Synthesis of well-defined and near narrow-distribution diblock copolymers comprising PMMA and PDMAEMA via oxyanion-initiated polymerization

In this paper, the possibilities offered by oxyanion-initiated polymerization were exploited to tailor well-defined and near narrow-distribution poly[(dimethylamino)ethyl methacrylate]-b-poly(methyl methacrylate) (PDMAEMA-b-PMMA) AB or BA diblock copolymers that were initiated by potassium benzyl alcoholate (BzOK) and controlled by the sequential addition of the alternative monomers. To clarify the living mechanism for MMA and DMAEMA, a series of MMA and DMAEMA homopolymers with near narrow molecular weight distribution were prepared in our laboratory, respectively. If not quenched, the first living moiety could be subsequently used to yield block copolymers BzO-PDMAEMA-b-PMMA with adding the second feed of monomer to the living system. Using reverse succeeding addition of monomers, another benzyloxy-capped diblock copolymer, i.e. BzO-PMMA-b-PDMAEMA was obtained. The thorough characterization of all these diblock copolymers was investigated from 1H NMR measurement. The results indicated that the expected molecular structures have been obtained with a good correlation between original monomer-to-initiator molar ratios. GPC analysis showed that PDMAEMA homopolymer and the above mentioned two block copolymers possessed narrow molecular weight distribution (M¯w/M¯n) in the range of 1.15-1.34, while PMMA homopolymer had a little broad molecular weight distribution of 1.29-1.60. This study shows further evidence that oxyanion-initiated polymerization is a control/'living' process, not only suitable for tertiary amino-substituted methacrylates, but also for methyl methacrylate. The critical micelle concentration (cmc) of the diblock copolymer BzO-PDMAEMA-b-PMMA in aqueous solution was attained by surface tension measurement. The effects of different lengths of two segments and pH values on the behavior of solution were investigated.