Synthesis and Enhanced Photofluorescence of Pyrazoline‐Ester Copolymers from Bisdiazoacetates and Diacrylates

Abstract

Photofluorescent pyrazoline‐ester copolymer is synthesized from bisdiazoacetate and diacrylate through two tandem 1,3‐dipolar cycloadditions at room temperature. The first 1,3‐dipolar cycloaddition takes place between bisdiazoacetate and diacrylate, and produces the diazoacetate and acrylate‐terminated pyrazoline monomer that undergoes second 1,3‐dipolar cycloaddition further to form pyrazoline‐ester copolymer in excellent yield (up to 90%) with number‐average molecular weights (Mn) in the range of 6100–17900 g mol−1. The optimized bisdiazo and dialkene are 1,4‐cyclohexanedimethyl bisdiazoacetate and 1,6‐hexanediol diacrylate, from which the pyrazoline‐ester copolymer with Mn 17900 g mol−1 is obtained in 97% yield and the maximum emission intensity (I/N) is enhanced to be as high as 19 × 104 a.u.. The pyrazoline‐ester copolymers are down/upconversion fluorescence materials, which emit 320–330 nm UV light through the excitation of both mid‐UV and visible light, and could find wide application in the optical field.