Aqueous MADIX/RAFT polymerization of diallyldimethylammonium chloride: Extension to the synthesis of poly(DADMAC)-based double hydrophilic block copolymers

摘要

Macromolecular design by interchange of xanthates/reversible addition fragmentation chain transfer polymerization (MADIX/RAFT) of diallyldimethylammonium chloride (DADMAC) using the hydrophobic O-ethyl-S-(1-methoxycarbonyl) ethyl dithiocarbonate MADIX/RAFT mediating agent, Rhodixan A1, was investigated. Attempts to obtain an efficient control of DADMAC polymerization in a water/ethanol mixture failed because of significant chain transfer to ethanol. The use of a water-soluble Rhodixan A1-terminated acrylamide oligomer as the MADIX/RAFT agent enabled the controlled polymerization of DADMAC in water at 50 °C using the cationic azo initiator V-50. An excellent agreement was found between experimental and theoretical M_n values throughout polymerization and over a broad range of initial concentration of xanthate. Polydispersity indexes (PDIs) at the end of the polymerization were abnormally high for a process showing a linear increase of M_n with monomer conversion (1.8 < PDI < 2.0). This feature was explained by the measurement of a high transfer constant to xanthate (C _x = 18.8 ± 1.6) but a low interchange transfer constant (C_(ex) = 1.5). Nevertheless, poly(acrylamide)-poly(DADMAC) double hydrophilic block copolymers (DHBCs) of controlled M_n and composition could be successfully synthesized for the first time.