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Control of Grafting Density and Distribution in Graft Polymers by Living Ring-Opening Metathesis Copolymerization

Lin, Tzu-Pin and Chang, Alice B. and Chen, Hsiang-Yun and Liberman-Martin, Allegra L. and Bates, Christopher M. and Voegtle, Matthew J. and Bauer, Christina A. and Grubbs, Robert H. (2017) Control of Grafting Density and Distribution in Graft Polymers by Living Ring-Opening Metathesis Copolymerization. Journal of the American Chemical Society, 139 (10). pp. 3896-3903. ISSN 0002-7863. doi:10.1021/jacs.7b00791.

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Control over polymer sequence and architecture is crucial to both understanding structure–property relationships and designing functional materials. In pursuit of these goals, we developed a new synthetic approach that enables facile manipulation of the density and distribution of grafts in polymers via living ring-opening metathesis polymerization (ROMP). Discrete endo,exo-norbornenyl dialkylesters (dimethyl DME, diethyl DEE, di-n-butyl DBE) were strategically designed to copolymerize with a norbornene-functionalized polystyrene (PS), polylactide (PLA), or polydimethylsiloxane (PDMS) macromonomer mediated by the third-generation metathesis catalyst (G3). The small-molecule diesters act as diluents that increase the average distance between grafted side chains, generating polymers with variable grafting density. The grafting density (number of side chains/number of norbornene backbone repeats) could be straightforwardly controlled by the macromonomer/diluent feed ratio. To gain insight into the copolymer sequence and architecture, self-propagation and cross-propagation rate constants were determined according to a terminal copolymerization model. These kinetic analyses suggest that copolymerizing a macromonomer/diluent pair with evenly matched self-propagation rate constants favors randomly distributed side chains. As the disparity between macromonomer and diluent homopolymerization rates increases, the reactivity ratios depart from unity, leading to an increase in gradient tendency. To demonstrate the effectiveness of our method, an array of monodisperse polymers (PLA^x-ran-DME^(1-x))_n bearing variable grafting densities (x = 1.0, 0.75, 0.5, 0.25) and total backbone degrees of polymerization (n = 167, 133, 100, 67, 33) were synthesized. The approach disclosed in this work therefore constitutes a powerful strategy for the synthesis of polymers spanning the linear-to-bottlebrush regimes with controlled grafting density and side chain distribution, molecular attributes that dictate micro- and macroscopic properties.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Lin, Tzu-Pin0000-0001-7041-7213
Chang, Alice B.0000-0001-5036-2681
Chen, Hsiang-Yun0000-0002-6461-1519
Liberman-Martin, Allegra L.0000-0002-8447-905X
Bates, Christopher M.0000-0002-1598-794X
Bauer, Christina A.0000-0002-7687-1676
Grubbs, Robert H.0000-0002-0057-7817
Additional Information:© 2017 American Chemical Society. Received: January 23, 2017; Published: February 21, 2017. This work was supported by the U.S. Department of Energy under award number DE-AR0000683 (ARPA-E program) and by the National Science Foundation under award number CHE-1502616. A.B.C. thanks the U.S. Department of Defense for support through the NDSEG fellowship. A.L.L.-M. thanks the Resnick Sustainability Institute at Caltech for fellowship support. C.M.B. thanks UCSB for funding and the Materials Research Laboratory, a Materials Research Science and Engineering Center (MRSEC) under support from the National Science Foundation (DMR-1121053). C.A.B. thanks the W.M. Keck Foundation for instrumental support. The authors declare no competing financial interest.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Department of Energy (DOE)DE-AR0000683
National Defense Science and Engineering Graduate (NDSEG) FellowshipUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Issue or Number:10
Record Number:CaltechAUTHORS:20170313-100455922
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Official Citation:Control of Grafting Density and Distribution in Graft Polymers by Living Ring-Opening Metathesis Copolymerization Tzu-Pin Lin, Alice B. Chang, Hsiang-Yun Chen, Allegra L. Liberman-Martin, Christopher M. Bates, Matthew J. Voegtle, Christina A. Bauer, and Robert H. Grubbs Journal of the American Chemical Society 2017 139 (10), 3896-3903 DOI: 10.1021/jacs.7b00791
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75055
Deposited By: Ruth Sustaita
Deposited On:13 Mar 2017 17:35
Last Modified:15 Nov 2021 16:30

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