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Biswas B, Mitra D, Kp F, Bhat S, Chatterji A, Kumaraswamy G. Rigidity Dictates Spontaneous Helix Formation of Thermoresponsive Colloidal Chains in Poor Solvent. ACS NANO 2021; 15:19702-19711. [PMID: 34890180 DOI: 10.1021/acsnano.1c07048] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The formation of helical motifs typically requires specific directional interactions. Here, we demonstrate that isotropic interparticle attraction can drive self-assembly of colloidal chains into thermo-reversible helices, for chains with a critical level of backbone rigidity. We prepare thermoresponsive colloidal chains by cross-linking PNIPAM microgel-coated polystyrene colloids ("monomers"), aligned in an AC electric field. We control the chain rigidity by varying cross-linking time. Above the LCST of PNIPAM, there is an effective attraction between monomers so that the colloidal chains are in a bad solvent. On heating, the chains decrease in size. For the most rigid chains, the decrease is modest and is not accompanied by a change in shape. Much less rigid chains form relatively compact structures, resulting in a large increase in the local monomer density. Unusually, chains with intermediate rigidity spontaneously assemble into helical structures. The chain helicity increases with temperature and plateaus above the collapse transition temperature of the microgel particles. We simulate a minimal model that captures the spontaneous emergence of the helical conformations of the polymeric chain and provides insight into this shape transition. Our work suggests that a purely mechanical instability for semiflexible filaments can drive helix formation, without the need to invoke directional interactions.
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Affiliation(s)
- Bipul Biswas
- PSE Division, CSIR-NCL Pune, Dr. Homi Bhaba Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Debarshi Mitra
- Department of Physics, IISER-Pune, Dr. Homi Bhaba Road, Pune 411008, India
| | - Fayis Kp
- PSE Division, CSIR-NCL Pune, Dr. Homi Bhaba Road, Pune 411008, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Suresh Bhat
- PSE Division, CSIR-NCL Pune, Dr. Homi Bhaba Road, Pune 411008, India
| | - Apratim Chatterji
- Department of Physics, IISER-Pune, Dr. Homi Bhaba Road, Pune 411008, India
- Center for Energy Science, IISER-Pune, Dr. Homi Bhaba Road, Pune 411008, India
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Mitra D, Chatterji A. Transient helix formation in charged semiflexible polymers without confinement effects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 33:044001. [PMID: 32987379 DOI: 10.1088/1361-648x/abbc32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 09/28/2020] [Indexed: 06/11/2023]
Abstract
Switching on generic interactions e.g. the Coulomb potential or other long ranged spherically symmetric repulsive interactions between monomers of bead-spring model of a semi-flexible polymer induce instabilities in a semiflexible polymer chain to form transient helical structures. Our proposed mechanism could explain the spontaneous emergence of helical order in stiff (bio-) polymers as a chain gets charged from a neutral state. But since the obtained helical structures dissolve away with time, hydrogen bonding (or other additional mechanisms), would be required to form stabilized helical structures as observed in nature (such as in biological macro-molecules). The emergence of the helix is independent of the molecular details of the monomer constituent. The key factors which control the emergence of the helical structure is the persistence length and the charge density. We have avoided using torsional potentials to obtain the transient helical structures. Moreover, we can drive the semiflexible polymer to form helices in a recurring manner by periodically increasing and decreasing the effective charge of the monomers. If the two polymer ends are tethered to two surfaces separated by a distance equal to the contour length of the polymeric chain, which could be in the range 10 nm-μ, the life time of the helical structures formed is increased.
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Affiliation(s)
- Debarshi Mitra
- Department of Physics, IISER-Pune, Dr Homi Bhaba Road, Pune-411008, India
| | - Apratim Chatterji
- Department of Physics, IISER-Pune, Dr Homi Bhaba Road, Pune-411008, India
- Center for Energy Science, IISER-Pune, Dr Homi Bhaba Road, Pune-411008, India
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Chelakkot R, Winkler RG, Gompper G. Flow-induced helical coiling of semiflexible polymers in structured microchannels. PHYSICAL REVIEW LETTERS 2012; 109:178101. [PMID: 23215225 DOI: 10.1103/physrevlett.109.178101] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Indexed: 06/01/2023]
Abstract
The conformations of semiflexible (bio)polymers are studied in flow-through geometrically structured microchannels. Using mesoscale hydrodynamics simulations, we show that the polymer undergoes a rod-to-helix transition as it moves from the narrow high-velocity region into the wide low-velocity region of the channel. The transient helix formation is the result of a nonequilibrium and nonstationary buckling transition of the semiflexible polymer, which is subjected to a compressive force originating from the fluid-velocity variation in the channel. The helix properties depend on the diameter ratio of the channel, the polymer bending rigidity, and the flow strength.
