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Jeon S, Kamble Y, Xu Z, Khasbaatar A, Hwang C, Lee JH, Shi J, Rogers SA, Guironnet D, Diao Y. Large modulation of the bottlebrush diblock copolymer morphology and structural color through solvent selectivity. SOFT MATTER 2025. [PMID: 39982413 DOI: 10.1039/d4sm01495b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2025]
Abstract
Bottlebrush block copolymers (BBCPs), characterized by densely grafted side chains along their backbone, have emerged as promising materials for structural color applications. Their unique architecture prevents entanglement and facilitates rapid assembly kinetics, enabling the formation of various photonic crystals with high tunability of structural color from the visible to the infrared range. However, accessing non-1D structures has been largely limited to synthetic approaches. In this paper, we report large modulation of a microphase separated morphology of the polystyrene-b-polylactide (PS-b-PLA) BBCP using a single material by exploiting selective solubility of the two blocks in a series of structurally similar solvents. Combining optical spectroscopy, electron microscopy, photoinduced force microscopy and X-ray scattering, we unveil the microstructural evolution as dependent on solvent selectivity. Furthermore, we uncovered the mechanisms underlying the differences in assembly, where highly selective solvents induce sidechain aggregation, altering the volume fraction and facilitating the formation of non-1D structures.
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Kamani KM, Shim YH, Griebler J, Narayanan S, Zhang Q, Leheny RL, Harden JL, Deptula A, Espinosa-Marzal RM, Rogers SA. Linking structural and rheological memory in disordered soft materials. SOFT MATTER 2025; 21:750-759. [PMID: 39791209 DOI: 10.1039/d4sm00953c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2025]
Abstract
Linking the macroscopic flow properties and nanoscopic structure is a fundamental challenge to understanding, predicting, and designing disordered soft materials. Under small stresses, these materials are soft solids, while larger loads can lead to yielding and the acquisition of plastic strain, which adds complexity to the task. In this work, we connect the transient structure and rheological memory of a colloidal gel under cyclic shearing across a range of amplitudes via a generalized memory function using rheo-X-ray photon correlation spectroscopy (rheo-XPCS). Our rheo-XPCS data show that the nanometer scale aggregate-level structure recorrelates whenever the change in recoverable strain over some interval is zero. The macroscopic recoverable strain is therefore a measure of the nano-scale structural memory. We further show that yielding in disordered colloidal materials is strongly heterogeneous and that memories of prior deformation can exist even after the material has been subjected to flow.
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Adorno GR, Timmer KB, Chang RASH, Shi J, Rogers SA, Harley BAC. Shaping the mechanical properties of a gelatin hydrogel interface via amination. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.10.14.618299. [PMID: 39464090 PMCID: PMC11507719 DOI: 10.1101/2024.10.14.618299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/29/2024]
Abstract
Injuries to musculoskeletal interfaces, such as the tendon-to-bone insertion of the rotator cuff, present significant physiological and clinical challenges for repair due to complex gradients of structure, composition, and cellularity. Advances in interface tissue engineering require stratified biomaterials able to both provide local instructive signals to support multiple tissue phenotypes while also reducing the risk of strain concentrations and failure at the transition between dissimilar materials. Here, we describe adaptation of a thiolated gelatin (Gel-SH) hydrogel via selective amination of carboxylic acid subunits on the gelatin backbone. The magnitude and kinetics of HRP-mediated primary crosslinking and carbodiimide-mediated secondary crosslinking reactions can be tuned through amination and thiolation of carboxylic acid subunits on the gelatin backbone. We also show that a stratified biomaterial comprised of mineralized (bone-mimetic) and non-mineralized (tendon-mimetic) collagen scaffold compartments linked by an aminated Gel-SH hydrogel demonstrate improved mechanical performance and reduced strain concentrations. Together, these results highlight significant mechanical advantages that can be derived from modifying the gelatin macromer via controlled amination and thiolation and suggest an avenue for tuning the mechanical performance of hydrogel interfaces within stratified biomaterials.
