Advanced Stimuli-Responsive Polymer Composites

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Smart and Functional Polymers".

Deadline for manuscript submissions: 25 May 2024 | Viewed by 9966

Special Issue Editor

German Aerospace Center (DLR), DLR-Institute of Material Physics in Space, Köln, Germany
Interests: polymer physics; responsive polymers; thin films; neutron scattering; X-ray scattering

Special Issue Information

Dear Colleagues,

Stimuli-responsive polymer composites feature highly diverse functional properties in response to various environmental stimuli such as temperature, light, pH, magnetic and electric fields, and enzymes. In recent decades, the response mechanisms of numerous selected polymer matrices and functional additives (e.g., metals, ceramics, or nanostructured carbon) have been the subject of intensive studies, and a fundamental understanding of the structure–dynamics–performance relationship has been developed. Consequently, this enabled the application of stimuli-responsive polymeric materials in various emerging fields such as biomedical devices, electronics, and soft robotics. With recent advancements in nano and polymer chemistry, these materials increased in complexity, and their versatility increased as well (e.g., multiple components with individual responses towards several stimuli)

This Special Issue focuses on the latest achievements in the material and structure design, characterization, and employment of novel and advanced stimuli-responsive polymer composites. Review and regular research articles as well as short communication of all cross-disciplinary research studies, in which novel stimuli-responsive polymer composites are involved, are encouraged to publish their recent findings in this Special Issue of Polymers.

Dr. Lucas Kreuzer
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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Keywords

  • stimuli-responsive materials
  • polymer composites
  • advanced materials
  • nanoparticles
  • biomedical
  • soft robotics
  • electronics

Published Papers (7 papers)

