Isolation of Living Conjugated Polymer Chains

Living polymerizations currently play a central role in polymer chemistry. However, one feature of these polymerizations is often overlooked, namely, the isolation of living polymer chains. Herein we report the isolation of living π-conjugated polymer chains, synthesized by catalyst-transfer polycondensation. Successful preservation of the nickel complex at polymer chain ends is evidenced by nuclear magnetic resonance spectroscopy, end group analysis, and chain extension experiments. When characterizing living chains by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we discovered a unique photoionization-photodissociation fragmentation process for polymers containing a nickel phosphine end group. Living chains are isolated for several types of conjugated polymers as well as discrete living oligomers. Additionally, we are able to recycle the catalysts from the isolated polymer chains. Catalyst recycling after π-conjugated polymerization has previously been impossible without chain isolation. This strategy not only exhibits general applicability to different monomers but also has far-reaching potential for other catalytic systems.