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Xu Y, Gilbert EP, Sokolova A, Stokes JR. Phase transition and gelation in cellulose nanocrystal-based aqueous suspensions studied by SANS. J Colloid Interface Sci 2024; 658:660-670. [PMID: 38134674 DOI: 10.1016/j.jcis.2023.12.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 12/01/2023] [Accepted: 12/07/2023] [Indexed: 12/24/2023]
Abstract
HYPOTHESIS Aqueous suspensions of cellulose nanocrystals (CNC) form a re-entrant liquid crystal (LC) phase with increasing salinity. Phase separation occurs in this LC state leading to a biphasic gel with a flow programmable structure that can be used to form anisotropic soft materials. We term this state a Liquid Crystal Hydroglass (LCH). Defining the mechanisms by which the LCH forms requires detailed structural analysis at the mesoscopic length scale. EXPERIMENTS By utilising Small Angle Neutron Scattering (SANS), we investigated the microstructure transitions in CNC suspensions, with a particular focus on the unique LC re-entrancy and gelation into the biphasic LCH. FINDINGS Scattering from LCH gels comprises contributions from a dispersed liquid state and static heterogeneity, characterised using a Lorentzian-Gaussian model of inhomogeneity. This conceptually supports a gelation mechanism (spinodal decomposition) in CNC suspensions towards a biphasic structure of the LCH. It also demonstrates that, with increasing salinity, the non-monotonic variation in effective volume fraction of CNC rods fundamentally causes the LC re-entrancy. This work provides the first experimental characterisation of the LC-re-entrancy and formation of an anisotropic LCH gel. The proposed mechanism can be extended to understanding the general behaviour of anisotropic colloids.
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Affiliation(s)
- Yuan Xu
- School of Chemical Engineering, The University of Queensland, Queensland, 4072, Australia.
| | - Elliot P Gilbert
- Australian Centre for Neutron Scattering, ANSTO, Lucas Heights, New South Wales, 2234, Australia
| | - Anna Sokolova
- Australian Centre for Neutron Scattering, ANSTO, Lucas Heights, New South Wales, 2234, Australia
| | - Jason R Stokes
- School of Chemical Engineering, The University of Queensland, Queensland, 4072, Australia.
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2
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Shimada R, Urakawa O, Inoue T, Watanabe H. Phase equilibrium and dielectric relaxation in mixture of 5CB with dilute dimethyl phthalate: effect of coupling between orientation and composition fluctuations on molecular dynamics in isotropic one-phase state. SOFT MATTER 2021; 17:6259-6272. [PMID: 34124720 DOI: 10.1039/d1sm00496d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Phase equilibrium and dielectric relaxation were examined for mixtures of liquid-crystalline (LC)-forming 4-cyano-4'-pentylbiphenyl (5CB) with dilute dimethyl phthalate (DMP). The mixtures were in an isotropic one-phase state at high temperatures T but were separated into nematic and isotropic phases at low T < TIN (isotropic-to-nematic transition temperature), and the isotropic phase disappeared and a nematic one-phase state was realized on a further decrease of T below another transition temperature . These TIN and data (phase diagram) were described considerably well by a simple model of free energy contributed from a Flory-Huggins type mixing entropy (no enthalpic contribution) and a Landau-de Gennes type nematic interaction. This success of the model, not expected for ordinary (not LC-forming) components exhibiting enthalpically-driven phase separation, suggested that the phase separation in the DMP/5CB mixtures was triggered by the nematic transition of 5CB (possibly governed by the packing entropy) and thus the orientation fluctuation of 5CB molecules was coupled with the composition fluctuation. This coupling was expected to affect the dielectric relaxation detecting the rotational dynamics of 5CB molecules, the major component in the mixtures. This expectation was examined for a representative mixture having the DMP content of wDMP = 3.1 wt% and TIN ≅ 27.0 °C. In a high-T asymptote (T > TIN + 10 °C), the dielectric relaxation of this mixture was close to that of pure 5CB, which suggested no significant effect of the above coupling on 5CB dynamics in the mixture at such high T. Nevertheless, in a significantly wide range of T between TIN and TIN + 10 °C, the dielectric relaxation time τε of the isotropic one-phase mixture increased on cooling much more significantly compared to τε in that high-T asymptote. The kinematic viscosity ν of the mixture exhibited a qualitatively similar increase in the same range of T, but this increase was weaker than that of τε. This difference between the dielectric τε and the rheological ν was attributed to coupling of the orientation and the composition fluctuations mentioned above. Namely, the composition fluctuation enhances the orientation fluctuation in the mixture thereby providing τε (reflecting the orientation fluctuation) with an extra increase. Pure 5CB exhibited similar increases of τε and ν (stronger for the former) but only in a close vicinity of (within 2-3 °C), because the orientation fluctuation in pure 5CB is coupled with the density fluctuation, not with the composition fluctuation being absent in the pure 5CB system. This behavior of pure 5CB in turn suggests an importance of the coupling of orientation and composition fluctuations in the mixture.
