Nitroxide-mediated polymerization to form symmetrical ABA triblock copolymers from a bidirectional alkoxyamine initiator

Bidirectional alkoxyamine 2 was synthesized and used as the initiator in the polymerization of styrene (S), n-butyl acrylate (nBA), t-butyl acrylate (tBA), isoprene (I), and dimethylacrylamide (DMA). A variety of symmetrical ABA triblock copolymers were prepared, ranging in size from 5 to 59 kDa. Kinetics studies and gel permeation chromatography (GPC) confirmed the “living” nature of these polymerizations. Trifluoroacetic acid was used to convert the PtBA blocks of these polymers into poly(acrylic acid) (PAA) blocks, forming ABA amphiphilic triblock copolymers. AFM images of PAA-b-PnBA-b-PAA and PAA-b-PS-b-PAA triblock copolymers ionized by the addition of 2,2′-(ethylenedioxy)bis(ethylamine) show evidence of self-assembly.