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Kalapurakal RAM, Jha PK, Vashisth H. Theory and simulations of light-induced self-assembly in colloids with quantum chemistry derived empirical potentials. SOFT MATTER 2024. [PMID: 39086325 DOI: 10.1039/d4sm00459k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/02/2024]
Abstract
Light-induced self-assembly (LISA) is a non-invasive method for tuning material properties. Photoresponsive ligands coated on the surfaces of nanoparticles are often used to achieve LISA. We report simulation studies for a photoresponsive ligand, azobenzene dithiol (ADT), which switches from a trans-to-cis configuration on exposure to ultraviolet light, allowing self-assembly in ADT-coated gold nanoparticles (NPs). This is attributed to a higher dipole moment of cis-ADT over trans-ADT which leads to a dipole-dipole attraction facilitating self-assembly. Singh and Jha [Comput. Theor. Chem., 2021, 1206, 113492] used quantum-chemistry calculations to quantify the interaction energy of a pair of ADT ligands in their cis and trans conformations. The interaction energy between ligands was fit to a potential energy function of the Lennard-Jones (LJ) form having distinct exponents for attractive and repulsive contributions. Using this generalized equation for the ligand-ligand interaction energy, we calculated the total effective interaction energy between a pair of cis as well as trans ADT-coated NPs. Specifically, we calculated the effective interaction energies between cis/trans-NPs using discrete as well as continuous approaches. Given the limitations of experiments in probing individual ligand conformations, we also studied the effect of varying the functional ligand length on the interaction energy between NPs and identified the optimal functional ligand length to capture the steric and conformational effects. Finally, using the effective interaction energy, we obtained a generalized potential energy function, which was applied in Langevin dynamics simulations to capture self-assembly in NPs.
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Affiliation(s)
| | - Prateek K Jha
- Department of Chemical Engineering, Indian Institute of Technology, Roorkee 247667, India.
| | - Harish Vashisth
- Department of Chemical Engineering and Bioengineering, University of New Hampshire, Durham, NH 03824, USA.
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA
- Integrated Applied Mathematics Program, University of New Hampshire, Durham, NH 03824, USA
- Molecular and Cellular Biotechnology Program, University of New Hampshire, Durham, NH 03824, USA
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2
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Saphiannikova M, Toshchevikov V, Tverdokhleb N. Optical deformations of azobenzene polymers: orientation approach vs. other concepts. SOFT MATTER 2024; 20:2688-2710. [PMID: 38465418 DOI: 10.1039/d4sm00104d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
It has been 30 years since the discovery of surface restructuring in thin azopolymer films by two independent research groups. A wide variety of topographical structures have been created by the application of two-/four-beam interference patterns, space light modulators and even helical beams. There are a number of comprehensive reviews which describe in detail the advances in superficial photopatterning of azopolymer films and macroscopic deformations of azonetworks. The theoretical approaches are only briefly touched on in these reviews and often are accompanied by the remark that the phenomenon is far from being understood. In this review, we would like to present the polymer theoretist's point of view on this intriguing problem. We begin by describing a multitude of theoretical approaches and commenting on the pluses and drawbacks of each. Importantly, we show that in most cases the presence of an azopolymer matrix is either ignored or limited to a specific class of azopolymers (liquid-crystalline or elastomeric). We then move to early orientation approaches based on the hypothesis that reorientation of azo-chromophores by modulated polarized light is the sole cause of superficial patterning. At the end of the review a modern orientation approach, as proposed by our own group, is presented. This approach has high predictive power because it can explain a large pool of experimental data for different classes of azopolymers including glassy and liquid-crystalline materials. This is made possible by taking into account both the light-induced orientation process and the change of anisotropic interactions between the chromophores upon their isomerization. Last but not least, this is the only approach that provides an estimate of the light-induced stress large enough to cause plastic deformations of glassy azopolymers. Recent finite element modeling results show remarkable similarity to real patterns and even time-dependent data are well explained. With this, we claim that the puzzle is finally understood and the orientation approach is ready for its implementation for major azopolymer classes.
