The polyethylene glycol xanthate-mediated synthesis of block copolymers via novel MADIX agents containing azo initiator: Effect of PEG chain length on molecular properties

Abstract

Novel macro-xanthate agents containing azo initiator and polyethylene glycol (PEG) were synthesized to prepare block copolymers via macromolecular design by an interchange of xanthate (MADIX) polymerization. In this system, the multifunctional agents were used as both macromolecular chain transfer agents and free radical sources. Polystyrene–polyethylene glycol–polystyrene (PS-PEG-PS) copolymers were prepared easily with molecular weight (Mn) from 23,000 to 43,000 g/mol by MADIX copolymerization of styrene using PEG-N\u2009=\u2009N-PEG (Mn, PEG\u2009=\u2009600, 1000, 1500, and 3000 g/mol) as the macro-MADIX agents. In this process, the molar mass (Mn) increased over time for a controlled MADIX polymerization process, but the polydispersity varied slightly. The controlled polymerizations showed typical living properties, and polymers having low polydispersity (below Đ\u2009<\u20091.4) were obtained with well-defined macromolecular structures. As a result, the macro-MADIX agents and the azo-initiator macromolecules were performed successful formation of the block copolymers. The obtained block copolymers were characterized by gel permeation chromatography, differential scanning calorimetry, Fourier transform infrared spectroscopy, and hydrogen nuclear magnetic resonance (1H NMR) spectroscopy.