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Kamani KM, Rogers SA. Brittle and ductile yielding in soft materials. Proc Natl Acad Sci U S A 2024; 121:e2401409121. [PMID: 38776367 PMCID: PMC11145261 DOI: 10.1073/pnas.2401409121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2024] [Accepted: 04/29/2024] [Indexed: 05/25/2024] Open
Abstract
Many soft materials yield under mechanical loading, but how this transition from solid-like behavior to liquid-like behavior occurs can vary significantly. Understanding the physics of yielding is of great interest for the behavior of biological, environmental, and industrial materials, including those used as inks in additive manufacturing and muds and soils. For some materials, the yielding transition is gradual, while others yield abruptly. We refer to these behaviors as being ductile and brittle. The key rheological signatures of brittle yielding include a stress overshoot in steady-shear-startup tests and a steep increase in the loss modulus during oscillatory amplitude sweeps. In this work, we show how this spectrum of yielding behaviors may be accounted for in a continuum model for yield stress materials by introducing a parameter we call the brittility factor. Physically, an increased brittility decreases the contribution of recoverable deformation to plastic deformation, which impacts the rate at which yielding occurs. The model predictions are successfully compared to results of different rheological protocols from a number of real yield stress fluids with different microstructures, indicating the general applicability of the phenomenon of brittility. Our study shows that the brittility of soft materials plays a critical role in determining the rate of the yielding transition and provides a simple tool for understanding its effects under various loading conditions.
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Jeon S, Kamble YL, Kang H, Shi J, Wade MA, Patel BB, Pan T, Rogers SA, Sing CE, Guironnet D, Diao Y. Direct-ink-write cross-linkable bottlebrush block copolymers for on-the-fly control of structural color. Proc Natl Acad Sci U S A 2024; 121:e2313617121. [PMID: 38377215 PMCID: PMC10907314 DOI: 10.1073/pnas.2313617121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 01/16/2024] [Indexed: 02/22/2024] Open
Abstract
Additive manufacturing capable of controlling and dynamically modulating structures down to the nanoscopic scale remains challenging. By marrying additive manufacturing with self-assembly, we develop a UV (ultra-violet)-assisted direct ink write approach for on-the-fly modulation of structural color by programming the assembly kinetics through photo-cross-linking. We design a photo-cross-linkable bottlebrush block copolymer solution as a printing ink that exhibits vibrant structural color (i.e., photonic properties) due to the nanoscopic lamellar structures formed post extrusion. By dynamically modulating UV-light irradiance during printing, we can program the color of the printed material to access a broad spectrum of visible light with a single ink while also creating color gradients not previously possible. We unveil the mechanism of this approach using a combination of coarse-grained simulations, rheological measurements, and structural characterizations. Central to the assembly mechanism is the matching of the cross-linking timescale with the assembly timescale, which leads to kinetic trapping of the assembly process that evolves structural color from blue to red driven by solvent evaporation. This strategy of integrating cross-linking chemistry and out-of-equilibrium processing opens an avenue for spatiotemporal control of self-assembled nanostructures during additive manufacturing.
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Mahmoudabadbozchelou M, Kamani KM, Rogers SA, Jamali S. Unbiased construction of constitutive relations for soft materials from experiments via rheology-informed neural networks. Proc Natl Acad Sci U S A 2024; 121:e2313658121. [PMID: 38170750 PMCID: PMC10786310 DOI: 10.1073/pnas.2313658121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 12/03/2023] [Indexed: 01/05/2024] Open
Abstract
The ability to concisely describe the dynamical behavior of soft materials through closed-form constitutive relations holds the key to accelerated and informed design of materials and processes. The conventional approach is to construct constitutive relations through simplifying assumptions and approximating the time- and rate-dependent stress response of a complex fluid to an imposed deformation. While traditional frameworks have been foundational to our current understanding of soft materials, they often face a twofold existential limitation: i) Constructed on ideal and generalized assumptions, precise recovery of material-specific details is usually serendipitous, if possible, and ii) inherent biases that are involved by making those assumptions commonly come at the cost of new physical insight. This work introduces an approach by leveraging recent advances in scientific machine learning methodologies to discover the governing constitutive equation from experimental data for complex fluids. Our rheology-informed neural network framework is found capable of learning the hidden rheology of a complex fluid through a limited number of experiments. This is followed by construction of an unbiased material-specific constitutive relation that accurately describes a wide range of bulk dynamical behavior of the material. While extremely efficient in closed-form model discovery for a real-world complex system, the model also provides insight into the underpinning physics of the material.