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Affiliation(s)
- Marina Saphiannikova
- Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany.
| | - Vladimir Toshchevikov
- Institute of Macromolecular Compounds, Russian Academy of Sciences, 199004 Saint Petersburg, Russia
| | - Nina Tverdokhleb
- Institute Theory of Polymers, Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany.
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3
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Ning Y, Yang S, Yang DB, Cai YY, Xu J, Li R, Zhang Y, Kagan CR, Saven JG, Murray CB. Dynamic Nanocrystal Superlattices with Thermally Triggerable Lubricating Ligands. J Am Chem Soc 2024; 146:3785-3795. [PMID: 38295018 DOI: 10.1021/jacs.3c10706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
The size-dependent and collective physical properties of nanocrystals (NCs) and their self-assembled superlattices (SLs) enable the study of mesoscale phenomena and the design of metamaterials for a broad range of applications. However, the limited mobility of NC building blocks in dried NCSLs often hampers the potential for employing postdeposition methods to produce high-quality NCSLs. In this study, we present tailored promesogenic ligands that exhibit a lubricating property akin to thermotropic liquid crystals. The lubricating ability of ligands is thermally triggerable, allowing the dry solid NC aggregates deposited on the substrates with poor ordering to be transformed into NCSLs with high crystallinity and preferred orientations. The interplay between the dynamic behavior of NCSLs and the molecular structure of the ligands is elucidated through a comprehensive analysis of their lubricating efficacy using both experimental and simulation approaches. Coarse-grained molecular dynamic modeling suggests that a shielding layer from mesogens prevents the interdigitation of ligand tails, facilitating the sliding between outer shells and consequently enhancing the mobility of NC building blocks. The dynamic organization of NCSLs can also be triggered with high spatial resolution by laser illumination. The principles, kinetics, and utility of lubricating ligands could be generalized to unlock stimuli-responsive metamaterials from NCSLs and contribute to the fabrication of NCSLs.
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Krishnamurthy S, Mathews Kalapurakal RA, Mani E. Computer simulations of self-assembly of anisotropic colloids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:273001. [PMID: 35172296 DOI: 10.1088/1361-648x/ac55d6] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 02/16/2022] [Indexed: 06/14/2023]
Abstract
Computer simulations have played a significant role in understanding the physics of colloidal self-assembly, interpreting experimental observations, and predicting novel mesoscopic and crystalline structures. Recent advances in computer simulations of colloidal self-assembly driven by anisotropic or orientation-dependent inter-particle interactions are highlighted in this review. These interactions are broadly classified into two classes: entropic and enthalpic interactions. They mainly arise due to shape anisotropy, surface heterogeneity, compositional heterogeneity, external field, interfaces, and confinements. Key challenges and opportunities in the field are discussed.
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Affiliation(s)
- Sriram Krishnamurthy
- Polymer Engineering and Colloids Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
| | - Remya Ann Mathews Kalapurakal
- Polymer Engineering and Colloids Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
| | - Ethayaraja Mani
- Polymer Engineering and Colloids Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
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5
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Dissipative morphological characteristics of photo-responsive block copolymers driven by time-oscillatory irradiations: An in silico study. POLYMER 2021. [DOI: 10.1016/j.polymer.2021.124234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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6
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Pesce L, Perego C, Grommet AB, Klajn R, Pavan GM. Molecular Factors Controlling the Isomerization of Azobenzenes in the Cavity of a Flexible Coordination Cage. J Am Chem Soc 2020; 142:9792-9802. [PMID: 32353237 PMCID: PMC7644116 DOI: 10.1021/jacs.0c03444] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
Photoswitchable
molecules are employed for many applications, from
the development of active materials to the design of stimuli-responsive
molecular systems and light-powered molecular machines. To fully exploit
their potential, we must learn ways to control the mechanism and kinetics
of their photoinduced isomerization. One possible strategy involves
confinement of photoresponsive switches such as azobenzenes or spiropyrans
within crowded molecular environments, which may allow control over
their light-induced conversion. However, the molecular factors that
influence and control the switching process under realistic conditions
and within dynamic molecular regimes often remain difficult to ascertain.