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Research

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9 pages, 1583 KiB  
Communication
Transparent and Flexible Actuator Based on a Hybrid Dielectric Layer of Wavy Polymer and Dielectric Fluid Mixture
Polymers 2024, 16(2), 188; https://doi.org/10.3390/polym16020188 - 08 Jan 2024
Viewed by 499
Abstract
Transparent and flexible vibrotactile actuators play an essential role in human–machine interaction applications by providing mechanical stimulations that can effectively convey haptic sensations. In the present study, we fabricated an electroactive, flexible, and transparent vibrotactile actuator with a dielectric layer including a dielectric [...] Read more.
Transparent and flexible vibrotactile actuators play an essential role in human–machine interaction applications by providing mechanical stimulations that can effectively convey haptic sensations. In the present study, we fabricated an electroactive, flexible, and transparent vibrotactile actuator with a dielectric layer including a dielectric elastomer and dielectric fluid mixture. The dielectric fluid mixture of propylene carbonate (PC) and acetyl tributyl citrate (ATBC) was injected to obtain a transparent dielectric layer. To further improve the haptic performance, different weight ratios of dielectric fluid (PC: ATBC) were injected. The fabricated vibrotactile actuators based on a transparent dielectric layer were investigated for their electrical and electromechanical behavior. The proposed actuators generate a large vibrational intensity (~2.5 g) in the range of 200–250 Hz. Hence, the proposed actuators open up a new class of vibrotactile actuators for possible use in various domains, including robotics, smart textiles, teleoperation, and the metaverse. Full article
(This article belongs to the Special Issue Advanced Stimuli-Responsive Polymer Composites)
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7 pages, 1793 KiB  
Communication
Angle-Independent Color Change in Thermoresponsive Gel-Immobilized Colloidal Amorphous Film Attached to PET Substrate
Polymers 2023, 15(24), 4661; https://doi.org/10.3390/polym15244661 - 10 Dec 2023
Viewed by 683
Abstract
Gel-immobilized colloidal amorphous structures comprise short-range-ordered monodisperse submicrometer particles embedded into a soft polymer gel. They exhibit an angle-independent structural color that is tunable in response to external stimuli via a volume change in the gel, which has significant potential for the development [...] Read more.
Gel-immobilized colloidal amorphous structures comprise short-range-ordered monodisperse submicrometer particles embedded into a soft polymer gel. They exhibit an angle-independent structural color that is tunable in response to external stimuli via a volume change in the gel, which has significant potential for the development of sensors that respond to stimuli via angle-independent color changes. In this study, the amorphous structure of a charged colloidal suspension in water was immobilized in a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) gel film and simultaneously attached to a polyethylene terephthalate (PET) substrate. The gel film exhibited a uniform angle-independent color that changed in response to changes in temperature (i.e., thermosensitivity). Attachment to the PET substrate suppressed changes in the gel film area and film distortion, despite significant volume changes in the gel. Consequently, the degree of thermosensitivity was enhanced. The PET-attached gel-immobilized colloidal amorphous film was easy to handle and had excellent flexibility, allowing it to wrap around the surfaces of curved objects. These features are advantageous for sensor applications. Full article
(This article belongs to the Special Issue Advanced Stimuli-Responsive Polymer Composites)
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16 pages, 6528 KiB  
Article
Three-Dimensional Printing of Shape Memory Liquid Crystalline Thermoplastic Elastomeric Composites Using Fused Filament Fabrication
Polymers 2023, 15(19), 3961; https://doi.org/10.3390/polym15193961 - 30 Sep 2023
Viewed by 787
Abstract
Liquid crystalline elastomers (LCEs) are stimuli-responsive materials utilised in shape memory applications. The processability of these materials via advanced manufacturing is being paid increasing attention to advance their volume production on an industrial scale. Fused filament fabrication (FFF) is an extrusion-based additive manufacturing [...] Read more.
Liquid crystalline elastomers (LCEs) are stimuli-responsive materials utilised in shape memory applications. The processability of these materials via advanced manufacturing is being paid increasing attention to advance their volume production on an industrial scale. Fused filament fabrication (FFF) is an extrusion-based additive manufacturing (AM) technique that offers the potential to address this. The critical challenge, however, is the rheological characteristics of LCEs that need to be tuned to achieve a facile processability through the extrusion-based method. In this work, new filaments of liquid crystalline thermoplastic elastomer (LCTPE) and its composites with lignin were made by the ternary system of LCE, thermoplastic polyurethane (TPU), and lignin. The results showed that TPU improves the melt flow index of the LCTPE system to approximately 10.01 g/10 min, while adding lignin further enhances the value of this index for the composites up to 21.82 g/10 min. The microstructural analysis indicated that the effective distribution of lignin and reduced domain size of the LCEs in the ternary blend contribute to the enhanced flowability of this filament through 3D printing. Samples of 3D-printed LCTPE and LCTPE/lignin composites maintained their shape memory characteristics via thermomechanical activation. Full shape recovery of the new LCTPE matrix and its composites with lignin was achieved in 39 s and 32 s at 130 °C, followed by 28 s and 24 s at 160 °C, respectively. The successful fabrication of LCTPE and LCTPE/lignin composite samples through 3D printing demonstrates a potential procedure for processing these shape memory materials using the FFF technique, and lignin offers a sustainable and cost-effective material solution that enhances the properties of this composite material. Full article
(This article belongs to the Special Issue Advanced Stimuli-Responsive Polymer Composites)
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19 pages, 8587 KiB  
Article
Synthesis and Comparative Study of Polyether-b-polybutadiene-b-polyether Triblock Copolymers for Use as Polyurethanes
Polymers 2023, 15(16), 3486; https://doi.org/10.3390/polym15163486 - 21 Aug 2023
Viewed by 743
Abstract
In this paper, the effects of HTPBs with different main-chain microstructures on their triblock copolymers and polyurethane properties were investigated. Three polyether-modified HTPB triblock copolymers were successfully synthesized via a cationic ring-opening copolymerization reaction using three HTPBs with different microstructures prepared via three [...] Read more.
In this paper, the effects of HTPBs with different main-chain microstructures on their triblock copolymers and polyurethane properties were investigated. Three polyether-modified HTPB triblock copolymers were successfully synthesized via a cationic ring-opening copolymerization reaction using three HTPBs with different microstructures prepared via three different polymerization methods as the macromolecular chain transfer agents and tetrahydrofuran (THF) and propylene oxide (PO) as the copolymerization monomers. Finally, the corresponding polyurethane elastomers were prepared using the three triblock copolymers as soft segments and toluene diisocyanate (TDI) as hard segments. The results of an analysis of the triblock copolymers showed that the triblock copolymers had lower viscosity and glass transition temperature (Tg) values as the HTPB 1,2 structure content decreased, although the effect on the thermal decomposition temperature was not significant. An analysis of the polyurethane elastomers revealed that as the content of the 1,2 structure in HTPB increased, its corresponding polyurethane elastomers showed a gradual increase in breaking strength and a gradual decrease in elongation at break. In addition, PU-1 had stronger crystallization properties compared to PU-2 and PU-3. However, the differences in the microstructures of the HTPBs did not seem to have much effect on the surface properties of the polyurethane elastomers. Full article
(This article belongs to the Special Issue Advanced Stimuli-Responsive Polymer Composites)
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16 pages, 2435 KiB  
Article
Role of Bovine Serum Albumin Addition in Micellization and Gel Formation of Poloxamer 407
Polymers 2023, 15(11), 2465; https://doi.org/10.3390/polym15112465 - 26 May 2023
Cited by 1 | Viewed by 1089
Abstract
The combination of the thermoresponsive polymer and protein has demonstrated great promise in its applications in drug delivery and tissue engineering fields. This study described the impact of bovine serum albumin (BSA) on the micellization and sol–gel transition behaviors of poloxamer 407 (PX). [...] Read more.
The combination of the thermoresponsive polymer and protein has demonstrated great promise in its applications in drug delivery and tissue engineering fields. This study described the impact of bovine serum albumin (BSA) on the micellization and sol–gel transition behaviors of poloxamer 407 (PX). The micellization of aqueous PX solutions with and without BSA was examined using isothermal titration calorimetry. In the calorimetric titration curves, the pre-micellar region, the transition concentration region, and the post-micellar region were observed. The presence of BSA had no noticeable impact on critical micellization concentration, but the inclusion of BSA caused the pre-micellar region to expand. In addition to studying the self-organization of PX at a particular temperature, the temperature-induced micellization and gelation of PX were also explored using differential scanning calorimetry and rheology. The incorporation of BSA had no discernible effect on critical micellization temperature (CMT), but it did affect gelation temperature (Tgel) and gel integrity of PX-based systems. The response surface approach illustrated the linear relation between the compositions and the CMT. The major factor affecting the CMT of the mixtures was the concentration of PX. The alteration of the Tgel and the gel integrity were discovered to be a consequence of the intricate interaction between PX and BSA. BSA mitigated the inter-micellar entanglements. Hence, the addition of BSA demonstrated a modulating influence on Tgel and a softening effect on gel integrity. Understanding the influence of serum albumin on the self-assembly and gelation of PX will enable the creation of thermoresponsive drug delivery and tissue engineering systems with controlled gelation temperatures and gel strength. Full article
(This article belongs to the Special Issue Advanced Stimuli-Responsive Polymer Composites)
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20 pages, 6918 KiB  
Article
Stimuli-Responsive and Antibacterial Cellulose-Chitosan Hydrogels Containing Polydiacetylene Nanosheets
Polymers 2023, 15(5), 1062; https://doi.org/10.3390/polym15051062 - 21 Feb 2023
Cited by 9 | Viewed by 1955
Abstract
Herein, we report a stimuli-responsive hydrogel with inhibitory activity against Escherichia coli prepared by chemical crosslinking of carboxymethyl chitosan (CMCs) and hydroxyethyl cellulose (HEC). The hydrogels were prepared by esterification of chitosan (Cs) with monochloroacetic acid to produce CMCs which were then chemically [...] Read more.
Herein, we report a stimuli-responsive hydrogel with inhibitory activity against Escherichia coli prepared by chemical crosslinking of carboxymethyl chitosan (CMCs) and hydroxyethyl cellulose (HEC). The hydrogels were prepared by esterification of chitosan (Cs) with monochloroacetic acid to produce CMCs which were then chemically crosslinked to HEC using citric acid as the crosslinking agent. To impart a stimuli responsiveness property to the hydrogels, polydiacetylene-zinc oxide (PDA-ZnO) nanosheets were synthesized in situ during the crosslinking reaction followed by photopolymerization of the resultant composite. To achieve this, ZnO was anchored on carboxylic groups in 10,12-pentacosadiynoic acid (PCDA) layers to restrict the movement of the alkyl portion of PCDA during crosslinking CMCs and HEC hydrogels. This was followed by irradiating the composite with UV radiation to photopolymerize the PCDA to PDA within the hydrogel matrix so as to impart thermal and pH responsiveness to the hydrogel. From the results obtained, the prepared hydrogel had a pH-dependent swelling capacity as it absorbed more water in acidic media as compared to basic media. The incorporation of PDA-ZnO resulted in a thermochromic composite responsive to pH evidenced by a visible colour transition from pale purple to pale pink. Upon swelling, PDA-ZnO-CMCs-HEC hydrogels had significant inhibitory activity against E. coli attributed to the slow release of the ZnO nanoparticles as compared to CMCs-HEC hydrogels. In conclusion, the developed hydrogel was found to have stimuli-responsive properties and inhibitory activity against E. coli attributed to zinc nanoparticles. Full article
(This article belongs to the Special Issue Advanced Stimuli-Responsive Polymer Composites)
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Review

