Modeling and Simulations of Smart and Responsive Polymers

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Processing and Engineering".

Deadline for manuscript submissions: closed (20 May 2024) | Viewed by 9865

Special Issue Editors


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Guest Editor
Lawrence Livermore National Laboratory, Livermore, CA, USA
Interests: multiscale modeling with a focus on structural, mechanical, degradation, and rheological properties; rubber, melt, foam, nanocomposites, smart/responsive polymers, and polymer ink (for 3D printing)
Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
Interests: multiscale modeling; computational materials design; mechanics and physics of soft matter; materials by design; machine learning
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Guest Editor
Lawrence Livermore National Laboratory, Livermore, CA, USA
Interests: high-temperature polymeric materials; applied polymer science; polymer aging; polymer modeling

Special Issue Information

Dear Colleagues,

Smart or responsive polymers are soft materials that display controllable property changes in response to an applied physical, chemical, or biological stimulus. Such changes in properties, usually detectable at the macroscale, are of great interest in diverse technologies such as sensors, actuators, displays, artificial muscles, drug delivery, packaging, bioseparation, self-healing/structural recovery, 3D printing, optical data storage, etc. In most cases of practical interest, the functionality of such materials can be modulated with the inclusion of responsive chemical groups and solvents, co-polymerization, conjugation with nanoparticles, proteins, and various other methods. Given the vast phase space of possible structures (involving both reversibly associative or cross-linked networks), external stimuli (including heat, light, voltage, current, pH, and enzymes), and responses (such as changes in shape, solubility, volume/swelling, crystallization, hydrophobicity, network topology, and optical behavior), only a limited exploration is possible with experiments alone. For the discovery, design, and optimization of smart polymers for future applications, it is essential to gain a fundamental understanding of their dynamic structure/stimulus/property relationships through theory, modeling, and simulations, which should complement and guide further experimental efforts.

This Special Issue welcomes contributions drawing on the cutting-edge theory and computational modeling of stimulus responses in smart polymers. Given the importance of responsive behavior at varied length- and time-scales, we welcome research involving (but not limited to): (1) phenomenological and constitutive models, (2) all-atom molecular dynamics (MD), (3) coarse-grained MD, (4) quantum chemical modeling (optical response and bond-exchange chemistry), (5) continuum-level simulations, and (6) structure–property correlation models.

Dr. Amitesh Maiti
Dr. Ying Li
Dr. Andrew P. Saab
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • smart polymers
  • responsive polymers
  • computer simulation
  • molecular dynamics
  • multiscale modeling
  • self-healing polymers
  • ionomers
  • vitrimers
  • structure-property correlation

Published Papers (6 papers)