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Le ANM, Erturk MY, Shim YH, Rogers SA, Kokini J. A critical study of the nonlinear rheological properties in major classes of foods using the Sequence of Physical Processes (SPP) method and the Fourier Transform Coupled with Chebyshev Decomposition (FTC) method. Food Res Int 2023; 174:113587. [PMID: 37986453 DOI: 10.1016/j.foodres.2023.113587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 10/11/2023] [Accepted: 10/13/2023] [Indexed: 11/22/2023]
Abstract
The nonlinear rheological behaviors of three different classes of foods (emulsion, suspension, and elastic network) were studied and analyzed using the Rogers Sequence of Physical Processes (SPP) method and the Ewoldt-McKinley method of coupling Fourier Transform with Chebyshev Decomposition (FTC). SPP analysis led to instantaneous rheological parameters G't and G″t at any point in time, providing a more accurate picture of the linear viscoelastic region and crossover points by the 3D amplitude sweep. When G't is plotted against G″t, the resulting graph is a deltoid which offers a detailed and distinctive intracycle behavior of each class of food. Analyzing the revolution of deltoids with increasing strain allows for the determination of a critical strain, beyond which irreversible network breakdown occurs. The strain range between the linear viscoelastic limit and the critical strain found in SPP is comparable to the MAOS region as determined with FTC. Under increasing amplitude, predominantly elastic networks showed a gradual structural rearrangement, while more erratic and abrupt changes were observed in the suspension and emulsion we studied. Under increasing frequency, elastic responses dominate viscous responses in all samples due to the shorter experimental time, allowing less relaxation.
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Cho NH, Shi J, Murphy RP, Riley JK, Rogers SA, Richards JJ. Extracting microscopic insight from transient dielectric measurements during large amplitude oscillatory shear. SOFT MATTER 2023. [PMID: 37681714 DOI: 10.1039/d3sm00786c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/09/2023]
Abstract
Probing the transient microstructure of soft matter far from equilibrium is an ongoing challenge to understanding material processing. In this work, we investigate inverse worm-like micelles undergoing large amplitude oscillatory shear using time-resolved dielectric spectroscopy. By controlling the Weissenburg number, we compare the non-linear microstructure response of branched and unbranched worm-like micelles and isolate distinct elastic effects that manifest near flow reversal. We validate our dielectric measurements with small angle neutron scattering and employ sequence of physical processes to disentangle the elastic and viscous contributions of the stress.
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9
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Donley GJ, Narayanan S, Wade MA, Park JD, Leheny RL, Harden JL, Rogers SA. Investigation of the yielding transition in concentrated colloidal systems via rheo-XPCS. Proc Natl Acad Sci U S A 2023; 120:e2215517120. [PMID: 37094149 PMCID: PMC10161110 DOI: 10.1073/pnas.2215517120] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 02/04/2023] [Indexed: 04/26/2023] Open
Abstract
We probe the microstructural yielding dynamics of a concentrated colloidal system by performing creep/recovery tests with simultaneous collection of coherent scattering data via X-ray Photon Correlation Spectroscopy (XPCS). This combination of rheology and scattering allows for time-resolved observations of the microstructural dynamics as yielding occurs, which can be linked back to the applied rheological deformation to form structure-property relations. Under sufficiently small applied creep stresses, examination of the correlation in the flow direction reveals that the scattering response recorrelates with its predeformed state, indicating nearly complete microstructural recovery, and the dynamics of the system under these conditions slows considerably. Conversely, larger creep stresses increase the speed of the dynamics under both applied creep and recovery. The data show a strong connection between the microstructural dynamics and the acquisition of unrecoverable strain. By comparing this relationship to that predicted from homogeneous, affine shearing, we find that the yielding transition in concentrated colloidal systems is highly heterogeneous on the microstructural level.