As a case study, here we have employed molecular models to probe the
isomerization of azobenzene guests within a Pd(II)-based coordination
cage host in water. Atomistic molecular dynamics and metadynamics
simulations allow us to characterize the flexibility of the cage in
the solvent, the (rare) guest encapsulation and release events, and
the relative probability/kinetics of light-induced isomerization of
azobenzene analogues in these host–guest systems. In this way,
we can reconstruct the mechanism of azobenzene switching inside the
cage cavity and explore key molecular factors that may control this
event. We obtain a molecular-level insight on the effects of crowding
and host–guest interactions on azobenzene isomerization. The
detailed picture elucidated by this study may enable the rational
design of photoswitchable systems whose reactivity can be controlled
via host–guest interactions.
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Affiliation(s)
- Luca Pesce
- Department of Innovative Technologies, University of Applied Sciences and Arts of Southern Switzerland, Galleria 2, Via Cantonale 2c, CH-6928 Manno, Switzerland
| | - Claudio Perego
- Department of Innovative Technologies, University of Applied Sciences and Arts of Southern Switzerland, Galleria 2, Via Cantonale 2c, CH-6928 Manno, Switzerland
| | - Angela B Grommet
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Rafal Klajn
- Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Giovanni M Pavan
- Department of Innovative Technologies, University of Applied Sciences and Arts of Southern Switzerland, Galleria 2, Via Cantonale 2c, CH-6928 Manno, Switzerland.,Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin, Italy
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7
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Gavilán-Arriazu EM, Giménez RE, Pinto OA. Structural surface and thermodynamics analysis of nanoparticles with defects. Phys Chem Chem Phys 2020; 22:23148-23157. [DOI: 10.1039/d0cp03348k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work, we analyze the surface structure and thermodynamics regarding the decoration of nanoparticles with defects, using statistical calculations and Monte Carlo simulations in a complementary way.
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Affiliation(s)
- E. M. Gavilán-Arriazu
- Instituto de Bionanotecnología del NOA (INBIONATEC-CONICET)
- Universidad Nacional de Santiago de Estero
- Santiago del Estero
- Argentina
| | - Rodrigo E. Giménez
- Laboratorio de Biointerfases y Sistemas Biomiméticos, Centro de Investigaciones en Biofisica Aplicada y Alimentos (CIBAAL) (UNSE-CONICET), Villa el Zanjón
- Argentina
| | - O. A. Pinto
- Instituto de Bionanotecnología del NOA (INBIONATEC-CONICET)
- Universidad Nacional de Santiago de Estero
- Santiago del Estero
- Argentina
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8
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Ilnytskyi JM, Toshchevikov V, Saphiannikova M. Modeling of the photo-induced stress in azobenzene polymers by combining theory and computer simulations. SOFT MATTER 2019; 15:9894-9908. [PMID: 31774109 DOI: 10.1039/c9sm01853k] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
It has been shown recently that the photo-induced deformations in azobenzene-containing polymers of a side-chain architecture can be explained by means of the so-called orientational approach. The explanation is based on the following sequence of steps: (i) reorientation of azobenzenes under illumination, (ii) reorientation of the polymer backbones coupled mechanically to azobenzenes, and (iii) development of large stress in a material. Step (i) is based on the angle selective absorption of the azobenzene chromophore, which is a well established fact. Step (iii) has been validated in a series of recent theoretic studies in an infinite coupling limit. Concerning step (ii), in a real material, the backbone-azobenzene coupling will be always finite, resulting in a decrease of the effective torque sensed by the backbones and in a time delay in their reorientation. To study the relevance of these effects in detail, we perform coarse-grained molecular dynamics simulations of side-chain azobenzene-containing oligomers in bulk at conditions close to the glassy state. The focus is on the dynamical properties of such a system and on its response to the illumination, with the latter modeled either as an orientation potential applied to the azobenzenes or via their stochastic photo-isomerization. By matching the amount of light-induced stress evaluated in both cases, we obtained the equivalent orientation potential as a function of the illumination intensity and the system density.
