Various diene polymers have been modified at room temperature via the ene reaction with 4-substituted-1,2,4-triazoline-3,5-diones. The resulting modified polymers were characterized by means of IR spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, and solubility tests. Physical properties measurements support the assumption that the highly-polar pendant urazole groups play an important role in both inter-molecular and intramolecular hydrogen bonding interaction, and accordingly give thermoplastic properties to the modified polymers. Changes in the thermal analysis and solubility character of the modified polymers agree fairly well with this assumption. The modified polymers remain soluble in suitable solvents because of the physical nature of the association between molecules.