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Singh PK, Pacholski ML, Gu J, Go YK, Singhal G, Leal C, Braun PV, Patankar KA, Drumright R, Rogers SA, Schroeder CM. Designing Multicomponent Polymer Colloids for Self-Stratifying Films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11160-11170. [PMID: 36053575 DOI: 10.1021/acs.langmuir.2c00855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Aqueous polymer colloids known as latexes are widely used in coating applications. Multicomponent latexes comprised of two incompatible polymeric species organized into a core-shell particle morphology are a promising system for self-stratifying coatings that spontaneously partition into multiple layers, thereby yielding complex structured coatings requiring only a single application step. Developing new materials for self-stratifying coatings requires a clear understanding of the thermodynamic and kinetic properties governing phase separation and polymeric species transport. In this work, we study phase separation and self-stratification in polymer films based on multicomponent acrylic (shell) and acrylic-silicone (core) latex particles. Our results show that the molecular weight of the shell polymer and heat aging conditions of the film critically determine the underlying transport phenomena, which ultimately controls phase separation in the film. Unentangled shell polymers result in efficient phase separation within hours with heat aging at reasonable temperatures, whereas entangled shell polymers effectively inhibit phase separation even under extensive heat aging conditions over a period of months due to kinetic limitations. Transmission electron microscopy is used to track morphological changes as a function of thermal aging. Interestingly, our results show that the rheological properties of the latex films are highly sensitive to morphology, and linear shear rheology is used to understand morphological changes. Overall, these results highlight the importance of bulk rheology as a simple and effective tool for understanding changes in morphology in multicomponent latex films.
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Deng YH, Ricciardulli T, Won J, Wade MA, Rogers SA, Boppart SA, Flaherty DW, Kong H. Self-locomotive, antimicrobial microrobot (SLAM) swarm for enhanced biofilm elimination. Biomaterials 2022; 287:121610. [PMID: 35696784 PMCID: PMC9763052 DOI: 10.1016/j.biomaterials.2022.121610] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Accepted: 05/29/2022] [Indexed: 12/20/2022]
Abstract
Biofilm is a major cause of infections and infrastructure deterioration, largely due to molecular diffusion restrictions that hamper the antimicrobial activity of traditional antibiotics and disinfectants. Here, we present a self-locomotive, antimicrobial microrobot (SLAM) swarm that can penetrate, fracture, and detach biofilm and, in turn, nullify bacterial resistance to antibiotics. The SLAM is assembled by loading a controlled mass of manganese oxide nanosheets on diatoms with the polydopamine binder. In hydrogen peroxide solution, SLAMs produce oxygen bubbles that generate thrust to penetrate the rigid and dense Pseudomonas aeruginosa biofilm and self-assemble into a swarm that repeatedly surrounds, expands, and bursts oxygen bubbles. The resulting cavities continue to deform and fracture extracellular polymeric substances from microgrooved silicone substrates and wounded skin explants while decreasing the number of viable bacterial cells. Additionally, SLAM allows irrigating water or antibiotics to access the residual biofilm better, thus enhancing the synergistic efficacy in killing up to 99.9% of bacterial cells.
