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Parisi D, Truzzolillo D, Slim AH, Dieudonné-George P, Narayanan S, Conrad JC, Deepak VD, Gauthier M, Vlassopoulos D. Gelation and Re-entrance in Mixtures of Soft Colloids and Linear Polymers of Equal Size. Macromolecules 2023; 56:1818-1827. [PMID: 36938509 PMCID: PMC10019458 DOI: 10.1021/acs.macromol.2c02491] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 02/02/2023] [Indexed: 02/24/2023]
Abstract
Liquid mixtures composed of colloidal particles and much smaller non-adsorbing linear homopolymers can undergo a gelation transition due to polymer-mediated depletion forces. We now show that the addition of linear polymers to suspensions of soft colloids having the same hydrodynamic size yields a liquid-to-gel-to-re-entrant liquid transition. In particular, the dynamic state diagram of 1,4-polybutadiene star-linear polymer mixtures was determined with the help of linear viscoelastic and small-angle X-ray scattering experiments. While keeping the star polymers below their nominal overlap concentration, a gel was formed upon increasing the linear polymer content. Further addition of linear chains yielded a re-entrant liquid. This unexpected behavior was rationalized by the interplay of three possible phenomena: (i) depletion interactions, driven by the size disparity between the stars and the polymer length scale which is the mesh size of its entanglement network; (ii) colloidal deswelling due to the increased osmotic pressure exerted onto the stars; and (iii) a concomitant progressive suppression of the depletion efficiency on increasing the polymer concentration due to reduced mesh size, hence a smaller range of attraction. Our results unveil an exciting new way to tailor the flow of soft colloids and highlight a largely unexplored path to engineer soft colloidal mixtures.
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Affiliation(s)
- Daniele Parisi
- FORTH,
Institute of Electronic Structure and Laser, Heraklion 70013, Crete, Greece
- Department
of Chemical Engineering, Product Technology, University of Groningen, Nijenborgh 4, Groningen 9747 AG, The Netherlands
| | - Domenico Truzzolillo
- Laboratoire
Charles Coulomb (L2C), UMR 5221 CNRS Université de Montpellier, Montpellier 34095, France
| | - Ali H. Slim
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | | | - Suresh Narayanan
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jacinta C. Conrad
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Vishnu D. Deepak
- Department
of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Mario Gauthier
- Department
of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Dimitris Vlassopoulos
- FORTH,
Institute of Electronic Structure and Laser, Heraklion 70013, Crete, Greece
- Department
of Materials Science and Technology, University
of Crete, Heraklion 70013, Crete, Greece
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Nickel AC, Denton AR, Houston JE, Schweins R, Plivelic TS, Richtering W, Scotti A. Beyond simple self-healing: How anisotropic nanogels adapt their shape to their environment. J Chem Phys 2022; 157:194901. [DOI: 10.1063/5.0119527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The response of soft colloids to crowding depends sensitively on the particles’ compressibility. Nanogel suspensions provide model systems that are often studied to better understand the properties of soft materials and complex fluids from the formation of colloidal crystals to the flow of viruses, blood, or platelet cells in the body. Large spherical nanogels, when embedded in a matrix of smaller nanogels, have the unique ability to spontaneously deswell to match their size to that of the nanogel composing the matrix. In contrast to hard colloids, this self-healing mechanism allows for crystal formation without giving rise to point defects or dislocations. Here, we show that anisotropic ellipsoidal nanogels adapt both their size and their shape depending on the nature of the particles composing the matrix in which they are embedded. Using small-angle neutron scattering with contrast variation, we show that ellipsoidal nanogels become spherical when embedded in a matrix of spherical nanogels. In contrast, the anisotropy of the ellipsoid is enhanced when they are embedded in a matrix of anisotropic nanogels. Our experimental data are supported by Monte Carlo simulations that reproduce the trend of decreasing aspect ratio of ellipsoidal nanogels with increasing crowding by a matrix of spherical nanogels.
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Affiliation(s)
- Anne C. Nickel
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - Alan R. Denton
- Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050, USA
| | | | - Ralf Schweins
- Institut Laue-Langevin ILL DS/LSS, 71 Avenue des Martyrs, F-38000 Grenoble, France
| | - Tomàs S. Plivelic
- MAX IV Laboratory, Lund University, P.O. Box 118, 22100 Lund, Sweden
| | - Walter Richtering
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
| | - Andrea Scotti
- Institute of Physical Chemistry, RWTH Aachen University, 52056 Aachen, Germany
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Parisi D, Seo J, Nazari B, Schaake RP, Rhoades AM, Colby RH. Shear-Induced Isotropic-Nematic Transition in Poly(ether ether ketone) Melts. ACS Macro Lett 2020; 9:950-956. [PMID: 35648606 DOI: 10.1021/acsmacrolett.0c00404] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In a previous work on a poly(ether ether ketone) (PEEK) melt, above its nominal melting temperature (Tm ≅ 335 °C), a severe Cox-Merz rule failure was observed. The abrupt decrease in the apparent shear viscosity was ascribed to the formation of flow-induced crystallization precursors. Here shear rheology and reflection polariscope experiments are utilized to unravel the structural changes occurring under shear on a similar PEEK melt above Tm. Three regimes of the flow curve were identified from low (0.01 s-1) to high shear rates (1000 s-1): (I) an isotropic structure with weak birefringence due to polymer chain orientation and mild shear thinning for γ̇ < 1 s-1, (II) an isotropic-nematic transition accompanied by strong birefringence, two steady-state viscosities, and large nematic polydomain director fluctuations, and (III) shear-thinning behavior with an η ∼ γ̇-0.5 dependence for γ̇ > 20 s-1, typically found in nematic fluids. The findings reported in this experimental work suggest that the nematic phase may represent the early stage of the formation of shear-induced crystallization precursors.
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Affiliation(s)
- Daniele Parisi
- Department of Materials Science and Engineering, Penn State University, University Park, Pennsylvania 16802, United States
| | - Jiho Seo
- Department of Materials Science and Engineering, Penn State University, University Park, Pennsylvania 16802, United States
| | - Behzad Nazari
- School of Engineering, Penn State Behrend, Erie, Pennsylvania 16563, United States
| | - Richard P Schaake
- SKF Research & Technology Development, 3992 AE Houten, The Netherlands
| | - Alicyn M Rhoades
- School of Engineering, Penn State Behrend, Erie, Pennsylvania 16563, United States
| | - Ralph H Colby
- Department of Materials Science and Engineering, Penn State University, University Park, Pennsylvania 16802, United States
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