Abstract
Highly reactive 4‐substituted‐1,2,4‐triazoline‐3,5‐diones (TDs) have been studied extensively as dienophiles, but little work has been done on their role as enophiles and particularly on their use as propagating species in polymerization studies. The copolymerization between bis‐4‐substituted‐1,2,4‐triazoline‐3,5‐diones (bis‐TDs) and styrene has been reported. The purpose of the present work was to synthesize new copolymers derived from a variety of substituted styrenes and bis‐TDs and to study the mechanism and kinetics of this novel polymerization. Three bis‐TDs were prepared: 3,3′‐dimethyl‐4,4′‐bis[3,5‐dioxo‐1,2,4‐triazoline‐4‐yl] biphenyl (8), t‐1,4‐bis[3,5‐dioxo‐1,2,4‐triazoline‐4‐yl] methyl cyclohexane (9), and 4,4′‐bis[3,5‐dioxo‐1,2,4‐triazoline‐4‐yl] phenyl ether (10). Their structures were fully established by spectroscopic studies, elemental analyses, and indirectly, their quantitative ene reactions with 2,3‐dimethyl‐2‐butene. Copolymerization between bis‐TDs and substituted styrenes was carried out in dimethylformamide (DMF), tetrahydrofuran (THF), or dichloroethane (DCE). Polymers formed were characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and viscometry. Molecular weights of polymers range from 5000 to 16,000 in most cases. They were stable up to 250°C and higher. Polymers derived from bis‐TDs and p‐t‐butylstyrene, α‐methylstyrene, p‐nitrostyrene, and p‐acetoxystyrene contained only Diels‐Alder‐ene (DAe) repeating units, whereas those derived from styrene, p‐chlorostyrene, p‐bromostyrene, p‐methylstyrene, p‐methoxystyrene, and 4‐vinylbiphenyl contained both DAe and double Diels‐Alder (dDA) repeating units. A kinetic study of the copolymerization of 4,4′‐bis‐(3,5‐dioxo‐1,2,4‐triazoline‐4‐yl) phenyl ether with α‐methylstyrene, p‐t‐butylstyrene, styrene, p‐chlorostyrene, and p‐nitrostyrene in DCE was carried out; the copolymerization rate constants were 60.9, 49.8, 8.4, 5.5, and 0.8 (1 mol^−1^s), respectively.