Semibatch monomer addition as a general method to tune and enhance the mechanics of polymer networks via loop-defect control

Yuwei Gu, Ken Kawamoto, Mingjiang Zhong, Mao Chen, Michael J.A. Hore, Alex M. Jordan, La Shanda T.J. Korley, Bradley D. Olsen, Jeremiah A. Johnson

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


controlling the molecular structure of amorphous cross-linked polymeric materials is a longstanding challenge. Herein, we disclose a general strategy for precise tuning of loop defects in covalent polymer gel networks. This "loop control" is achieved through a simple semibatch monomer addition protocol that can be applied to a broad range of network-forming reactions. By controlling loop defects, we demonstrate that with the same set of material precursors it is possible to tune and in several cases substantially improve network connectivity and mechanical properties (e.g., ∼600% increase in shear storage modulus). We believe that the concept of loop control via continuous reagent addition could find broad application in the synthesis of academically and industrially important cross-linked polymeric materials, such as resins and gels.

Original languageEnglish (US)
Pages (from-to)4875-4880
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number19
StatePublished - May 9 2017

Bibliographical note

Funding Information:
We thank S. L. Buchwald for the syringe pump and W. Zhang for help with FTIR measurements. We thank the National Science Foundation (CHE-1334703) for support of this work. We acknowledge the support of the National Institute of Standards and Technology, US Department of Commerce, in providing the neutron research facilities used in this work. This work made use of the Shared Experimental Facilities supported in part by the Materials Research Science and Engineering Centers Program of the National Science Foundation under Award DMR-1319807.


  • Click chemistry
  • Gels
  • Loops
  • Polymer networks
  • Star polymer


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