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59 pages, 22832 KiB  
Review
Smart Polymer Surfaces with Complex Wrinkled Patterns: Reversible, Non-Planar, Gradient, and Hierarchical Structures
Polymers 2023, 15(3), 612; https://doi.org/10.3390/polym15030612 - 25 Jan 2023
Cited by 5 | Viewed by 3215
Abstract
This review summarizes the relevant developments in preparing wrinkled structures with variable characteristics. These include the formation of smart interfaces with reversible wrinkle formation, the construction of wrinkles in non-planar supports, or, more interestingly, the development of complex hierarchically structured wrinkled patterns. Smart [...] Read more.
This review summarizes the relevant developments in preparing wrinkled structures with variable characteristics. These include the formation of smart interfaces with reversible wrinkle formation, the construction of wrinkles in non-planar supports, or, more interestingly, the development of complex hierarchically structured wrinkled patterns. Smart wrinkled surfaces obtained using light-responsive, pH-responsive, temperature-responsive, and electromagnetic-responsive polymers are thoroughly described. These systems control the formation of wrinkles in particular surface positions and the reversible construction of planar-wrinkled surfaces. This know-how of non-planar substrates has been recently extended to other structures, thus forming wrinkled patterns on solid, hollow spheres, cylinders, and cylindrical tubes. Finally, this bibliographic analysis also presents some illustrative examples of the potential of wrinkle formation to create more complex patterns, including gradient structures and hierarchically multiscale-ordered wrinkles. The orientation and the wrinkle characteristics (amplitude and period) can also be modulated according to the requested application. Full article
(This article belongs to the Special Issue Advanced Stimuli-Responsive Polymer Composites)
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