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Affiliation(s)
- Jaroslav M Ilnytskyi
- Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1, Svientsitskii Str., 79011 Lviv, Ukraine.
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10
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Bochicchio D, Kwangmettatam S, Kudernac T, Pavan GM. How Defects Control the Out-of-Equilibrium Dissipative Evolution of a Supramolecular Tubule. ACS NANO 2019; 13:4322-4334. [PMID: 30875196 DOI: 10.1021/acsnano.8b09523] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Supramolecular architectures that work out-of-equilibrium or that can change in specific ways when absorbing external energy are ubiquitous in nature. Gaining the ability to create via self-assembly artificial materials possessing such fascinating behaviors would have a major impact in many fields. However, the rational design of similar dynamic structures requires to understand and, even more challenging, to learn how to master the molecular mechanisms governing how the assembled systems evolve far from the equilibrium. Typically, this represents a daunting challenge due to the limited molecular insight that can be obtained by the experiments or by classical modeling approaches. Here we combine coarse-grained molecular models and advanced simulation approaches to study at submolecular (<5 Å) resolution a supramolecular tubule, which breaks and disassembles upon absorption of light energy triggering isomerization of its azobenzene-containing monomers. Our approach allows us to investigate the molecular mechanism of monomer transition in the assembly and to elucidate the kinetic process for the accumulation of the transitions in the system. Despite the stochastic nature of the excitation process, we demonstrate how these tubules preferentially dissipate the absorbed energy locally via the amplification of defects in their supramolecular structure. We find that this constitutes the best kinetic pathway for accumulating monomer transitions in the system, which determines the dynamic evolution out-of-equilibrium and the brittle behavior of the assembly under perturbed conditions. Thanks to the flexibility of our models, we finally come out with a general principle, where defects explain and control the brittle/soft behavior of such light-responsive assemblies.
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Affiliation(s)
- Davide Bochicchio
- Department of Innovative Technologies , University of Applied Sciences and Arts of Southern Switzerland , Galleria 2, Via Cantonale 2c , CH-6928 Manno , Switzerland
| | - Supaporn Kwangmettatam
- Molecular Nanofabrication Group, MESA+ Institute for Nanotechnology , University of Twente , PO Box 207, 7500 AE Enschede , The Netherlands
| | - Tibor Kudernac
- Molecular Nanofabrication Group, MESA+ Institute for Nanotechnology , University of Twente , PO Box 207, 7500 AE Enschede , The Netherlands
| | - Giovanni M Pavan
- Department of Innovative Technologies , University of Applied Sciences and Arts of Southern Switzerland , Galleria 2, Via Cantonale 2c , CH-6928 Manno , Switzerland
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11
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Borówko M, Rżysko W, Sokołowski S, Pizio O. Molecular dynamics and density functional study of the structure of hairy particles at a hard wall. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2017.11.146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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12
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Staszewski T, Borówko M. Molecular dynamics simulations of mono-tethered particles at solid surfaces. Phys Chem Chem Phys 2018; 20:20194-20204. [PMID: 30027950 DOI: 10.1039/c8cp03007c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We use molecular dynamics simulations to study the behavior of mono-tethered nanoparticles on solid surfaces. In our model particle-particle and particle-chain interactions are repulsive, while chain-chain interactions are attractive. Two surfaces are considered: the first one attracts particles and the other attracts chains. Excess adsorption isotherms are presented for both the surfaces and different lengths of tethers. The mechanism of adsorption is discussed. We find that depending on the assumed parameters the mono-tethered particles can be adsorbed as single particles or as different aggregates. Our main goal is to explore the structure of surface films. We show that the morphology of the adsorbed layer depends mainly on the type of the surface but the influence of the particle diameter, the chain length and the density is also important. We prove that the shape of aggregates changes near the substrate. For certain parameters the aggregates can break under the influence of the surface.
