Synthesis, Characterization, and Thermal Behavior of H-Shaped Copolymers Prepared by Atom Transfer Radical Polymerization

The H-shaped copolymers (PSt) 2 PEG(PSt) 2, which are constructed by attaching two polystyrene branches to both ends of poly(ethylene glycol), were synthesized by atom transfer radical polymerization (ATRP). The synthetic strategy involves the synthesis of 2,2-bis(methylene α-bromopropionate) propionyl chloride, the preparation of 2,2-bis(methylene α-bromopropionate) propionyl terminated poly(ethylene glycol) (BMBP−PEG−BMBP), and then ATRP of styrene at 110 °C using BMBP−PEG−BMBP/CuBr/2,2‘-bipyridine as the initiating system. The structure of the H-shaped copolymers was confirmed by NMR spectroscopy and GPC measurements. The thermal behavior of the H-shaped copolymers was investigated by differential scanning calorimeter. The high molecular weight poly(ethylene glycol) in the H-shaped copolymers shows higher crystalline ability, and the degree of crystallinity, X c, decreases with the decrease of PEG weight fraction in the copolymers.