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

• Main Authors: Shota Yamasaki, Yuri Kamon, Linlin Xu, Akihito Hashidzume
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Polymers
• Subjects: Huisgen cycloaddition polymerization; copper(I)-catalyzed azide–alkyne cycloaddition polymerization; <i>t</i>-butyl 3-azide-6-hexynoate; 1,2,3-triazole
• Online Access: https://www.mdpi.com/2073-4360/13/10/1627

Aiming at synthesis of dense 1,2,3-triazole polymers soluble in common organic solvents, a new 3-azido-1-propyne derivative, i.e., <i>t</i>-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 (<i>f</i>_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 °C with increasing <i>f</i>_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 <i>f</i>_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.