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Affiliation(s)
- Ryoko Shimada
- Department of Mathematical and Physical Sciences, Japan Women's University, Bunkyo-ku, Tokyo 112-8681, Japan.
| | - Osamu Urakawa
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560-0041, Japan.
| | - Tadashi Inoue
- Department of Macromolecular Science, Faculty of Science, Osaka University, Toyonaka, Osaka 560-0041, Japan.
| | - Hiroshi Watanabe
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
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Reyes CG, Baller J, Araki T, Lagerwall JPF. Isotropic-isotropic phase separation and spinodal decomposition in liquid crystal-solvent mixtures. SOFT MATTER 2019; 15:6044-6054. [PMID: 31225565 DOI: 10.1039/c9sm00921c] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Phase separation in mixtures forming liquid crystal (LC) phases is an important yet under-appreciated phenomenon that can drastically influence the behaviour of a multi-component LC. Here we demonstrate, using polarising microscopy with active cooling as well as differential scanning calorimetry, that the phase diagram for mixtures of the LC-forming compound 4'-n-pentylbiphenyl-4-carbonitrile (5CB) with ethanol is surprisingly complex. Binary mixtures reveal a broad miscibility gap that leads to phase separation between two distinct isotropic phases via spinodal decomposition or nucleation and growth. On further cooling the nematic phase enters on the 5CB-rich side, adding to the complexity. Significantly, water contamination dramatically raises the temperature range of the miscibility gap, bringing up the critical temperature for spinodal decomposition from ∼ 2 °C for the anhydrous case to >50 °C if just 3 vol% water is added to the ethanol. We support the experiments with a theoretical treatment that qualitatively reproduces the phase diagrams as well as the transition dynamics, with and without water. Our study highlights the impact of phase separation in LC-forming mixtures, spanning from equilibrium coexistence of multiple liquid phases to non-equilibrium effects due to persistent spatial concentration gradients.
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Affiliation(s)
- Catherine G Reyes
- Physics and Materials Science Research Unit, University of Luxembourg, 162a, Avenue de la Faencerie, L-1511, Luxembourg.
| | - Jörg Baller
- Physics and Materials Science Research Unit, University of Luxembourg, 162a, Avenue de la Faencerie, L-1511, Luxembourg.
| | - Takeaki Araki
- Department of Physics, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
| | - Jan P F Lagerwall
- Physics and Materials Science Research Unit, University of Luxembourg, 162a, Avenue de la Faencerie, L-1511, Luxembourg.
