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Published December 14, 2011 | Supplemental Material
Journal Article Open

EPR Study of Spin Labeled Brush Polymers in Organic Solvents


Spin-labeled polylactide brush polymers were synthesized via ring-opening metathesis polymerization (ROMP), and nitroxide radicals were incorporated at three different locations of brush polymers: the end and the middle of the backbone, and the end of the side chains (periphery). Electron paramagnetic resonance (EPR) was used to quantitatively probe the macromolecular structure of brush polymers in dilute solutions. The peripheral spin-labels showed significantly higher mobility than the backbone labels, and in dimethylsulfoxide (DMSO), the backbone end labels were shown to be more mobile than the middle labels. Reduction of the nitroxide labels by a polymeric reductant revealed location-dependent reactivity of the nitroxide labels: peripheral nitroxides were much more reactive than the backbone nitroxides. In contrast, almost no difference was observed when a small molecule reductant was used. These results reveal that the dense side chains of brush polymers significantly reduce the interaction of the backbone region with external macromolecules, but allow free diffusion of small molecules.

Additional Information

© 2011 American Chemical Society. Publication Date (Web): October 24, 2011. Received: September 9, 2011. We gratefully thank Dr. Xuegong Lei for help with initial EPR experiments. This work was supported by the Department of Energy (DE-FG02-05ER46218) and by the NSF Center for the Science and Engineering of Materials at the California Institute of Technology.

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Supplemental Material - ja2085349_si_001.pdf


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