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Smart Polymeric Micro/Nanomaterials

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Macromolecular Chemistry".

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 23643

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Special Issue Editors

Dr. Naokazu Idota

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Guest Editor

Laboratory for Zero-Carbon Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1-N1-6, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
Interests: micro-/nanofluidics; organic–inorganic hybrid material; stimuli-responsive polymers

Prof. Dr. Takehiko Tsukahara

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Guest Editor

Laboratory for Zero-Carbon Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1-N1-6, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
Interests: nuclear fuel cycle; separation and analysis; rare earth; geological disposal; micro-/nanotechnologies; supercritical fluids; functional material; responsive polymer

Special Issue Information

Dear Colleagues,

Smart polymers are known as stimuli-responsive polymers which change discontinuously and sensitively their physicochemical properties in response to small changes in external stimuli such as temperature, pH, light, mechanical stress, and magnetic field. Such unique features of smart polymers have been found in various forms, including aqueous solutions, bulk films, nanoassemblies, nanofibers, adsorption or surface modification on solid substrates, organic–inorganic nanocomposites, and cross-linking hydrogels. Based on these fundamental technologies and researchers’ flexible ideas, the creation of superior functional materials, e.g., sensors, actuators, optical materials, shape memory materials, self-healing materials, micro-/nanofluidic materials, battery materials, nanocarriers, separation matrices, bioconjugates, and cell culture substrates, has been successfully realized. It is noteworthy that the sensitive property changes of the smart polymeric materials allow dynamic and reversible on–off switching of their size, shape, dispersibility in media, surface wettability, permeability, conductivity, adsorption, and molecular interactions, since they can be controlled just by applying external stimuli in a non-contact manner or spontaneous environmental changes. The dynamic function should provide positive impacts to conventional static systems, and contributes to advances to the fields of chemistry, biology, materials sciences, bioengineering, medicine, drug discovery, energy, and environmental engineering. This Special Issue focuses on the overall of functional micro-/nanomaterials based on smart polymers, including synthesis, characterization and possible applications. Original research papers as well as review articles are welcome.

Dr. Naokazu Idota
Prof. Dr. Takehiko Tsukahara
Guest Editors

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Keywords

smart polymers
responsive polymers
sensors
actuators
optical materials
shape memory materials
self-healing materials
micro/nanofluidic materials
battery materials
nanocarriers
separation matrices
bioconjugates
cell culture substrates

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Published Papers (12 papers)

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Research

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15 pages, 4218 KiB

Open AccessFeature PaperArticle

Synthesis and Characterization of Side-Chain Liquid-Crystalline Block Copolymers Containing Cyano-Terminated Phenyl Benzoate Moieties

by Kaito Takahashi, Daisuke Taguchi, Takashi Kajitani, Takanori Fukushima, Shoichi Kubo and Atsushi Shishido

Molecules 2023, 28(23), 7849; https://doi.org/10.3390/molecules28237849 - 29 Nov 2023

Cited by 1 | Viewed by 1314

Abstract

Block copolymers, known for their capacity to undergo microphase separation, spontaneously yield various periodic nanostructures. These precisely controlled nanostructures have attracted considerable interest due to their potential applications in microfabrication templates, conducting films, filter membranes, and other areas. However, it is crucial to acknowledge that microphase-separated structures typically exhibit random alignment, making alignment control a pivotal factor in functional material development. To address this challenge, researchers have explored the use of block copolymers containing liquid-crystalline (LC) polymers, which offer a promising technique for alignment control. The molecular structure and LC behavior of these polymers significantly impact the morphology and alignment of microphase-separated structures. In this study, we synthesized LC diblock copolymers with cyano-terminated phenyl benzoate moieties and evaluated the microphase-separated structures and molecular alignment behaviors. The LC diblock copolymers with a narrow molecular weight distribution were synthesized by atom transfer radical polymerization. Small angle X-ray scattering measurements revealed that the block copolymers exhibit smectic LC phases and form cylinder structures with a lattice period of about 18 nm by microphase separation. The examination of block copolymer films using polarized optical microscopy and polarized UV-visible absorption spectroscopy corroborated that the LC moieties were uniaxially aligned along the alignment treatment direction. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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13 pages, 3468 KiB