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12
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Erturk MY, Rogers SA, Kokini J. Comparison of Sequence of Physical Processes (SPP) and Fourier Transform Coupled with Chebyshev Polynomials (FTC) methods to Interpret Large Amplitude Oscillatory Shear (LAOS) Response of Viscoelastic Doughs and Viscous Pectin Solution. Food Hydrocoll 2022. [DOI: 10.1016/j.foodhyd.2022.107558] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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13
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Mahmoudabadbozchelou M, Kamani KM, Rogers SA, Jamali S. Digital rheometer twins: Learning the hidden rheology of complex fluids through rheology-informed graph neural networks. Proc Natl Acad Sci U S A 2022; 119:e2202234119. [PMID: 35544690 PMCID: PMC9171907 DOI: 10.1073/pnas.2202234119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 03/28/2022] [Indexed: 01/12/2023] Open
Abstract
SignificanceScience-based data-driven methods that can describe the rheological behavior of complex fluids can be transformative across many disciplines. Digital rheometer twins, which are developed here, can significantly reduce the cost, time, and energy required to characterize complex fluids and predict their future behavior. This is made possible by combining two different methods of informing neural networks with the rheological underpinnings of a system, resulting in quantitative recovery of a gel's response to different flow protocols. The platform developed here is general enough that it can be extended to areas well beyond complex fluids modeling.
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14
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Han M, Rogers SA, Espinosa-Marzal RM. Rheological Characteristics of Ionic Liquids under Nanoconfinement. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2961-2971. [PMID: 35220714 DOI: 10.1021/acs.langmuir.1c03460] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
While the dynamic properties of ionic liquids (ILs) in nanoconfinement play a crucial role in the performance of IL-based electrochemical and mechanical devices, experimental work mostly falls short at reporting "solid-like" versus "liquid-like" behavior of confined ILs. The present work is the first to conduct frequency-sweep oscillatory-shear rheology on IL nanofilms, reconciling the solid-versus-liquid debate and revealing the importance of shear rate in the behavior. We disentangle and analyze the viscoelasticity of nanoconfined ILs and shed light on their relaxation mechanisms. Furthermore, a master curve describes the scaling of the dynamic behavior of four (non-hydrogen-bonding) ILs under nanoconfinement and reveals the role of the compressibility of the flow units.
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Kamani K, Donley GJ, Rogers SA. Unification of the Rheological Physics of Yield Stress Fluids. PHYSICAL REVIEW LETTERS 2021; 126:218002. [PMID: 34114843 DOI: 10.1103/physrevlett.126.218002] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 03/26/2021] [Accepted: 04/28/2021] [Indexed: 05/27/2023]
Abstract
The physics above and below the yield stress is unified by a simple model for viscoplasticity that accounts for the nonlinear rheology of multiple yield stress fluids. The model has a rate-dependent relaxation time, allows for plastic deformation below the yield stress, and indicates that rapid elastic deformation aids yielding. A range of commonly observed rheological behaviors are predicted, including the smooth overshoot in the loss modulus and the recently discovered contributions from recoverable and unrecoverable strains in amplitude sweeps.
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Chen Y, Rogers SA, Narayanan S, Harden JL, Leheny RL. Microscopic ergodicity breaking governs the emergence and evolution of elasticity in glass-forming nanoclay suspensions. Phys Rev E 2020; 102:042619. [PMID: 33212706 DOI: 10.1103/physreve.102.042619] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 10/10/2020] [Indexed: 11/07/2022]
Abstract
We report a study combining x-ray photon correlation spectroscopy (XPCS) with in situ rheology to investigate the microscopic dynamics and mechanical properties of aqueous suspensions of the synthetic hectorite clay Laponite, which is composed of charged, nanometer-scale, disk-shaped particles. The suspensions, with particle concentrations ranging from 3.25 to 3.75 wt %, evolve over time from a fluid to a soft glass that displays aging behavior. The XPCS measurements characterize the localization of the particles during the formation and aging of the soft-glass state. The fraction of localized particles, f_{0}, increases rapidly during the early formation stage and grows more slowly during subsequent aging, while the characteristic localization length r_{loc} steadily decreases. Despite the strongly varying rates of aging at different concentrations, both f_{0} and r_{loc} scale with the elastic shear modulus G^{'} in a manner independent of concentration. During the later aging stage, the scaling between r_{loc} and G^{'} agrees quantitatively with a prediction of naive mode coupling theory. Breakdown of agreement with the theory during the early formation stage indicates the prevalence of dynamic heterogeneity, suggesting the soft solid forms through precursors of dynamically localized clusters.
