Synthesis of Star-like Random Copolymers from Resorcinarene-Based Octa-Functional Alkoxyamine Initiator via Nitroxide Mediated Free Radical Polymerization

摘要

An octa-functional alkoxyamine initiator,with the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) free radical,was synthesized based on resorcinarene,with its efficiency to initiate the nitroxide-mediated free radical copolymerization of styrene and methyl methacrylate (MMA) described.A difunctional analogue of this initiator was also synthesized,using resorcinol as the core molecule.The structures of the resulting initiators were confirmed by homolysis studies based on electron spin resonance spectroscopy and molecular modeling.The polymerization behavior and characteristics of the polymers obtained using these two initiators were also compared.Well-defined star-shaped and linear random copolymers,with low polydispersities and controlled molecular weights,were prepared.The efficiencies of these initiators towards copolymerization,as well as the parameters permitting the formation of well-defined polymers,were also investigated.The reactivity ratios were r_a=0.42 (a=styrene) and r_b=0.33 (b=MMA) for the octa-functional initiator system and r_a=0.45 and r_b=0.39 for the difunctional initiator system.