SYNTHESIS AND CHARACTERIZATION OF FOUR-ARMED BLOCK POLY(STYRENE-b-p-NITROPHENYL METHACRYLATE)PREPARED BY THE ATRP METHOD*

 A novel tetrafunctional initiator, C CH₂O (CH₂)₃ OOCCH(Br)CH₃]₄ (1), was synthesized through the reaction oftetraol with α-bromopropionyl chloride, and then was used as initiator of atom transfer radical polymerization (ATRP) in thepreparation of 4-armed polystyrene (PSt) with narrow polydispersity. The structure, molecular weight and molecular weightdistribution (MWD) of each arm were studied by ¹H-NMR and GPC data of hydrolyzed products of the 4-armed PSt.The ATRP of St using 1/CuBr/bpy as initiator system is of "living" character based on the following evidence:narrow MWD,constant concentration of chain radical during the polymerization,control of molecular weight by the molar ratio of monomer consumed to 1.The 4-armed poly(St-b-P-nitrophenyl methacrylate)poly(St-b-NPMA)] was prepared by the ATRP of NPMA using 4-armed PSt with terminal bromine as the initiator,and characterized by FT-IR,¹H-NMR spectra and GPC curves.The micelles with PSt as core,and PNPMA as shell were formed by dropping DMSO into a solution of 4-armed poly(St-b-NPMA) in DMF,as proved by laser light scatter(LLS) method.