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Affiliation(s)
- Tomasz Staszewski
- Department for the Modelling of Physico-Chemical Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland.
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Ilnytskyi JM, Slyusarchuk A, Sokołowski S. Gelation of patchy ligand shell nanoparticles decorated by liquid-crystalline ligands: computer simulation study. SOFT MATTER 2018; 14:3799-3810. [PMID: 29717735 DOI: 10.1039/c8sm00356d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We consider the coarse-grained modelling of patchy ligand shell nanoparticles with liquid crystalline ligands. The cases of two, three, four and six symmetrically arranged patches of ligands are discussed, as well as the cases of their equatorial and icosahedral arrangement. A solution of decorated nanoparticles is considered within a slit-like pore with solid walls and the interior filled by a polar solvent. The ligands form physical cross-links between the nanoparticles due to strong liquid crystalline interaction, turning the solution into a gel-like structure. Gelation is carried out repeatedly starting each time from a freshly equilibrated dispersed state of nanoparticles. The gelation dynamics and the range of network characteristics of the gel are examined, depending on the type of patchy decoration and on the solution density. Emphasis is given to the theoretical prediction of the type of decoration and the solution density most suitable for producing a uniformly cross-linked and highly elastic gel structure.
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Affiliation(s)
- Jaroslav M Ilnytskyi
- Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1, Svientsitskii Str., 79011 Lviv, Ukraine.
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14
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Borówko M, Rżysko W, Sokołowski S, Staszewski T. Self-assembly of hairy disks in two dimensions - insights from molecular simulations. SOFT MATTER 2018; 14:3115-3126. [PMID: 29624197 DOI: 10.1039/c8sm00213d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report the results of large scale molecular dynamics simulations conducted for sparsely grafted disks in two-dimensional systems. The main goal of this work is to show how the ligand mobility influences the self-assembly of particles decorated with short chains. We also analyze the impact of the chain length on the structure of dense phases. A crossover between the systems controlled by the core-core or by the segment-segment interactions is discussed. We prove that the ligand mobility determines the structure of the system. The particles with fixed tethers are found to order into different structures, an amorphous phase, hexagonal or honeycomb lattices, and a "spaghetti"-like phase containing single strings of cores, depending on the length of attached chains. The disks with mobile monomers assemble into a hexagonal structure, while the particles with longer mobile chains attached to them form a lamellar phase consisting of double strings of cores.
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Affiliation(s)
- Małgorzata Borówko
- Department for the Modelling of Physico-Chemical Processes, Maria Curie-Skłodowska University, 20-031 Lublin, Poland.
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15
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Borówko M, Sokołowski S, Staszewski T, Pizio O. Adsorption of hairy particles with mobile ligands: Molecular dynamics and density functional study. J Chem Phys 2018; 148:044705. [PMID: 29390816 DOI: 10.1063/1.5010687] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We study models of hairy nanoparticles in contact with a hard wall. Each particle is built of a spherical core with a number of ligands attached to it and each ligand is composed of several spherical, tangentially jointed segments. The number of segments is the same for all ligands. Particular models differ by the numbers of ligands and of segments per ligand, but the total number of segments is constant. Moreover, our model assumes that the ligands are tethered to the core in such a manner that they can "slide" over the core surface. Using molecular dynamics simulations we investigate the differences in the structure of a system close to the wall. In order to characterize the distribution of the ligands around the core, we have calculated the end-to-end distances of the ligands and the lengths and orientation of the mass dipoles. Additionally, we also employed a density functional approach to obtain the density profiles. We have found that if the number of ligands is not too high, the proposed version of the theory is capable to predict the structure of the system with a reasonable accuracy.