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Research

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18 pages, 8533 KiB  
Article
Liquid Crystal Orientation and Shape Optimization for the Active Response of Liquid Crystal Elastomers
by Jorge Luis Barrera, Caitlyn Cook, Elaine Lee, Kenneth Swartz and Daniel Tortorelli
Polymers 2024, 16(10), 1425; https://doi.org/10.3390/polym16101425 - 17 May 2024
Viewed by 252
Abstract
Liquid crystal elastomers (LCEs) are responsive materials that can undergo large reversible deformations upon exposure to external stimuli, such as electrical and thermal fields. Controlling the alignment of their liquid crystals mesogens to achieve desired shape changes unlocks a new design paradigm that [...] Read more.
Liquid crystal elastomers (LCEs) are responsive materials that can undergo large reversible deformations upon exposure to external stimuli, such as electrical and thermal fields. Controlling the alignment of their liquid crystals mesogens to achieve desired shape changes unlocks a new design paradigm that is unavailable when using traditional materials. While experimental measurements can provide valuable insights into their behavior, computational analysis is essential to exploit their full potential. Accurate simulation is not, however, the end goal; rather, it is the means to achieve their optimal design. Such design optimization problems are best solved with algorithms that require gradients, i.e., sensitivities, of the cost and constraint functions with respect to the design parameters, to efficiently traverse the design space. In this work, a nonlinear LCE model and adjoint sensitivity analysis are implemented in a scalable and flexible finite element-based open source framework and integrated into a gradient-based design optimization tool. To display the versatility of the computational framework, LCE design problems that optimize both the material, i.e., liquid crystal orientation, and structural shape to reach a target actuated shapes or maximize energy absorption are solved. Multiple parameterizations, customized to address fabrication limitations, are investigated in both 2D and 3D. The case studies are followed by a discussion on the simulation and design optimization hurdles, as well as potential avenues for improving the robustness of similar computational frameworks for applications of interest. Full article
(This article belongs to the Special Issue Modeling and Simulations of Smart and Responsive Polymers)
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14 pages, 5169 KiB  
Article
Bead–Spring Simulation of Ionomer Melts—Studying the Effects of Chain-Length and Associating Group Fraction on Equilibrium Structure and Extensional Flow Behavior
by Supun S. Mohottalalage, Andrew P. Saab and Amitesh Maiti
Polymers 2023, 15(23), 4560; https://doi.org/10.3390/polym15234560 - 28 Nov 2023
Viewed by 871
Abstract
Ionomers are associative polymers with diverse applications ranging from selective membranes and high-performance adhesives to abrasion- and chemical-resistant coatings, insulation layers, vacuum packaging, and foamed sheets. Within equilibrium melt, the ionic or associating groups are known to form thermally reversible, associative clusters whose [...] Read more.
Ionomers are associative polymers with diverse applications ranging from selective membranes and high-performance adhesives to abrasion- and chemical-resistant coatings, insulation layers, vacuum packaging, and foamed sheets. Within equilibrium melt, the ionic or associating groups are known to form thermally reversible, associative clusters whose presence can significantly affect the system’s mechanical, viscoelastic, and transport properties. It is, thus, of great interest to understand how to control such clusters’ size distribution, shape, and stability through the designed choice of polymer architecture and the ionic groups’ fraction, arrangement, and interaction strength. In this work, we represent linear associating polymers using a Kremer–Grest type bead–spring model and perform large-scale MD simulations to explore the effect of polymer chain-length (l) and fraction (fs) of randomly placed associating groups on the size distribution and stability of formed clusters. We consider different chain-lengths (below and above entanglement), varying fractions of associating groups (represented by ‘sticky’ beads) between 5 and 20%, and a fixed sticky–sticky nonbond interaction strength of four times that between regular non-associating beads. For all melts containing associating groups the equilibrium structure factor S(q) displays a signature ionomer peak at low wave vector q whose intensity increases with increasing fs and l. The average cluster size Nc increases with fs. However, the effect of chain-length on Nc appears to be pronounced only at higher values of fs. Under extensional flows, the computed stress (and viscosity) is higher at higher fs and l regardless of strain rate. Beyond a critical strain rate, we observe fragmentation of the associative clusters, which has interesting effects on the stress/viscous response. Full article
(This article belongs to the Special Issue Modeling and Simulations of Smart and Responsive Polymers)
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14 pages, 5245 KiB  
Article
Multiphysics Modeling Framework for Soft PVC Gel Sensors with Experimental Comparisons
by Justin Neubauer and Kwang J. Kim
Polymers 2023, 15(4), 864; https://doi.org/10.3390/polym15040864 - 9 Feb 2023
Cited by 1 | Viewed by 1377
Abstract
Polyvinyl chloride (PVC) gels have recently been found to exhibit mechanoelectrical transduction or sensing capabilities under compressive loading applications. This phenomenon is not wholly understood but has been characterized as an adsorption-like phenomena under varying amounts and types of plasticizers. A different polymer [...] Read more.
Polyvinyl chloride (PVC) gels have recently been found to exhibit mechanoelectrical transduction or sensing capabilities under compressive loading applications. This phenomenon is not wholly understood but has been characterized as an adsorption-like phenomena under varying amounts and types of plasticizers. A different polymer lattice structure has also been tested, thermoplastic polyurethane, which showed similar sensing characteristics. This study examines mechanical and electrical properties of these gel sensors and proposes a mathematical framework of the underlying mechanisms of mechanoelectrical transduction. COMSOL Multiphysics is used to show solid mechanics characteristics, electrostatic properties, and transport of interstitial plasticizer under compressive loading applications. The solid mechanics takes a continuum mechanics approach and includes a highly compressive Storakers material model for compressive loading applications. The electrostatics and transport properties include charge conservation and a Langmuir adsorption migration model with variable diffusion properties based on plasticizer properties. Results show both plasticizer concentration gradient as well as expected voltage response under varying amounts and types of plasticizers. Experimental work is also completed to show agreeance with the modeling results. Full article
(This article belongs to the Special Issue Modeling and Simulations of Smart and Responsive Polymers)
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12 pages, 4464 KiB  
Article
An Empirical Torsional Spring Model for the Inclined Crack in a 3D-Printed Acrylonitrile Butadiene Styrene (ABS) Cantilever Beam
by Zhichao Yang, Feiyang He and Muhammad Khan
Polymers 2023, 15(3), 496; https://doi.org/10.3390/polym15030496 - 18 Jan 2023
Cited by 1 | Viewed by 1509
Abstract
This paper presents an empirical torsional spring model for the inclined crack on a 3D-printed ABS cantilever beam. The work outlined deals mainly with our previous research about an improved torsional spring model (Khan-He model), which can represent the deep vertical (90°) crack [...] Read more.
This paper presents an empirical torsional spring model for the inclined crack on a 3D-printed ABS cantilever beam. The work outlined deals mainly with our previous research about an improved torsional spring model (Khan-He model), which can represent the deep vertical (90°) crack in the structure. This study used an experimental approach to investigate the relationships between the crack angle and torsional spring stiffness. ABS cantilever beams with different crack depths (1, 1.3 and 1.6 mm) and angles (30, 45, 60, 75 and 90°) were manufactured by fused deposition modelling (FDM). The impact tests were performed to obtain the dynamic response of cracked beams. The equivalent spring stiffness was calculated based on the specimen’s fundamental frequency. The results suggested that an increased crack incline angle yielded higher fundamental frequency and vibration amplitude, representing higher spring stiffness. The authors then developed an empirical spring stiffness model for inclined cracks based on the test data. These results extended the Khan-He model’s application from vertical to inclined crack prediction in FDM ABS structures. Full article
(This article belongs to the Special Issue Modeling and Simulations of Smart and Responsive Polymers)
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14 pages, 2985 KiB  
Article
A New Strategy for Achieving Shape Memory Effects in 4D Printed Two-Layer Composite Structures
by Davood Rahmatabadi, Mohammad Aberoumand, Kianoosh Soltanmohammadi, Elyas Soleyman, Ismaeil Ghasemi, Majid Baniassadi, Karen Abrinia, Ali Zolfagharian, Mahdi Bodaghi and Mostafa Baghani
Polymers 2022, 14(24), 5446; https://doi.org/10.3390/polym14245446 - 13 Dec 2022
Cited by 44 | Viewed by 2846
Abstract
In this study, a new strategy and design for achieving a shape memory effect (SME) and 4D printed two-layer composite structures is unveiled, thanks to fused deposition modeling (FDM) biomaterial printing of commercial filaments, which do not have an SME. We used ABS [...] Read more.
In this study, a new strategy and design for achieving a shape memory effect (SME) and 4D printed two-layer composite structures is unveiled, thanks to fused deposition modeling (FDM) biomaterial printing of commercial filaments, which do not have an SME. We used ABS and PCL as two well-known thermoplastics, and TPU as elastomer filaments that were printed in a two-layer structure. The thermoplastic layer plays the role of constraint for the elastomeric layer. A rubber-to-glass transition of the thermoplastic layer acts as a switching phenomenon that provides the capability of stabilizing the temporary shape, as well as storing the deformation stress for the subsequent recovery of the permanent shape by phase changing the thermoplastic layer in the opposite direction. The results show that ABS–TPU had fixity and recovery ratios above 90%. The PCL–TPU composite structure also demonstrated complete recovery, but its fixity was 77.42%. The difference in the SME of the two composite structures is related to the transition for each thermoplastic and programming temperature. Additionally, in the early cycles, the shape-memory performance decreased, and in the fourth and fifth cycles, it almost stabilized. The scanning electron microscopy (SEM) photographs illustrated superior interfacial bonding and part integrity in the case of multi-material 3D printing. Full article
(This article belongs to the Special Issue Modeling and Simulations of Smart and Responsive Polymers)
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Review

