Synthesis of azo-incorporated copolymers by C1/N2C1 copolymerization under microwave irradiation

Catalyst-free copolymerization of ethyl diazoacetate (EDA) with carbethoxycarbene (CEC) has been achieved through two approaches: microwave irradiation and enzyme-assisted (Novozyme-435) system. The structure of the copolymer was characterized by MALDI-TOF MS (m/z from 2000 to 2450), which suggested that the main chain of the copolymer consisted of CH(COOEt) and NN–CH(COOEt) frameworks. Fourier transform infrared (FTIR) spectrometry, elemental analysis, and Raman spectrometry proved the incorporation of azo group in the copolymer. The results indicated that the CEC radicals were generated under microwave irradiation (with or without Novozyme-435) from EDA. The mechanism study described that the generation speed of CEC radical was faster than its polymerization, and the excess CEC radicals improved the activity of the N2C1 group, thus inducing some EDA molecules as radicals. The two kinds of radicals co-coupled to result in poly(CEC-co-EDA) through the C1/N2C1 copolymerization, but the homopolymerization of CEC radical occurred quicker than its co-coupling with activated EDA.

Graphical abstractCatalyst-free copolymerization of ethyl diazoacetate (EDA) with carbethoxycarbene (CEC) has been achieved through two approaches: microwave irradiation and enzyme-assisted (Novozyme-435) system.Figure optionsDownload full-size imageDownload as PowerPoint slide