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Affiliation(s)
- M Borówko
- Department for the Modelling of Physico-Chemical Processes, Maria Curie-Sklodowska University, Gliniana 33, Lublin, Poland
| | - S Sokołowski
- Department for the Modelling of Physico-Chemical Processes, Maria Curie-Sklodowska University, Gliniana 33, Lublin, Poland
| | - T Staszewski
- Department for the Modelling of Physico-Chemical Processes, Maria Curie-Sklodowska University, Gliniana 33, Lublin, Poland
| | - O Pizio
- Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior, 04510 Ciudad de México, Mexico
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16
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Zhao D, Qiu Y, Cheng W, Bi S, Wang H, Wang Q, Liao Y, Peng H, Xie X. Precisely Tuning Helical Twisting Power via Photoisomerization Kinetics of Dopants in Chiral Nematic Liquid Crystals. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:700-708. [PMID: 29268613 DOI: 10.1021/acs.langmuir.7b03786] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
It has been paid much attention to improve the helical twisting power (β) of dopants in chiral nematic liquid crystals (CLCs); however, the correlations between the β value and the molecular structures as well as the interaction with nematic LCs are far from clear. In this work, a series of reversibly photo-switchable axially chiral dopants with different lengths of alkyl or alkoxyl substituent groups have been successfully synthesized through nucleophilic substitution and the thiol-ene click reaction. Then, the effect of miscibility between these dopants and nematic LCs on the β values, as well as the time-dependent decay/growth of the β values upon irradiations, has been investigated. The theoretical Teas solubility parameter shows that the miscibility between dopants and nematic LCs decreases with increasing of the length of substituent groups from dopant 1 to dopant 4. The β value of chiral dopants in nematic LCs decreases from dopant 1 to dopant 4 both at the visible light photostationary state (PSS) and at the UV PSS after UV irradiation. With increasing of the length of substituent groups, the photoisomerization rate constant of dopants increases for trans-cis transformation upon UV irradiation and decreases for the reverse process upon visible light irradiation either in isotropic ethyl acetate or in anisotropic LCs, although the constant in ethyl acetate is several times larger than the corresponding value in LCs. Also, the color of the CLCs could be tuned upon light irradiations. These results enable the precise tuning of the pitch and selective reflection wavelength/color of CLCs, which paves the way to the applications in electro-optic devices, information storage, high-tech anticounterfeit, and so forth.
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Affiliation(s)
| | | | | | - Shuguang Bi
- Hubei Biomass Fibers and Eco-dyeing & Finishing Key Laboratory, College of Chemistry and Chemical Engineering, State Key Laboratory of New Textile Materials and Advanced Processing Technologies, Wuhan Textile University , Wuhan 430073, China
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17
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Fu J, Zhang X, Miao B, Yan D. Light-responsive expansion-contraction of spherical nanoparticle grafted with azopolymers. J Chem Phys 2017; 146:164901. [PMID: 28456201 DOI: 10.1063/1.4981914] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Affiliation(s)
- Jie Fu
- Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Xinghua Zhang
- School of Science, Beijing Jiaotong University, Beijing 100044, China
| | - Bing Miao
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dadong Yan
- Department of Physics, Beijing Normal University, Beijing 100875, China
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18
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Toshchevikov V, Petrova T, Saphiannikova M. Kinetics of light-induced ordering and deformation in LC azobenzene-containing materials. SOFT MATTER 2017; 13:2823-2835. [PMID: 28346548 DOI: 10.1039/c7sm00115k] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Azobenzene-containing smart materials are able to transform the energy of light into directional mechanical stress. We develop a theory of time-dependent light-induced ordering and deformation in azobenzene materials starting from the kinetic equations of photoisomerization. The liquid crystalline (LC) interactions between rod-like trans-isomers are taken into account. Angular selectivity of the photoisomerization known as an "angular hole burning" or the Weigert effect leads to the light-induced ordering and deformation of the azobenzene materials. The time evolution of ordering and deformation is found as a function of intensity of light depending on the opto-mechanical characteristics of the materials, such as probabilities of the optical excitation of trans- and cis-isomers, angular jump during the single isomerization event, viscosity of the materials, strength of the LC interactions in both the isotropic and LC materials, and the angular distribution of chromophores in polymer chains. Established structural-property relationships are in agreement with a number of experiments and can be used for the construction of light-controllable smart materials for practical applications.
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