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Affiliation(s)
- Raghunath Chelakkot
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany
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Raghu RC, Schofield J. Simulation of tethered oligomers in nanochannels using multi-particle collision dynamics. J Chem Phys 2012; 137:014901. [PMID: 22779677 DOI: 10.1063/1.4731662] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of a high Reynold's number, pressure-driven flow of a compressible gas on the conformation of an oligomer tethered to the wall of a square channel is studied under both ideal solvent and poor solvent conditions using a hybrid multiparticle collision dynamics and molecular dynamics algorithm. Unlike previous studies, the flow field contains an elongational component in addition to a shear component as well as fluid slip near the walls and results in a Schmidt number for the polymer beads that is less than unity. In both solvent regimes the oligomer is found to extend in the direction of flow. Under the ideal solvent conditions, torsional twisting of the chain and aperiodic cyclical dynamics are observed for the end of the oligomer. Under poor solvent conditions, a metastable helix forms in the end of the chain despite the lack of any attractive potential between beads in the oligomeric chain. The formation of the helix is postulated to be the result of a solvent induced chain collapse that has been confined to a single dimension by a strong flow field.
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Affiliation(s)
- Riyad Chetram Raghu
- Chemical Physics Theory Group, Department of Chemistry, University of Toronto, 80 Saint George Street, Ontario M5S 3H6, Canada.
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Das S, Chakraborty S. Probing solvation decay length in order to characterize hydrophobicity-induced bead-bead attractive interactions in polymer chains. J Mol Model 2010; 17:1911-8. [PMID: 21110052 DOI: 10.1007/s00894-010-0899-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 11/09/2010] [Indexed: 11/24/2022]
Abstract
In this paper, we quantitatively demonstrate that exponentially decaying attractive potentials can effectively mimic strong hydrophobic interactions between monomer units of a polymer chain dissolved in aqueous solvent. Classical approaches to modeling hydrophobic solvation interactions are based on invariant attractive length scales. However, we demonstrate here that the solvation interaction decay length may need to be posed as a function of the relative separation distances and the sizes of the interacting species (or beads or monomers) to replicate the necessary physical interactions. As an illustrative example, we derive a universal scaling relationship for a given solute-solvent combination between the solvation decay length, the bead radius, and the distance between the interacting beads. With our formalism, the hydrophobic component of the net attractive interaction between monomer units can be synergistically accounted for within the unified framework of a simple exponentially decaying potential law, where the characteristic decay length incorporates the distinctive and critical physical features of the underlying interaction. The present formalism, even in a mesoscopic computational framework, is capable of incorporating the essential physics of the appropriate solute-size dependence and solvent-interaction dependence in the hydrophobic force estimation, without explicitly resolving the underlying molecular level details.
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Affiliation(s)
- Siddhartha Das
- Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur 721302, India
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Vogel T, Neuhaus T, Bachmann M, Janke W. Ground-state properties of tubelike flexible polymers. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2009; 30:7-18. [PMID: 19777280 DOI: 10.1140/epje/i2009-10497-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2009] [Accepted: 07/15/2009] [Indexed: 05/28/2023]
Abstract
In this work we investigate the structural properties of native states of a simple model for short flexible homopolymers, where the steric influence of monomeric side chains is effectively introduced by a thickness constraint. This geometric constraint is implemented through the concept of the global radius of curvature and affects the conformational topology of ground-state structures. A systematic analysis allows for a thickness-dependent classification of the dominant ground-state topologies. It turns out that helical structures, strands, rings, and coils are natural, intrinsic geometries of such tubelike objects.
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Affiliation(s)
- T Vogel
- Institut für Theoretische Physik and Centre for Theoretical Sciences (NTZ), Universität Leipzig, Postfach 100 920, 04009 Leipzig, Germany.
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Nguyen TD, Glotzer SC. Switchable helical structures formed by the hierarchical self-assembly of laterally tethered nanorods. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2009; 5:2092-2098. [PMID: 19479922 DOI: 10.1002/smll.200900168] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The formation of helical scrolls formed by self-assembly of tethered nanorod amphiphiles and their molecular analogs are investigated. A model bilayer sheet assembled by laterally tethered nanorods is simulated and shown that it can fold into distinct helical morphologies under different solvent conditions. The helices can reversibly transform from one morphology to another by dynamically changing the solvent condition. This model serves both to inspire the fabrication of laterally tethered nanorods for assembling helices at nanometer scales and as a proof-of-concept for engineering switchable nanomaterials via hierarchical self-assembly.
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Affiliation(s)
- Trung Dac Nguyen
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
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Vogel T, Neuhaus T, Bachmann M, Janke W. Thermodynamics of tubelike flexible polymers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:011802. [PMID: 19658721 DOI: 10.1103/physreve.80.011802] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Indexed: 05/28/2023]
Abstract
In this work, we discuss the general phase behavior of short tubelike flexible polymers. The geometric thickness constraint is implemented through the concept of the global radius of curvature. We use sophisticated Monte Carlo sampling methods to simulate small bead-stick polymer models with Lennard-Jones interaction among nonbonded monomers. We analyze energetic fluctuations and structural quantities to classify conformational pseudophases. We find that the tube thickness influences the thermodynamic behavior of simple tubelike polymers significantly, i.e., for a given temperature, the formation of secondary structures strongly depends on the tube thickness.
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Affiliation(s)
- Thomas Vogel
- Institut für Theoretische Physik and Centre for Theoretical Sciences (NTZ), Universität Leipzig, Postfach 100 920, 04009 Leipzig, Germany
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