Synthesis and characterization of poly[(1-vinyl-1,2,4-triazole)-co -(monomer with carboxylic acid group(s))] and determination of monomer reactivity ratios: I. Acrylic acid

Abstract

Copolymers of 1-vinyl-1,2,4-triazole (VTAz) and acrylic acid (AA) having different mole ratios were synthesized using free radical-initiated solution polymerization in dimethylformamide at 70 °C with α,α′-azobisisobutyronitrile as initiator in nitrogen atmosphere. The compositions of the synthesized copolymers for a wide range of monomer feeds were determined using Fourier transform infrared (FTIR) spectroscopy through recorded absorption bands for VTAz (1510 cm−1, CN (triazole ring) stretching mode) and AA (1710 cm−1, CO stretching mode) units. The structures of the copolymers were characterized using FTIR and 1H NMR spectroscopy. The copolymer compositions were also determined from 1H NMR analysis following proton signals of carboxyl group at 11.8–12.5 ppm of AA and of triazole ring at 7.5–8.1 ppm of VTAz. Monomer reactivity ratios for the VTAz-AA pair were estimated using linear methods, i.e. Fineman–Ross (FR) and Kelen–Tüdös (KT). From FTIR evaluation, monomer reactivity ratios were calculated as r1 = 0.404 and r2 = 1.496 using the FR method and r1 = 0.418 and r2 = 1.559 using the KT method. These values were found to be very close to those obtained from NMR evaluation. The two cases r1r2 < 1 and r1 < r2 indicated the random distribution of the monomers in the final copolymers and the presence of a greater amount of AA units in the copolymer than in the feed, respectively. The observed relatively high activity of complexed growing radical-AA• … VTAz was explained by the effect of complex formation between carbonyl groups and triazole fragments in chain growth reactions. Thermal behaviours of copolymers with various compositions were investigated using thermogravimetric and differential scanning calorimetric analyses. It was observed that thermal stabilities and glass transition temperatures of the copolymers increased resulting from complex formation between acid and triazole units. © 2012 Society of Chemical Industry