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Structure and rheology of liquid crystal hydroglass formed in aqueous nanocrystalline cellulose suspensions. J Colloid Interface Sci 2019; 555:702-713. [PMID: 31416025 DOI: 10.1016/j.jcis.2019.08.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 08/06/2019] [Accepted: 08/07/2019] [Indexed: 01/12/2023]
Abstract
HYPOTHESIS Liquid crystal hydroglass (LCH) is a biphasic soft material with flow programmable anisotropy that forms via phase separation in suspensions of charged colloidal rods upon increases in ionic strength. The unique structure and rheology of the LCH gel formed using nanocrystalline cellulose (NCC) is hypothesised to be dependent on colloidal stability that is modulated using specific ion effects arising from Hofmeister phenomena. EXPERIMENTS LCHs are prepared in NCC suspensions in aqueous media containing varying levels of sodium chloride (NaCl) or sodium thiocyanate (NaSCN). The NCC suspensions are characterised using rheology and structural analysis techniques that includes polarised optical microscopy, zeta potential, dynamic light scattering and small-angle X-ray scattering. FINDINGS The two salts have a profound effect on the formation process and structure of the LCH. Differences in network density and size of the liquid crystal domains are observed within the LCH for each of the salts, which is associated with the strength of interaction between NCC particles during LCH formation. In comparison to Cl- at the same salinity, the chaotropic nature of the weakly hydrated SCN- enhances colloidal stability by rendering NCC particles more hydrated and repulsive, but this also leads to weaker gel strength of the LCH. The results suggest that salts are a means in which to control the formation, structure and rheology of these anisotropic soft materials.
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Mao S, Kuldinow D, Haataja MP, Košmrlj A. Phase behavior and morphology of multicomponent liquid mixtures. SOFT MATTER 2019; 15:1297-1311. [PMID: 30506078 DOI: 10.1039/c8sm02045k] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Multicomponent systems are ubiquitous in nature and industry. While the physics of few-component liquid mixtures (i.e., binary and ternary ones) is well-understood and routinely taught in undergraduate courses, the thermodynamic and kinetic properties of N-component mixtures with N > 3 have remained relatively unexplored. An example of such a mixture is provided by the intracellular fluid, in which protein-rich droplets phase separate into distinct membraneless organelles. In this work, we investigate equilibrium phase behavior and morphology of N-component liquid mixtures within the Flory-Huggins theory of regular solutions. In order to determine the number of coexisting phases and their compositions, we developed a new algorithm for constructing complete phase diagrams, based on numerical convexification of the discretized free energy landscape. Together with a Cahn-Hilliard approach for kinetics, we employ this method to study mixtures with N = 4 and 5 components. We report on both the coarsening behavior of such systems, as well as the resulting morphologies in three spatial dimensions. We discuss how the number of coexisting phases and their compositions can be extracted with Principal Component Analysis (PCA) and K-means clustering algorithms. Finally, we discuss how one can reverse engineer the interaction parameters and volume fractions of components in order to achieve a range of desired packing structures, such as nested "Russian dolls" and encapsulated Janus droplets.
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Affiliation(s)
- Sheng Mao
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA
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Xu Y, Atrens AD, Stokes JR. "Liquid, gel and soft glass" phase transitions and rheology of nanocrystalline cellulose suspensions as a function of concentration and salinity. SOFT MATTER 2018; 14:1953-1963. [PMID: 29479584 DOI: 10.1039/c7sm02470c] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The colloidal size and rod morphology of nanocrystalline cellulose (NCC) lead to suspensions with useful phase and gelation behaviours as well as complex rheologies. However, these have not been comprehensively evaluated previously. Here we report the detailed phase behaviour of sulphonated NCC aqueous suspensions as a function of concentration and salinity. Four phases - liquid, viscoelastic, repulsive glass and attractive glass/gel - are identified in terms of their distinct rheological behaviours. The liquid-solid transitions (LSTs) are determined rheologically, and these are supported by a simplified model based on the DLVO theory that indicates the importance of charge in determining the phase behaviour. Rheology is also used to investigate the solid-solid transition from a repulsive glass to an attractive gel with increasing salt at high NCC concentrations. A time-dependent aging phenomenon is observed in suspensions with a composition just below the LSTs, and the implications of this on the dynamics occurring during gelation processes are discussed. This work can be directly applied to the development of structure-function relationships and the expanding utilisation of NCC suspensions, whilst also providing a basis for the study of charged colloidal rods more generally and evaluation of theoretical models.