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29 pages, 7694 KiB  
Review
Smart Polymers for Soft Materials: From Solution Processing to Organic Solids
by Debashish Mukherji and Kurt Kremer
Polymers 2023, 15(15), 3229; https://doi.org/10.3390/polym15153229 - 29 Jul 2023
Cited by 4 | Viewed by 1750
Abstract
Polymeric materials are ubiquitous in our everyday life, where they find a broad range of uses—spanning across common household items to advanced materials for modern technologies. In the context of the latter, so called “smart polymers” have received a lot of attention. These [...] Read more.
Polymeric materials are ubiquitous in our everyday life, where they find a broad range of uses—spanning across common household items to advanced materials for modern technologies. In the context of the latter, so called “smart polymers” have received a lot of attention. These systems are soluble in water below their lower critical solution temperature T and often exhibit counterintuitive solvation behavior in mixed solvents. A polymer is known as smart-responsive when a slight change in external stimuli can significantly change its structure, functionm and stability. The interplay of different interactions, especially hydrogen bonds, can also be used for the design of lightweight high-performance organic solids with tunable properties. Here, a general scheme for establishing a structure–property relationship is a challenge using the conventional simulation techniques and also in standard experiments. From the theoretical side, a broad range of all-atom, multiscale, generic, and analytical techniques have been developed linking monomer level interaction details with macroscopic material properties. In this review, we briefly summarize the recent developments in the field of smart polymers, together with complementary experiments. For this purpose, we will specifically discuss the following: (1) the solution processing of responsive polymers and (2) their use in organic solids, with a goal to provide a microscopic understanding that may be used as a guiding tool for future experiments and/or simulations regarding designing advanced functional materials. Full article
(This article belongs to the Special Issue Modeling and Simulations of Smart and Responsive Polymers)
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