Volume 35, Issue 2 p. 133-140
Communication

Exploring Quality in Gradient Copolymers

Andrea M. Elsen,

Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA, 15213 USA

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Yuanchao Li,

Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA

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Qiaoxi Li,

Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA

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Sergei S. Sheiko,

Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA

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Krzysztof Matyjaszewski,

Corresponding Author

Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA, 15213 USA

Fax: +14122686897, E-mail: km3b@andrew.cmu.eduSearch for more papers by this author
First published: 22 October 2013
Citations: 26

Abstract

Quality of gradient copolymers is evaluated by atomic force microscopy (AFM) and correlated with molecular weight distribution (MWD) values. ARGET ATRP is employed with decreasing levels of catalyst concentrations to generate copolymers with increasing urn:x-wiley:10221336:marc201300654:equation:marc201300654-math-0001/urn:x-wiley:10221336:marc201300654:equation:marc201300654-math-0002 values. The copolymers are transformed into molecular bottlebrushes to enable imaging and analysis of individual molecules by AFM. The average height (cross-sectional) profile of all bottlebrushes agrees with the instantaneous composition (ICHEMA-TMS) of the analogous copolymer backbone, as determined by 1H NMR. The copolymer synthesized with 500 ppm of catalyst exhibits more narrow distributions of both brush height and backbone length when analyzed as a bottlebrush by AFM. Correspondingly, the copolymers synthesized with lower catalyst concentrations yield bottlebrushes with broader height and length distribution. These results establish MWD values as an excellent trait to assess quality within gradient copolymers.

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