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Affiliation(s)
- Yuan Xu
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
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Gruhn T, Pogorelov E, Seiferling F, Emmerich H. Analyzing spinodal decomposition of an anisotropic fluid mixture. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:055103. [PMID: 27941222 DOI: 10.1088/1361-648x/aa4de0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Spinodal decomposition leads to spontaneous fluctuations of the local concentration. In the early stage, the resulting pattern provides explicit information about the material properties of the mixture. In the case of two isotropic fluids, the static structure factor shows the characteristic ring shape. If one component is a liquid crystal, the pattern is typically anisotropic and the structure factor is more complex. Using numerical methods, we investigate how structure factors can be used to extract information about material properties like the diffusion constant or the isotropic and the anisotropic contributions to the interfacial tension. The method is based on momenta taken from structure factors in the early stage of the spinodal demixing. We perform phase field calculations for an isotropic and an anisotropic spinodal decomposition. A comparison of the extracted results with analytic values is made. The calculations show that linear modes dominate in the beginning of the growth process, while non-linear modes grow monotonously in the region of the k-space for which damping is predicted by the linearized theory. As long as non-linear modes are small enough, linearized theory can be applied to extract material properties from the structure factor.
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Affiliation(s)
- Thomas Gruhn
- Materials and Process Simulation (MPS), University of Bayreuth, Germany
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8
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Mkhonta SK, Elder KR, Huang ZF, Grant M. Microphase separation in comblike liquid-crystalline diblock copolymers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 88:042602. [PMID: 24229201 DOI: 10.1103/physreve.88.042602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Revised: 07/30/2013] [Indexed: 06/02/2023]
Abstract
The interplay between liquid crystallinity and microphase separation in comblike liquid-crystalline diblock copolymers is examined via a Brazovskii-type phenomenological model using both analytical and numerical calculations. For symmetric diblock copolymers we determine a critical electric field that is required to tilt the orientation of the constituent liquid crystals of the polymer side chains in the microphase-separated lamellar state. Such electrically induced reorientation of the liquid-crystal molecules can lead to substantially large changes of lamellar periodicity. Our numerical results show that highly aligned polymer lamellar domains can self-assemble when the liquid-crystal ordering precedes microphase separation, and that weak electric fields can be used to direct the self-assembly process due to the dielectric anisotropy of the liquid-crystal side chains. We also find that phase separation of asymmetric diblock copolymers can coexist with a network of liquid-crystal nematic orientations, with domain morphology depending on the details of copolymer and liquid-crystal coupling.
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Affiliation(s)
- S K Mkhonta
- Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48201, USA and Department of Physics, University of Swaziland, Private Bag 4, Kwaluseni M201, Swaziland
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10
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Matsuyama A. Phase separations in mixtures of a liquid crystal and a nanocolloidal particle. J Chem Phys 2010; 131:204904. [PMID: 19947706 DOI: 10.1063/1.3266509] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a mean field theory to describe phase separations in mixtures of a liquid crystal and a nanocolloidal particle. By taking into account a nematic, a smectic A ordering of the liquid crystal, and a crystalline ordering of the nanoparticle, we calculate the phase diagrams on the temperature-concentration plane. We predict various phase separations, such as a smectic A-crystal phase separation and a smectic A-isotropic-crystal triple point, etc., depending on the interactions between the liquid crystal and the colloidal surface. Inside binodal curves, we find new unstable and metastable regions, which are important in the phase ordering dynamics. We also find a crystalline ordering of the nanoparticles dispersed in a smectic A phase and a nematic phase. The cooperative phenomena between liquid-crystalline ordering and crystalline ordering induce a variety of phase diagrams.
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Affiliation(s)
- Akihiko Matsuyama
- Department of Bioscience and Bioinformatics, Faculty of Computer Science and System Engineering, Kyushu Institute of Technology, Kawazu 680-4, Iizuka, Fukuoka 820-8502, Japan.
