Amphoteric polymers have been studied for various applications such as separation of low molecular weight organic molecules from inorganic salt mixtures, selective ion transport, drug delivery through membranes of biological interest, separation of ionic drugs and proteins, and separation of alcohol and water. Typical amphoteric polymers consist of weak base and weak acid groups. In present study, the copolymerization of 5-vinyltetrazole (VT) and diisopropyl-p-vinylbenzyl phosphate (DIPVBP) via free radical polymerization is studied. The reactivity ratio of VT and DIPVBP, which is calculated from Kelen-Tudos plot, is 0.251 and 0.345, respectively. The amphoteric copolymer of VT and diisopropyl-p-vinylbenzyl phosphonic acid (poly(VT-co-VBPA)) is obtained from hydrolysis of the copolymer of VT and DIPVBP (poly(VT-co-DIPVBP)). Poly(VT-co-VBPA) is thermally stable under 190 degrees C. The anhydrous proton conductivity of amphoteric poly(VT-co-VBPA) can reach 1.54 x 10(-4) S cm(-1) at 170 degrees C with an activation energy of 114.7 kJ mol(-1). (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3486-3493