Connectivity and Structural Defects in Model Hydrogels: A Combined Proton NMR and Monte Carlo Simulation Study

Lange, Frank de; Schwenke, Konrad; Kurakazu, Manami; Akagi, Yuki; Chung, Ung‐il; Lang, Michael; Sommer, Jens‐Uwe; Sakai, Takamasa; Saalwächter, Kay

doi:10.1021/ma201847v

Cited by 172 publications

(301 citation statements)

References 43 publications

(99 reference statements)

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“…Experimental techniques such as rheology/spectroscopy and multiple-quantum NMR can provide semi-quantitative information related to the loop structure [31][32][33]. Recently, Zhou et al reported 'network disassembly spectrometry' (NDS), which is the first experimental method for directly quantifying primary loops [34,35].…”

mentioning

confidence: 99%

Universal Cyclic Topology in Polymer Networks

et al. 2016

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confidence: 99%

Universal Cyclic Topology in Polymer Networks

et al. 2016

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“…Unlike dangling chains, which can be readily quantified via titration or spectroscopy, there are no known methods for quantification of primary loops. Their prevalence is estimated from pregel measurements or variations between the properties of a given material and theoretical model networks (2,4,(7)(8)(9)(12)(13)(14)(15)(16)(17). These molecular-level mechanical imperfections could critically impact modern applications of polymer networks and gels (18-28), especially those built on an end-linked network architecture (29-33).…”

mentioning

confidence: 99%

Counting primary loops in polymer gels

Zhou¹,

Woo²,

Cok³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

198

223

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Much of our fundamental knowledge related to polymer networks is built on an assumption of ideal end-linked network structure. Real networks invariably possess topological imperfections that negatively affect mechanical properties; modifications of classical network theories have been developed to account for these defects. Despite decades of effort, there are no known experimental protocols for precise quantification of even the simplest topological network imperfections: primary loops. Here we present a simple conceptual framework that enables primary loop quantification in polymeric materials. We apply this framework to measure the fraction of primary loop junctions in trifunctional PEG-based hydrogels. We anticipate that the concepts described here will open new avenues of theoretical and experimental research related to polymer network structure.responsive materials | topology | network disassembly spectrometry | tetrazine T he properties of all known polymer networks, from commodity materials like nylon, rubber, and plastics, to biological tissues such as the extracellular matrix (ECM) and cartilage, are defined by the network's chemical composition and structural topology (1-3). Much of our fundamental knowledge related to polymer materials, e.g., theories of elasticity and gelation, was built more than half a century ago upon an assumption of ideal end-linked network structure (Fig. 1A) (2, 4-7). Real networks invariably possess imperfections such as first-order elastically inactive dangling chains and primary loops (Fig. 1B), and higher-order elastic loop structures and chain entanglements; modifications of classical network theories have been developed to account for these defects (8-11).First-order network imperfections (Fig. 1B) have the most direct negative impact on the mechanical properties of materials. Dangling chains can be minimized if efficient end-linking reactions are used between functional groups present at 1:1 ratio. In contrast, kinetic constraints demand that primary loops exist regardless of functional group conversion (12). Unlike dangling chains, which can be readily quantified via titration or spectroscopy, there are no known methods for quantification of primary loops. Their prevalence is estimated from pregel measurements or variations between the properties of a given material and theoretical model networks (2,4,(7)(8)(9)(12)(13)(14)(15)(16)(17). These molecular-level mechanical imperfections could critically impact modern applications of polymer networks and gels (18-28), especially those built on an end-linked network architecture (29-33).Here we present a simple conceptual framework called network disassembly spectrometry (NDS) that enables facile, simultaneous quantification of the fraction of primary loops and the numbers and structures of dangling chains in end-linked materials via site-selective network disassembly. We apply this framework to degradable PEG hydrogels, which are similar to materials frequently used in tissue engineering applications (29,32).

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“…Future studies could therefore consider realistically generated network samples by using molecular simulations to mimic the crosslinking process [61][62][63]. Ultimately, this and follow-up studies will provide guidance to the design and analysis of novel polymer networks with desirable super tensile properties.…”

Section: Discussionmentioning

confidence: 99%

Mechanical Properties of Tetrapolyethylene and Tetrapoly(ethylene oxide) Diamond Networks via Molecular Dynamics Simulations

Wang

Escobedo

2016

Macromolecules

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The tensile response to uniaxial deformation of polyethylene-based (Tetra-PE) and polyethylene glycol-based (Tetra-PEG) networks of various strand lengths with idealized diamond connectivity have been studied via atomistic molecular dynamics simulations. Tetra-PE and Tetra-PEG diamond networks with the same strand length show comparable maximum extensibility but the Young's moduli and tensile strength of the former are significantly lower than those of the latter, consistent with stronger intersegmental attractions in the amorphous Tetra-PEG networks. The stress-strain curves show that the stress in short-stranded networks increased rapidly and monotonically with strain while for long-stranded networks it increased very little at small strain, in a non-monotonic fashion at intermediate strains, and then very sharply as the limit of extensibility was approached. Spontaneous partial crystallization of a long-stranded Tetra-PE diamond network under supercooling was demonstrated, and the resulting system was used to: (1) Estimate its melting point as the temperature where any crystalline material disappeared abruptly, and (2) show that the presence of crystalline material in the undeformed state leads to higher stress responses upon deformation compared to amorphous samples, a result consistent with experimental observations. The spontaneous crystallization of Tetra-PEG networks at large supercooling was unsuccessful due to the slow motions of the network beads and the prohibitively long crystal nucleation times entailed.iii BIOGRAPHICAL SKETCHThe author, Endian Wang, born in Fujian, China, attended his middle school and high school in He studied and enjoyed sketching and oil painting during middle school and high school, and would like to continue painting in the near future.iv ACKNOWLEDGEMENTS

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Connectivity and Structural Defects in Model Hydrogels: A Combined Proton NMR and Monte Carlo Simulation Study

Cited by 172 publications

References 43 publications

Universal Cyclic Topology in Polymer Networks

Universal Cyclic Topology in Polymer Networks

Counting primary loops in polymer gels

Mechanical Properties of Tetrapolyethylene and Tetrapoly(ethylene oxide) Diamond Networks via Molecular Dynamics Simulations

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