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Mechanisms of diffusion in associative polymer networks: evidence for chain hopping

Rapp, Peter B. and Omar, Ahmad K. and Silverman, Bradley R. and Wang, Zhen-Gang and Tirrell, David A. (2018) Mechanisms of diffusion in associative polymer networks: evidence for chain hopping. Journal of the American Chemical Society, 140 (43). pp. 14185-14194. ISSN 0002-7863.

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Networks assembled by reversible association of telechelic polymers constitute a common class of soft materials. Various mechanisms of chain migration in associative networks have been proposed; yet there remains little quantitative experimental data to discriminate among them. Proposed mechanisms for chain migration include multichain aggregate diffusion as well as single-chain mechanisms such as “walking” and “hopping”, wherein diffusion is achieved by either partial (“walking”) or complete (“hopping”) disengagement of the associated chain segments. Here, we provide evidence that hopping can dominate the effective diffusion of chains in associative networks due to a strong entropic penalty for bridge formation imposed by local network structure; chains become conformationally restricted upon association with two or more spatially separated binding sites. This restriction decreases the effective binding strength of chains with multiple associative domains, thereby increasing the probability that a chain will hop. For telechelic chains this manifests as binding asymmetry, wherein the first association is effectively stronger than the second. We derive a simple thermodynamic model that predicts the fraction of chains that are free to hop as a function of tunable molecular and network properties. A large set of self-diffusivity measurements on a series of model associative polymers finds good agreement with this model.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Rapp, Peter B.0000-0002-9586-2126
Omar, Ahmad K.0000-0002-6404-7612
Silverman, Bradley R.0000-0002-9256-8941
Wang, Zhen-Gang0000-0002-3361-6114
Tirrell, David A.0000-0003-3175-4596
Additional Information:© 2018 American Chemical Society. Received: July 25, 2018; Published: October 1, 2018. We thank Andres Collazo of the Caltech Beckman Imaging Facility for expert assistance with acquisition of FRAP data. This work was supported by grant number DMR-1506483 from the Biomaterials Program of the U.S. National Science Foundation. A.K.O. acknowledges support from the National Science Foundation Graduate Research Fellowship under grant no. DGE-1144469 and an HHMI Gilliam Fellowship. B.R.S. acknowledges support from NIH predoctoral training grant 1T32GM112592 and from the Rosen Center for Bioengineering. P.B.R. and A.K.O. contributed equally to this work. The authors declare no competing financial interest.
Group:Rosen Bioengineering Center
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
NIH Predoctoral Fellowship1T32GM112592
Donna and Benjamin M. Rosen Bioengineering CenterUNSPECIFIED
Subject Keywords:diffusion, mechanism, hopping, entropy, binding, hydrogel, FRAP
Issue or Number:43
Record Number:CaltechAUTHORS:20181001-131358075
Persistent URL:
Official Citation:Mechanisms of Diffusion in Associative Polymer Networks: Evidence for Chain Hopping. Peter B. Rapp, Ahmad K. Omar, Bradley R. Silverman, Zhen-Gang Wang, and David A. Tirrell. Journal of the American Chemical Society 2018 140 (43), 14185-14194. DOI: 10.1021/jacs.8b07908
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90073
Deposited By: George Porter
Deposited On:03 Oct 2018 17:33
Last Modified:03 Oct 2019 20:21

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