Synthesis of a branched star copolymer by aqueous SET-LRP and its thermo-stimuli response

Abstract

Thermally responsive star-shaped polyacrylamides have been efficiently synthesized by copolymerization of acrylamide (AM) with AM-based macromonomer (MPAD) by single-electron-transfer living radical polymerization. Copolymerizations using Gly-Br₃ as an initiator were catalyzed by full in situ disproportionation of CuBr/Me₆TREN to Cu(0) powder and CuBr₂ and were performed in H₂O at 25 °C. The polymerization proceeded smoothly, and the time dependence of ln([M]₀/[M]) was linear, implying that the copolymerization was a living polymerization. The polymer products were characterized by FTIR spectroscopy, ¹H NMR spectrometry, and atomic force microscopy. The responsiveness of the water-soluble star-shaped copolymers were studied by turbidity measurements, dynamic light scattering, and transmission electron microscopy. The lower critical solution temperature of a random copolymer can be tuned by changing the feed ratio of MPAD in its synthesis. The phase transition temperature of the copolymer decreased with increasing MPAD content. At a feed ratio of MPAD of 10%, the copolymer obtained exhibited a strong thermal response and could form vesicles.

Graphical Abstract

Keywords:

• Single-electron transfer living radical polymerization
• macromonomer
• acrylamide
• copolymerization
• thermo-stimuli response

Acknowledgment

We thank International Science Editing (http://www.internationalscienceediting.com) for editing this manuscript.

Conflict of interest

The authors declare that they have no competing interests.

Additional information

Funding

The present study was funded by National Nature Science Foundation of China (project no. 51474068), National Nature Science Foundation of China (project no. 51834005) and Cultivation fund of Northeast Petroleum University (xm123442).