N -alkyl side chain prolonged the polymerization time, underscoring the steric influence of the side chain on ROMP kinetics. The synthesized polymers exhibited λ max values of 314–316 nm, in good agreement with the calculated molecular orbital energies, band gaps, and DFT-simulated UV–Vis spectra and display emission in the range of 455–457 nm. Thermal analysis indicated high thermal stability, with a thermal decomposition temperature range of 314–321 °C. SEM images revealed morphological differences attributable to alkyl substituents. Notably, the polymers also exhibited potent antimicrobial activity, with bacterial reduction efficiencies of 93.6% for E. coli , 92.4% for S. aureus , and 83.1% for C. albicans , underscoring their potential as multifunctional optical and antimicrobial materials. In addition, the minimum inhibitory concentration (MIC) was determined to quantify their antimicrobial potency. The polymers exhibited an MIC of 188 µg/mL against S. aureus , compared with 118 µg/mL for Gentamicin under the same conditions, indicating a moderate yet promising antibacterial effect.