1-Naphthylacetic acid (1) was reacted with thionyl chloride and 1-naphthylacetyl chloride (2) was obtained in a quantitative yield. The reaction of this acid chloride (2) with isoeugenol (3) was performed in chloroform and a novel isoeugenol ester derivative (4) as a monomer was obtained in a high yield. The compound (4) was characterized by H-1-NMR, IR, mass, and elemental analyses and then was used for the preparation of a model compound (6) and polymerization reactions. 4-Phenyl-1,2,4-triazoline-3,5-dione (PhTD) (5) was allowed to react with compound (4). The reaction is very fast and gives only one double adduct (6) via Diels-Alder and ene pathways in an excellent yield. The polymerization reactions of the novel monomer (4) with bistriazolinediones [bis-(p-3,5-dioxo-1,2,4-triazolin-4-ylphenyl)methane (7) and 1,6-bis-(3,5-dioxo-1,2,4-triazolin-4-yl)hexane] (8) were carried out in N,N-dimethylacetamide (DMAc) at room temperature. The reactions are exothermic and fast and gave novel heterocyclic polyimides containing a naphthalenic pendant group (9) and (10) via repetitive Diels-Alder-ene polyaddition reactions. Stereochemical analysis of the model compound and fluorimetric studies of the model compound as well as polymers were done conclusively. Excimer formation of the polymers and its effect on fluorescence emission were investigated and some structural characterization and physical properties of these novel heterocyclic polyimides are reported.