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11
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An Energetic Variational Formulation with Phase Field Methods for Interfacial Dynamics of Complex Fluids: Advantages and Challenges. MODELING OF SOFT MATTER 2008. [DOI: 10.1007/0-387-32153-5_1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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12
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Matsuyama A. Morphology of spinodal decompositions in liquid crystal–colloid mixtures. J Chem Phys 2008; 128:224907. [DOI: 10.1063/1.2936831] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Matsuyama A, Hirashima R. Phase separations in liquid crystal-colloid mixtures. J Chem Phys 2008; 128:044907. [DOI: 10.1063/1.2823737] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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14
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Takenaka M, Shimizu H, Nishitsuji S, Hasegawa H. Concentration Fluctuations Induced by Orientation Fluctuations in Polymer−Liquid Crystal Mixture. Macromolecules 2006. [DOI: 10.1021/ma061427e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mikihito Takenaka
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Hirofumi Shimizu
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Shotaro Nishitsuji
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Hirokazu Hasegawa
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
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15
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Das SK, Rey AD. Magnetic Field-Induced Shape Transitions in Multiphase Polymer-Liquid Crystal Blends. MACROMOL THEOR SIMUL 2006. [DOI: 10.1002/mats.200600024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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16
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Kihara H, Miura T. Morphology of a hydrogen-bonded LC polymer prepared by photopolymerization-induced phase separation under an isotropic phase. POLYMER 2005. [DOI: 10.1016/j.polymer.2005.08.068] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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17
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Das SK, Rey AD. Kinetic structures in multi-phase liquid-crystalline composite materials. MOLECULAR SIMULATION 2005. [DOI: 10.1080/08927020412331332613] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Das SK, Rey AD. Texture formation under phase ordering and phase separation in polymer-liquid crystal mixtures. J Chem Phys 2004; 121:9733-43. [PMID: 15538897 DOI: 10.1063/1.1804494] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Computational modeling of texture formation in coupled phase separation-phase ordering processes in polymer/liquid crystal mixtures is performed using a unified model based on the nematic tensor order parameter and gradient orientation elasticity. The computational methods are able to resolve defect nucleation, defect-defect interactions, and defect-particle interactions, as well as global and local morphological features in the concentration and order parameter spatiotemporal behavior. Biphasic structures corresponding to polymer dispersed liquid crystals (PDLCs), crystalline filled nematic (CFNs), and random filled nematics (RFNs) are captured and analyzed using liquid crystal defect physics and structure factors. Under spinodal decomposition due to concentration fluctuations, the PDLC structure emerges, and the nucleation and repulsive interaction of defects within nematic droplets leads to bipolar nematic droplets. Under spinodal decomposition due to ordering fluctuations, the CFNs structure emerges, and the stable polymer droplet crystal is pinned by a lattice of topological defects. For intermediate cases, where the mixture is unstable to both concentration and nematic order fluctuations, the RFN structure emerges, and polymer droplets and fibrils are pinned by a defect network, whose density increases with the curvature of the polymer-liquid crystal interface. The simulations provide an information of the role of topological defects on phase separation-phase ordering processes in polymer-liquid crystal mixtures.