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Walsh DJ, Wade MA, Rogers SA, Guironnet D. Challenges of Size-Exclusion Chromatography for the Analysis of Bottlebrush Polymers. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c01357] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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18
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Wade MA, Walsh D, Lee JCW, Kelley E, Weigandt K, Guironnet D, Rogers SA. Color, structure, and rheology of a diblock bottlebrush copolymer solution. SOFT MATTER 2020; 16:4919-4931. [PMID: 32393953 PMCID: PMC11253116 DOI: 10.1039/d0sm00397b] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A structure-property-process relation is established for a diblock bottlebrush copolymer solution, through a combination of rheo-neutron scattering, imaging, and rheological measurements. Polylactic acid-b-polystyrene diblock bottlebrush copolymers were dispersed in toluene with a concentration of 175 mg ml-1, where they self-assembled into a lamellar phase. All measurements were carried out at 5 °C. The solution color, as observed in reflection, is shown to be a function of the shear rate. Under equilibrium and near-equilibrium conditions, the solution has a green color. At low shear rates the solution remains green, while at intermediate rates the solution is cyan. At the highest rates applied the solution is indigo. The lamellar spacing is shown to be a decreasing function of shear rate, partially accounting for the color change. The lamellae are oriented 'face-on' with the wall under quiescence and low shear rates, while a switch to 'edge-on' is observed at the highest shear rates, where the reflected color disappears. The intramolecular distance between bottlebrush polymers does not change with shear rate, although at high shear rates, the bottlebrush polymers are preferentially aligned in the vorticity direction within the lamellae. We therefore form a consistent relation between structure and function, spanning a wide range of length scales and shear rates.
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Lee JCW, Hong YT, Weigandt KM, Kelley EG, Kong H, Rogers SA. Strain shifts under stress-controlled oscillatory shearing in theoretical, experimental, and structural perspectives: Application to probing zero-shear viscosity. JOURNAL OF RHEOLOGY 2019; 63:10.1122/1.5111358. [PMID: 39411405 PMCID: PMC11474985 DOI: 10.1122/1.5111358] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 09/08/2019] [Indexed: 10/19/2024]
Abstract
Rheological measurements in which the applied stress or strain is oscillated are widely used to interrogate viscoelastic properties due to the independent control over the time scale and length scale afforded by changes in amplitude and frequency. Taking a nontraditional approach, we treat stress-controlled oscillatory tests as creep tests with transiently varying stress and apply an analysis typically used for steady creep and recovery experiments. Defining zero strain as the state prior to external shearing, it is shown that strain responses to small-amplitude oscillatory stressing are naturally shifted from the starting point by an amount proportional to the phase of the applied stress. The phenomenology is experimentally observed with entangled polymerlike micelles and polyethylene oxide solutions. A theory of strain shifting in the steady alternating state is provided based on recovery rheology, where differences between total strain and recoverable strains are acknowledged. User-controlled variables, such as the amplitude of the stress, the angular frequency, and the phase of the stress, as well a lone material parameter, the zero-shear viscosity, are shown to dictate the amount of shifting. A rapid and efficient approach of determining the zero-shear viscosity is, therefore, presented. We investigate the microstructural evolution via in situ small-angle neutron scattering when strain shifting appears. The microscopic orientation is shown to correlate to the recoverable strain independent of the shifting. Additional measurements are carried out on collagen, pluronic-hyaluronic acid, alginate gels, and polystyrene melts to show the generic nature of the strain shift phenomenon. In addition, we demonstrate that the strain-shift knowledge can be applied to determine the horizontal shift factor in time-temperature superposition, free of any numerical fitting procedures.