Open AccessArticle

Fabrication of AIE Polymer-Functionalized Reduced Graphene Oxide for Information Storage

by Kai Gao, Wei Li, Xiaoyang Wang, Sai Sun and Bin Zhang

Molecules 2023, 28(17), 6271; https://doi.org/10.3390/molecules28176271 - 27 Aug 2023

Viewed by 1183

Abstract

Reduced graphene oxide (RGO) has been extensively studied and applied in optoelectronic systems, but its unstable dispersion in organic solvents has limited its application. To overcome this problem, the newly designed and developed aggregation-induced emission (AIE) material poly[(9,9-bis(6-azidohexyl)-9H-fluorene)-alt-(9-(4-(1,2,2-triphenylvinyl)phenyl)-9H-carbazole)] (PAFTC) was covalently grafted onto RGO to produce (PFTC-g-RGO). The solubility of two-dimensional graphene was improved by incorporating it into the backbone of PAFTC to form new functional materials. In resistive random access memory (RRAM) devices, PFTC-g-RGO was used as the active layer material after it was characterized. The fabricated Al/PFTC-g-RGO/ITO device exhibited nonvolatile bistable resistive switching performances with a long retention time of over 10⁴ s, excellent endurance of over 200 switching cycles, and an impressively low turn-ON voltage. This study provides important insights into the future development of AIE polymer-functionalized nanomaterials for information storage. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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12 pages, 5570 KiB

Open AccessArticle

Copper and Zinc Metal–Organic Frameworks with Bipyrazole Linkers Display Strong Antibacterial Activity against Both Gram+ and Gram− Bacterial Strains

by Sonila Xhafa, Laura Olivieri, Corrado Di Nicola, Riccardo Pettinari, Claudio Pettinari, Alessia Tombesi and Fabio Marchetti

Molecules 2023, 28(16), 6160; https://doi.org/10.3390/molecules28166160 - 21 Aug 2023

Cited by 8 | Viewed by 1544

Abstract

Here, we report a new synthetic protocol based on microwave-assisted synthesis (MAS) for the preparation of higher yields of zinc and copper in MOFs based on different bis(pyrazolyl)-tagged ligands ([M(BPZ)]_n where M = Zn(II), Cu(II), H₂BPZ = 4,4′-bipyrazole, [M(BPZ-NH₂)]_n where M = Zn(II), Cu(II); H₂BPZ-NH₂ = 3-amino-4,4′-bipyrazole, and [M_x(Me₄BPZPh)] where M = Zn(II), x = 1; Cu(II), x = 2; H₂Me₄BPZPh = bis-4′-(3′,5′-dimethyl)-pyrazolylbenzene) and, for the first time, a detailed study of their antibacterial activity, tested against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria, as representative agents of infections. The results show that all MOFs exert a broad-spectrum activity and strong efficiency in bacterial growth inhibition, with a mechanism of action based on the surface contact of MOF particles with bacterial cells through the so-called “chelation effect” and reactive oxygen species (ROS) generation, without a significant release of Zn(II) and Cu(II) ions. In addition, morphological changes were elucidated by using a scanning electron microscope (SEM) and bacterial cell damage was further confirmed by a confocal laser scanning microscopy (CLSM) test. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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12 pages, 5671 KiB

Open AccessArticle

Cellular Internalization and Exiting Behavior of Zwitterionic 4-Armed Star-Shaped Polymers

by Yuta Yoshizaki and Tomohiro Konno

Molecules 2023, 28(11), 4479; https://doi.org/10.3390/molecules28114479 - 1 Jun 2023

Cited by 7 | Viewed by 1714

Abstract

The zwitterionic phospholipid polymer poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (PMB) is amphiphilic copolymer, and it has been reported to directly penetrate cell membranes and have good cytocompatibility. Conventional PMBs are linear-type random copolymers that are polymerized by a free radical polymerization technique. In contrast, star-shaped polymers, or simple branched-type polymers, have unique properties compared to the linear types, for example, a viscosity based on the effect of the excluded volume. In this study, a branched architecture was introduced into a PMB molecular structure, and a 4-armed star-shaped PMB (4armPMB) was synthesized by an atom transfer radical polymerization (ATRP) technique known as living radical polymerization. Linear-type PMB was also synthesized using ATRP. The effects of the polymer architecture on cytotoxicity and cellular uptake were investigated. Both 4armPMB and LinearPMB were successfully synthesized, and these polymers were verified to be water soluble. Pyrene fluorescence in the polymer solution indicated that the architecture had no effect on the behavior of the polymer aggregates. In addition, these polymers caused no cytotoxicity or cell membrane damage. The 4armPMB and LinearPMB penetrated into the cells after a short incubation period, with similar rates. In contrast, the 4armPMB showed a quicker back-diffusion from the cells than that of LinearPMB. The 4armPMB showed fast cellular internalization and exiting behaviors. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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17 pages, 5229 KiB