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Affiliation(s)
- Susanta K Das
- Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec, H3A 2B2 Canada
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Rey AD, Grecov D, Das SK. Thermodynamic and Flow Modeling of Meso- and Macrotextures in Polymer−Liquid Crystal Material Systems. Ind Eng Chem Res 2004. [DOI: 10.1021/ie030855v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alejandro D. Rey
- Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec, Canada H3A 2B2
| | - Dana Grecov
- Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec, Canada H3A 2B2
| | - Susanta K. Das
- Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, Quebec, Canada H3A 2B2
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20
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Spakowitz AJ, Wang ZG. Semiflexible polymer solutions. I. Phase behavior and single-chain statistics. J Chem Phys 2003. [DOI: 10.1063/1.1628669] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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21
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Graca M, Wieczorek SA, Hołyst R. Growth of Polystyrene Domains in Isotropic, Nematic and Smectic Phase of 8CB Liquid Crystal. Macromolecules 2003. [DOI: 10.1021/ma034135b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- M. Graca
- Institute of Physical Chemistry PAS, Department III, Kasprzaka 44/52, 01-224 Warsaw, Poland, and WMP-SNS, Cardinal Stefan Wyszyṅski University, Dewajtis 5, Warsaw, Poland
| | - S. A. Wieczorek
- Institute of Physical Chemistry PAS, Department III, Kasprzaka 44/52, 01-224 Warsaw, Poland, and WMP-SNS, Cardinal Stefan Wyszyṅski University, Dewajtis 5, Warsaw, Poland
| | - R. Hołyst
- Institute of Physical Chemistry PAS, Department III, Kasprzaka 44/52, 01-224 Warsaw, Poland, and WMP-SNS, Cardinal Stefan Wyszyṅski University, Dewajtis 5, Warsaw, Poland
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22
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Hamm M, Goldbeck-Wood G, Zvelindovsky AV, Fraaije JGEM. Microstructure of nematic amorphous block copolymers: Dependence on the nematic volume fraction. J Chem Phys 2003. [DOI: 10.1063/1.1568332] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Graca M, Wieczorek SA, Hołyst R. Polymer domain growth in ordered liquid crystalline matrices. PHYSICAL REVIEW LETTERS 2003; 90:115504. [PMID: 12688941 DOI: 10.1103/physrevlett.90.115504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2002] [Indexed: 05/24/2023]
Abstract
The growth of polymer domains in the isotropic, nematic, and smectic matrices is studied by the light scattering. In the smectic and isotropic matrices the growth is diffusive, and in the nematic matrix it is influenced by the elastic forces. The scaling is obeyed. A crossover to the wetting fast-mode hydrodynamic regime is also observed at long times. In order to perform these measurements we had to eliminate the multiple scattering of light.
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Affiliation(s)
- M Graca
- Institute of Physical Chemistry, Polish Academy of Science, Department III, Kasprzaka 44/52, 01224 Warsaw, Poland
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Hong K, Zhang H, Yang Y. The external electric field effects on the morphology of phase separation in a mixture of liquid crystal/flexible polymer. J Appl Polym Sci 2002. [DOI: 10.1002/app.10956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Voloschenko D, Pishnyak OP, Shiyanovskii SV, Lavrentovich OD. Effect of director distortions on morphologies of phase separation in liquid crystals. PHYSICAL REVIEW E 2002; 65:060701. [PMID: 12188694 DOI: 10.1103/physreve.65.060701] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2001] [Indexed: 11/07/2022]
Abstract
We study phase separation from a nematic liquid crystal with spatially nonuniform director gradients. Particles of a phase-separated component, which is either an isotropic fluid (silicone oil) or a nonmesogenic photopolymer, accumulate in the regions with the strongest director distortions, thus reducing the overall energy of the system.
