Scale-Dependent Stiffness and Internal Tension of a Model Brush Polymer

Berezney, John P.; Marciel, Amanda B.; Schroeder, Charles M.; Saleh, Omar A.

doi:10.1103/physrevlett.119.127801

Cited by 12 publications

(21 citation statements)

References 31 publications

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“…The general methods developed by Schroeder and coworkers for synthesizing comb-shaped polymers based on double stranded DNA [230] were recently extended to synthesize bottlebrush polymers based on ssDNA [231]. The bottlebrush polymers consist of a ssDNA main chain backbone with poly(ethylene glycol) (PEG) side chains.…”

Section: Bottlebrush Polymersmentioning

confidence: 99%

“…These experiments are currently being extended to non-dilute solutions, which will be essential in comparing to molecular constitutive equations for comb polymer architectures that have so far been compared only to bulk rheological experiments [243]. Moreover, recent single molecule experiments on bottlebrush polymers have revealed the importance of an internal scale-dependent tension that impacts chain elasticity [231], which fundamentally changes the force-extension behavior away from linear unbranched polymers. This work follows single molecule studies probing the role of excluded volume interactions on generating a non-linear low-force elasticity for linear polymers [38], which subsequently inspired the development of several new force-extension relations for polymer chains that depend on solvent quality [63,67].…”

Section: Bottlebrush Polymersmentioning

confidence: 99%

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Single polymer dynamics for molecular rheology

Schroeder

2018

Journal of Rheology

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113

127

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Single polymer dynamics offers a powerful approach to study molecular-level interactions and dynamic microstructure in materials. Direct visualization of single chain dynamics has uncovered new ideas regarding the rheology and non-equilibrium dynamics of macromolecules, including the importance of molecular individualism, dynamic heterogeneity, and molecular sub-populations that govern macroscale behavior. In recent years, the field of single polymer dynamics has been extended to increasingly complex materials, including architecturally complex polymers such as combs, bottlebrushes, and ring polymers and entangled solutions of long chain polymers in flow. Single molecule visualization, complemented by modeling and simulation techniques such asBrownian dynamics and Monte Carlo methods, allow for unparalleled access to the molecular-scale dynamics of polymeric materials. In this review, recent progress in the field of single polymer dynamics is examined by highlighting major developments and new physics to emerge from these techniques. The molecular properties of DNA as a model polymer are examined, including the role of flexibility, excluded volume interactions, and hydrodynamic interactions in governing behavior. Recent developments in studying polymer dynamics in time-dependent flows, new chemistries and new molecular topologies, and the role of intermolecular interactions in concentrated solutions are considered. Moreover, cutting-edge methods in simulation techniques are further reviewed as an ideal complementary method to single polymer experiments. Future work aimed at extending the field of single polymer dynamics to new materials promises to uncover original and unexpected information regarding the flow dynamics of polymeric systems.

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Section: Bottlebrush Polymersmentioning

confidence: 99%

Section: Bottlebrush Polymersmentioning

confidence: 99%

Single polymer dynamics for molecular rheology

Schroeder

2018

Journal of Rheology

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113

127

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“…This result is attributed to the extrinsic stiffness of bottlebrushes with the side-chain steric effect diminished at high forces. Further experimental evidence of scale-dependent stiffness comes from magnetic tweezer force spectroscopy by Saleh and co-workers. , For bottlebrushes of ssDNA backbones with poly(ethylene glycol) side chains and hyaluronan backbones with aggrecan side chains, a single value of based on the WLC formula was insufficient to capture the force-extension behavior. Rather, following prior work on polyelectrolyte stretching, they argue that the side chains induce an internal tension on the bottlebrush backbone that needs to be accounted for within the WLC formula; stiffness is again drastically reduced as the bottlebrush molecules is stretched. , …”

Section: Introductionmentioning

confidence: 99%

Two Stretching Regimes in the Elasticity of Bottlebrush Polymers

Dutta

Sing

2020

Macromolecules

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The elasticity of highly branched polymers, known as bottlebrush polymers, is integral to understanding their physical properties in a wide variety of applications; bottlebrush polymers undergo significant molecular extension in stretched, soft elastomers, in out-of-equilibrium environments during solution processing or in confinement-induced stretching. Unlike linear polymer chains where the molecular origin of this extension is well understood, it remains a challenge to connect molecular bottlebrush architecture to forceextension behavior. In this paper, we present results from Monte Carlo simulations on bottlebrush polymers subjected to a constant pulling force and determine force-extension curves as a function of side-chain length. We show that different bottlebrush architectures exhibit a variety of force-extension behaviors. To understand bottlebrush elasticity, we compare with a parameterized wormlike cylinder implicit side chain model. This demonstrates the emergence of two distinct modes of bottlebrush stretching; at low forces, we demonstrate both linear and non-linear regimes corresponding to stretching the overall cylindrical shape of the molecule, and at high forces, there is specific extension of internal degrees of molecular freedom corresponding to the bottlebrush backbone. This two-regime molecular picture provides insight valuable to the molecular design of bottlebrush materials.

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“…Magnetic tweezers typically apply forces on the order of 0.01-10 pN and thus are sensitive to structure on length scales between $1 and 100 s of nm. Because of this long length scale sensitivity, magnetic tweezers have succeeded in measuring the structural changes induced by side chains in a synthetic polymer bottlebrush (28).…”

Section: Introductionmentioning

confidence: 99%

Single-Molecule Stretching Shows Glycosylation Sets Tension in the Hyaluronan-Aggrecan Bottlebrush

Innes-Gold

Berezney

Saleh

2020

Biophysical Journal

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Large bottlebrush complexes formed from the polysaccharide hyaluronan (HA) and the proteoglycan aggrecan contribute to cartilage compression resistance and are necessary for healthy joint function. A variety of mechanical forces act on these complexes in the cartilage extracellular matrix, motivating the need for a quantitative description that links their structure and mechanical response. Studies using electron microscopy have imaged the HA-aggrecan brush but require adsorption to a surface, dramatically altering the complex from its native conformation. We use magnetic tweezers force spectroscopy to measure changes in extension and mechanical response of an HA chain as aggrecan monomers bind and form a bottlebrush. This technique directly measures changes undergone by a single complex with time and under varying solution conditions. Upon addition of aggrecan, we find a large swelling effect manifests when the HA chain is under very low external tension (i.e., stretching forces less than $1 pN). We use models of force-extension behavior to show that repulsion between the aggrecans induces an internal tension in the HA chain. Through reference to theories of bottlebrush polymer behavior, we demonstrate that the experimental values of internal tension are consistent with a polydisperse aggrecan population, likely caused by varying degrees of glycosylation. By enzymatically deglycosylating the aggrecan, we show that aggrecan glycosylation is the structural feature that causes HA stiffening. We then construct a simple stochastic binding model to show that variable glycosylation leads to a wide distribution of internal tensions in HA, causing variations in the mechanics at much longer length scales. Our results provide a mechanistic picture of how flexibility and size of HA and aggrecan lead to the brush architecture and mechanical properties of this important component of cartilage.

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Scale-Dependent Stiffness and Internal Tension of a Model Brush Polymer

Cited by 12 publications

References 31 publications

Single polymer dynamics for molecular rheology

Single polymer dynamics for molecular rheology

Two Stretching Regimes in the Elasticity of Bottlebrush Polymers

Single-Molecule Stretching Shows Glycosylation Sets Tension in the Hyaluronan-Aggrecan Bottlebrush

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