The Synthesis Of Four-arm Star PMA, PSt And P(MA-Co-St) By Single Electron Transfer Living Radical Polymerization

In this paper, the star-shaped polymers were synthsized through the"core-fisrt"way by a relatively new polymerization method, which was called Single Electron Transfer Living Radical Polymerization (SET-LRP), and the concrete contents are as follows:1. Through the molecular structure of initiator design, the tetrafunctional initiators including 2,2-dichloromethyl-1,3-dichloropropane (PECl₄) and 2,2-dibromomethyl-1,3-dibromopropane (PEBr₄) were synthesized. The target products were identified by melting point determination, infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1^H NMR).2. The SET-LRP of MA was initiated by PEBr₄ in DMSO with Cu⁰ powder/Me6-TREN as catalytic system at 30℃, the polymers obtained were characterized by 1^H NMR and the results showed that the polymers had perfect chain ends–Br rentention. The value for the apparent rate constant of propagation for the polymerization (k_p^app) was 0.0367h^-1, the molecular weight (M_n^GPC)of the polymer obtained at 36.3% conversion in 16h was 13300 and the molecular weight distribution (M_w/M_n) was about 1.40. The effects of additive such as polar solvent H2O, catalyst and initiator amount on the polymerization were determined.3. The SET-LRP of St was initiated by PEBr₄ in binary mixtures of DMSO and water with Cu⁰ powder/Me6-TREN as catalytic system at 35℃, the polymers obtained were characterized by 1^H NMR and the results showed that the star shaped polymers had perfect chain ends–Br rentention. The value for k_p^app was 0.0264h^-1 and the initiator efficiency (I_eff) was 88%. The effects of the water content in mixtures, reaction temperature, catalyst amount and phase transfer catalyst (PTC) on the polymerization were determined.4. The four-arm star shaped copolymer of MA and St was prepared by SET-LRP at 35℃in DMSO, with using PEBr₄ as initiator and Cu⁰ powder/Me6-TREN as catalytic system. The resulting copolymers were identified by 1^H NMR and the results showed that the copolymers had perfect chain ends–Br tentention. The kinetic plots of polymerization was first order, k_p^app=0.0257h^-1, I_eff=93.2%, the molecular weight distribution of resulting polymers were low (M_w/M_n=1.34-1.45). The effects of water, catalyst amount and PTC on polymerization were determined and the effects of different PTCs on the polymerization were compared.