Synthesis of Dense 1,2,3-Triazole Polymers Soluble in Common Organic Solvents

Aiming at synthesis of dense 1,2,3-triazole polymers soluble in common organic solvents, a new 3-azido-1-propyne derivative, i.e., t-butyl 4-azido-5-hexynoate (tBuAH), was synthesized and polymerized by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) and Huisgen cycloaddition (HC). CuAAC polymerization produced poly(tBuAH) composed of 1,4-disubstituted 1,2,3-triazole units (1,4-units), whereas HC polymerization gave poly(tBuAH) composed of 1,4- and 1,5-disubstituted 1,2,3-triazole units (1,4- and 1,5-units). In HC polymerization, the fraction of 1,4-unit (f(1,4)) decreased with the permittivity of solvent used. Differential scanning calorimetry data indicated that the melting point of poly(tBuAH) increased from 61 to 89 degrees C with increasing f(1,4) from 0.38 to 1.0, indicative of higher crystallinity of poly(tBuAH) composed of 1,4-unit. Preliminary steady-state fluorescence study indicated that all the poly(tBuAH) samples of different f(1,4) emitted weak but significant fluorescence in DMF. The maximum of fluorescence band shifted from ca. 350 to ca. 450 nm with varying the excitation wavelength from 300 to 400 nm.

Automated summary

Through copper(I)-catalyzed and Huisgen cycloaddition reactions, 1,2,3-triazole polymers with different substituents were successfully synthesized. The crystalline properties of the polymers were influenced by the permittivity of the solvent and the type of substituents used. Additionally, the polymers exhibited fluorescence behavior in DMF, with the fluorescence peak shifting based on the excitation wavelength.