Synthesis and characterization of amphiphilic miktoarm star polymers based on sydnone-maleimide double cycloaddition
A new approach to synthesizing amphiphilic miktoarm star polymers (MPEG)2(PCL)2 based on sydnone-maleimide double cycloaddition (SMDC) was investigated using “coupling-onto”, “in–out” and “one-pot” methods. The double 1,3-dipolar cycloadduct could be conveniently obtained by a SMDC reaction between the “arms” maleimide-terminated prepolymers and the “core” N-phenylsyndone. No matter what the molar ratio of sydnone and maleimide groups was, the double cycloaddition products would not be changed. The star polymers synthesized by the “coupling-onto” approach had the narrowest polydispersity, and the “one-pot” approach was the most convenient. The SMDC reaction greatly simplified the synthesis procedure, moreover it had a good control of the structure of miktoarm star polymers. All the polymers’ structures were characterized by 1H NMR, FT-IR and GPC. Their thermal properties were also investigated by DSC. Compared with the linear block polymer, the corresponding miktoarm star polymer showed lower crystallization and melting temperatures and better phase separation.