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Affiliation(s)
- D Voloschenko
- Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
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26
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Muratov CB, E W. Theory of phase separation kinetics in polymer–liquid crystal systems. J Chem Phys 2002. [DOI: 10.1063/1.1426411] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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27
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Hamm M, Goldbeck-Wood G, Zvelindovsky AV, Sevink GJA, Fraaije JGEM. Structure formation in liquid crystalline polymers. J Chem Phys 2002. [DOI: 10.1063/1.1436117] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kyu T, Nwabunma D. Simulations of Microlens Arrays Formed by Pattern-Photopolymerization-Induced Phase Separation of Liquid Crystal/Monomer Mixtures. Macromolecules 2001. [DOI: 10.1021/ma010567f] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Thein Kyu
- Institute of Polymer Engineering, The University of Akron, Akron, Ohio 44325-0301
| | - Domasius Nwabunma
- Institute of Polymer Engineering, The University of Akron, Akron, Ohio 44325-0301
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Kyu T, Chiu HW. Morphology development during polymerization-induced phase separation in a polymer dispersed liquid crystal. POLYMER 2001. [DOI: 10.1016/s0032-3861(01)00389-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Kyu T, Nwabunma D, Chiu HW. Theoretical simulation of holographic polymer-dispersed liquid-crystal films via pattern photopolymerization-induced phase separation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 63:061802. [PMID: 11415131 DOI: 10.1103/physreve.63.061802] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2000] [Indexed: 05/06/2023]
Abstract
A theoretical simulation has been performed to elucidate the emergence of nematic domains during pattern photopolymerization-induced phase separation in holographic polymer-dispersed liquid crystals. We consider a reference system consisting of a single-component nematic, namely, 4-n-heptyl-4(')-cyanobiphenyl (T(NI)=42 degrees C), and a polymer network made from multifunctional monomers. To mimic pattern photopolymerization, the reaction rate was varied periodically in space through wave mixing. In the theoretical development, the photopolymerization kinetics was coupled with the time-dependent Ginzburg-Landau model C equations by incorporating the local free energy densities pertaining to isotropic liquid-liquid mixing, nematic ordering, and network elasticity. The simulated morphological patterns in the concentration and orientation order parameter fields show discrete layers of liquid-crystal droplets alternating periodically with polymer-network-rich layers. The Fourier transforms of these patterns show sharp diffraction spots arising from the periodic layers. As the layer thickness is reduced, the liquid-crystal molecules are confined in the narrow stripes. The liquid-crystal domains appear uniform along the stripes, which in turn gives rise to sharper diffraction spots in Fourier space. Of particular interest is that our simulated stratified patterns are in qualitative agreement with reported experimental observations.
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Affiliation(s)
- T Kyu
- Institute of Polymer Engineering, The University of Akron, Akron, Ohio 44325, USA.
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Ma Y. Wetting-driven structure formation of a binary mixture in the presence of a mobile particle pinning potential. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 62:8207-11. [PMID: 11138119 DOI: 10.1103/physreve.62.8207] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2000] [Indexed: 11/07/2022]
Abstract
We investigate the pattern formation on the solid substrate of phase-separating films containing mobile wetting particles with a preferential attraction for one component of the mixtures. The presence of mobile particles under the surface-particle interaction modulation breaks the isotropy of the bulk phase-separating process, leading to the formation of orientational structure due to the interplay between phase separation and wetting particle ordering under a modulated pinning potential at the late stage. Simulations suggest that the phase-separation morphology can be changed through the adjustment of the wettable-phase-particle interaction and the surface-particle interaction. It provides some important insights into this "wetting-directed spinodal decomposition."
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Affiliation(s)
- Yq Ma
- National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
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Matsuyama A, Kato T. Early stages of spinodal decomposition in binary liquid crystal mixtures. J Chem Phys 2000. [DOI: 10.1063/1.1319656] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Nwabunma D, Chiu HW, Kyu T. Theoretical investigation on dynamics of photopolymerization-induced phase separation and morphology development in nematic liquid crystal/polymer mixtures. J Chem Phys 2000. [DOI: 10.1063/1.1309537] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Peng G, Qiu F, Ginzburg VV, Jasnow D, Balazs AC. Forming supramolecular networks from nanoscale rods in binary, phase-separating mixtures. Science 2000; 288:1802-4. [PMID: 10846157 DOI: 10.1126/science.288.5472.1802] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Simulations show that when low-volume fractions of nanoscale rods are immersed in a binary, phase-separating blend, the rods self-assemble into needle-like, percolating networks. The interconnected network arises through the dynamic interplay of phase-separation between the fluids, through preferential adsorption of the minority component onto the mobile rods, and through rod-rod repulsion. Such cooperative effects provide a means of manipulating the motion of nanoscopic objects and directing their association into supramolecular structures. Increasing the rod concentration beyond the effective percolation threshold drives the system to self-assemble into a lamellar morphology, with layers of wetted rods alternating with layers of the majority-component fluid. This approach can potentially yield organic/inorganic composites that are ordered on nanometer scales and exhibit electrical or structural integrity.
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Affiliation(s)
- G Peng
- Chemical Engineering Department and Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15261, USA
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