Preparation, hydrogen bonding and properties of polyurethane elastomers with 1,2,3‐triazole units by click chemistry

Two kinds of diols containing 1,2,3‐triazole units were synthesized through the azide‐alkyne cycloaddition reaction between propargyl alcohol and 1,4‐diazidobutane. One of the diols, (butane‐1,4/1,5‐diylbis[1H‐1,2,3‐triazole‐1,4/1,5‐diyl])dimethanol (BDTDO‐1), containing 1,4/1,5‐disubstituted 1,2,3‐triazole regioisomers, was directly prepared under thermal condition without Cu(I) catalyst. The other diol, (butane‐1,4‐diylbis[1H‐1,2,3‐triazole‐1,4‐diyl])dimethanol (BDTDO‐2), containing 1,4‐disubstituted 1,2,3‐triazoles, was prepared by Cu(I) catalyzed click chemistry. Then, two kinds of 1,2,3‐triazole modified polyurethane elastomers (PUEs) were prepared from the reaction of 4,4′‐methylenebis(phenyl isocyanate) and poly(tetramethylene ether) glycol, with BDTDO‐1 or BDTDO‐2 as the chain extender (CE). It was found that the introduction of 1,2,3‐triazoles and their substitution positions had significant influences on the hydrogen bonding, thermal and mechanical properties of PUEs. Compared with the PUE prepared from 1,4‐butanediol as the CE, the PUE containing symmetric 1,4‐disubstituted 1,2,3‐triazoles units in the main chains shows higher values of hydrogen bonding, physical crosslinking density, Young's modulus, tensile strength and melting temperature, while lower glass transition temperature, resulting from the rigid structure and the ability to form more hydrogen bonds. However, the introduction of asymmetric 1,4/1,5‐disubstituted 1,2,3‐triazole moieties decreases the values of hydrogen bonding, thermal and mechanical properties of PUE appreciably due to the destruction of the ordered structure of the hard segments.