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Sandford GN, Day BT, Rogers SA. Racing Fast and Slow: Defining the Tactical Behavior That Differentiates Medalists in Elite Men's 1,500 m Championship Racing. Front Sports Act Living 2019; 1:43. [PMID: 33344966 PMCID: PMC7739615 DOI: 10.3389/fspor.2019.00043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 09/20/2019] [Indexed: 12/04/2022] Open
Abstract
Background: 1,500 m running has long been a blue ribbon event of track championship racing. The eventual medalists employ common tactical behaviors such as a fast sustained pace from the start (gun-to-tape), or, slow initial laps that precede a precisely timed race kick. Before the kick, there are positional changes caused by surging, that can go uncharacterized. The inter-relationship of surge events, tactical positioning, and kick execution may have important implications for eventual medal winning outcomes and require further definition. Methods: In a randomized order, three middle-distance running experts were provided publically available video (YouTube) of 16 men's 1,500 m championship races across, European, World and Olympic championships. Each expert determined the occurrence of surges (defined as any point in the 1,500 m after the first 300 m where an athlete repositions by ≥3 places; or noticeably dictates a raise in the pace from the front) and the race kick. Following a second level verification of expert observations, tactical behaviors (quantity and distance marker within each race) mean distance from the finish were compared between fast (≤3:34.00, n = 5), medium (>3:34.00– ≤3:41.99, n = 7) and slow (≥3:42.00, n = 4) race categories. Results: Before the race kick, there were more surges in slow (5 ± 1.7, mean ±90% confidence limits) vs. fast races (1 ± 0.4, very large difference, very likely). The final surge before the race kick occurred earlier in fast (704 ± 133 m from the finish) vs. medium (427 ± 83 m, large difference, most likely), and slow races (370 ± 137 m, large difference, most likely). At initiation of the race kick in fast races, large positional differences were found between eventual gold (2 ± 1.2; likely) and silver (2.2 ± 1.6; likely) vs. bronze medalists (4.4 ± 1.2). In slow races, positional differences were unclear between eventual gold (4.3 ± 4.7), silver (4.8 ± 4.8) and bronze medalists (5.3 ± 1.5). Regardless of category, the race kick occurred on the last lap, with unclear differences between fast 244 ± 92 m medium 243 ± 56 m and slow 236 ± 142 m races. Conclusions: Presenting tactical behaviors by race categorization (slow, medium, fast race times), provides a novel understanding of the nuance of racing tactics. The present findings highlight the importance of considering within race athlete decision making across multiple-race scenarios during championship preparation.
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Lee JC, Porcar L, Rogers SA. Recovery rheology via rheo‐SANS: Application to step strains under out‐of‐equilibrium conditions. AIChE J 2019. [DOI: 10.1002/aic.16797] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Lee JCW, Weigandt KM, Kelley EG, Rogers SA. Structure-Property Relationships via Recovery Rheology in Viscoelastic Materials. PHYSICAL REVIEW LETTERS 2019; 122:248003. [PMID: 31322410 DOI: 10.1103/physrevlett.122.248003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 04/15/2019] [Indexed: 06/10/2023]
Abstract
The recoverable strain is shown to correlate to the temporal evolution of microstructure via time-resolved small-angle neutron scattering and dynamic shear rheology. Investigating two distinct polymeric materials of wormlike micelles and fibrin network, we demonstrate that, in addition to the nonlinear structure-property relationships, the shear and normal stress evolution is dictated by the recoverable strain. A distinct sequence of physical processes under large amplitude oscillatory shear (LAOS) is identified that clearly contains information regarding both the steady-state flow curve and the linear-regime frequency sweep, contrary to most interpretations that LAOS responses are either distinct from or somehow intermediate between the two cases. This work provides a physically motivated and straightforward path to further explore the structure-property relationships of viscoelastic materials under dynamic flow conditions.
