The reaction of 4-phenyl-1,2,4-triazoline-3,5-dione (PhTD) (2) with trans-3,3-dichloro-1-phenyl-1-propene (4) was investigated at room and reÑux temperatures in methylene chloride solution. Although the reaction is slow, it gives quantitative yield. This reaction leads to the formation of two 2 : 1 adducts via double DielsÈAlder and DielsÈAlder-Ene reactions in a ratio of about 1 : 7. The major product was isolated by means of fractional crystallization as a pure compound and was characterized by infra-red (IR), 1H nuclear magnetic resonance (NMR), 13C NMR, mass spectra and elemental analysis. The structure of the minor product was determined by IR and 1H NMR. These compounds were used as models for the polymerization reactions. The reaction of bistriazolinediones (1,6-bis-(3,5-dioxo-1,2,4-triazoline-4-yl)hexane and bis-(p-3,5-dioxo-1,2,4triazoline-4-ylphenyl)methane) with (4) was carried out in dimethylformamide (DMF). The reactions gave novel polymers via repetitive double DielsÈAlder and DielsÈAlder-Ene polyaddition reactions, with the major component being a DielsÈAlder-Ene structure. These polymers have intrinsic viscosities in a range from 0É08 to 0É18 dl g~1 in DMF. The physical properties and structural characterization of these polymers have been studied and are reported.