Chemical Reactions on Polymers. II. Modification of Diene Polymers with Triazolinediones via the Ene Reaction

A wide variety of polymers and copolymers of 1,3-dienes have been modified at low temperatures via the ene reaction with 4-substituted l,2,4-triazoline-3,5-diones. The resulting modified polymers were characterized via infrared spectroscopy, nuclear magnetic resonance, intrinsic viscosity, gel-permeation chromatography, differential scanning calorimetry, solubility tests, and tensile measurements. Physical properties measurements support the postulate that the highly polar pendant urazole groups contribute inter molecular and intramolecular hydrogen-bonding interactions and thus impart to the modified polymers thermoplastic elastomer properties. Changes in the solubility character, thermal behavior, and tensile properties of the modified polymers are in accord with this postulate. Since the association between molecules is physical in nature, the modified polymers remain soluble in appropriate solvents. They also show dramatic decreases in molecular size; for example, the average molecular size of polymers at 1% modification is about one tenth that of the unmodified polymer due to intramolecular interactions, a size reduction of the same order of magnitude as that of chemically crosslinked polymers. Poly-1,2-butadiene, when modified to the extent of 5%, gave values for elongation to break, Young's modulus, and tensile strength twice those for the parent polymer, while tensile recoveries were > 90%.