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23
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Sun Han Chang R, Lee JCW, Pedron S, Harley BAC, Rogers SA. Rheological Analysis of the Gelation Kinetics of an Enzyme Cross-linked PEG Hydrogel. Biomacromolecules 2019; 20:2198-2206. [PMID: 31046247 PMCID: PMC6765384 DOI: 10.1021/acs.biomac.9b00116] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The diverse requirements of hydrogels for tissue engineering motivate the development of cross-linking reactions to fabricate hydrogel networks with specific features, particularly those amenable to the activity of biological materials (e.g., cells, proteins) that do not require exposure to UV light. We describe gelation kinetics for a library of thiolated poly(ethylene glycol) sulfhydryl hydrogels undergoing enzymatic cross-linking via horseradish peroxidase, a catalyst-driven reaction activated by hydrogen peroxide. We report the use of small-amplitude oscillatory shear (SAOS) to quantify gelation kinetics as a function of reaction conditions (hydrogen peroxide and polymer concentrations). We employ a novel approach to monitor the change of viscoelastic properties of hydrogels over the course of gelation (Δ tgel) via the time derivative of the storage modulus (d G'/d t). This approach, fundamentally distinct from traditional methods for defining a gel point, quantifies the time interval over which gelation events occur. We report that gelation depends on peroxide and polymer concentrations as well as system temperature, where the effects of hydrogen peroxide tend to saturate over a critical concentration. Further, this cross-linking reaction can be reversed using l-cysteine for rapid cell isolation, and the rate of hydrogel dissolution can be monitored using SAOS.
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Ching-Wei Lee J, Park JD, Rogers SA. Studying Large Amplitude Oscillatory Shear Response of Soft Materials. J Vis Exp 2019. [PMID: 31081809 DOI: 10.3791/58707] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl sulfoxide (DMSO) and xanthan gum in water - two concentrated polymer solutions used as viscosifiers in foods, enhanced oil recovery, and soil remediation. Understanding the nonlinear rheological behavior of soft materials is important in the design and controlled manufacturing of many consumer products. It is shown how the response to LAOS of these polymer solutions can be interpreted in terms of a clear transition from linear viscoelasticity to viscoplastic deformation and back again during a period. The LAOS results are analyzed via the fully quantitative Sequence of Physical Processes (SPP) technique, using free MATLAB-based software. A detailed protocol of performing a LAOS measurement with a commercial rheometer, analyzing nonlinear stress responses with the freeware, and interpreting physical processes under LAOS is presented. It is further shown that, within the SPP framework, a LAOS response contains information regarding the linear viscoelasticity, the transient flow curves, and the critical strain responsible for the onset of nonlinearity.
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25
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Dutta S, Wade MA, Walsh DJ, Guironnet D, Rogers SA, Sing CE. Dilute solution structure of bottlebrush polymers. SOFT MATTER 2019; 15:2928-2941. [PMID: 30724969 DOI: 10.1039/c9sm00033j] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Bottlebrush polymers are a class of macromolecules that have recently found use in a wide variety of materials, ranging from lubricating brushes and nanostructured coatings to elastomeric gels that exhibit structural colors. These polymers are characterized by dense branches extending from a central backbone and thus have properties distinct from linear polymers. It remains a challenge to specifically understand conformational properties of these molecules, due to the wide range of architectural parameters that can be present in a system, and thus there is a need to accurately characterize and model these molecules. In this paper, we use a combination of viscometry, light scattering, and computer simulations to gain insight into the conformational properties of dilute solution bottlebrush polymers. We focus on a series of model bottlebrushes consisting of a poly(norbornene) (PNB) backbone with poly(lactic acid) (PLA) side chains. We demonstrate that intrinsic viscosity and hydrodynamic radius are experimental observations sensitive to molecular architecture, exhibiting distinct differences with different choices of branches and backbone lengths. Informed by the atomistic structure of this PNB-PLA system, we rationalize a coarse-grained simulation model that we evaluate using a combination of Brownian dynamics and Monte Carlo simulations. We show that this exhibits quantitative matching to experimental results, enabling us to characterize the overall shape of the bottlebrush via a number of metrics that can be extended to more general bottlebrush architectures.
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