Open AccessArticle

Aggregation-Based Bacterial Separation with Gram-Positive Selectivity by Using a Benzoxaborole-Modified Dendrimer

by Ayame Mikagi, Yotaro Takahashi, Nobuyuki Kanzawa, Yota Suzuki, Yuji Tsuchido, Takeshi Hashimoto and Takashi Hayashita

Molecules 2023, 28(4), 1704; https://doi.org/10.3390/molecules28041704 - 10 Feb 2023

Cited by 2 | Viewed by 1961

Abstract

Antimicrobial-resistant (AMR) bacteria have become a critical global issue in recent years. The inefficacy of antimicrobial agents against AMR bacteria has led to increased difficulty in treating many infectious diseases. Analyses of the environmental distribution of bacteria are important for monitoring the AMR problem, and a rapid as well as viable pH- and temperature-independent bacterial separation method is required for collecting and concentrating bacteria from environmental samples. Thus, we aimed to develop a useful and selective bacterial separation method using a chemically synthesized nanoprobe. The metal-free benzoxaborole-based dendrimer probe BenzoB-PAMAM(+), which was synthesized from carboxy-benzoxaborole and a poly(amidoamine) (PAMAM) dendrimer, could help achieve Gram-positive bacterial separation by recognizing Gram-positive bacterial surfaces over a wide pH range, leading to the formation of large aggregations. The recognition site of benzoxaborole has a desirable high acidity and may therefore be responsible for the improved Gram-positive selectivity. The Gram-positive bacterial aggregation was then successfully collected by using a 10 μm membrane filter, with Gram-negative bacteria remaining in the filtrate solution. BenzoB-PAMAM(+) will thus be useful for application in biological analyses and could contribute to further investigations of bacterial distributions in environmental soil or water. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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10 pages, 1170 KiB

Open AccessArticle

Behavior of PNIPAM Microgels in Different Organic Solvents

by Galina A. Komarova, Elena Yu. Kozhunova and Igor I. Potemkin

Molecules 2022, 27(23), 8549; https://doi.org/10.3390/molecules27238549 - 5 Dec 2022

Cited by 5 | Viewed by 2790

Abstract

In this research, we studied, in detail, the behavior of common PNIPAM microgels, obtained through surfactant-free precipitation polymerization, in a number of organic solvents. We showed that many of the selected solvents serve as good solvents for the PNIPAM microgels and that the size and architecture of the microgels depend on the solvent chosen. Expanding the range of solvents used for PNIPAM microgel incubation greatly enhances the possible routes for microparticle functionalization and modification, as well as the encapsulation of water-insoluble species. In this demonstration, we successfully encapsulated water-insoluble Sudan III dye in PNIPAM microgels and prepared the aqueous dispersions of such composite-colored microparticles. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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22 pages, 3929 KiB

Open AccessArticle

Development of Novel Polypropylene Syntactic Foams Containing Paraffin Microcapsules for Thermal Energy Storage Applications

by Francesco Galvagnini, Andrea Dorigato, Luca Fambri and Alessandro Pegoretti

Molecules 2022, 27(23), 8520; https://doi.org/10.3390/molecules27238520 - 3 Dec 2022

Cited by 2 | Viewed by 1639

Abstract

polypropylene (PP) syntactic foams (SFs) containing hollow glass microspheres (HGMs) possess low density and elevated mechanical properties, which can be tuned according to the specific application. A possible way to improve their multifunctionality could be the incorporation of organic Phase Change Materials (PCMs), widely used for thermal energy storage (TES) applications. In the present work, a PCM constituted by encapsulated paraffin, having a melting temperature of 57 °C, was embedded in a compatibilized polypropylene SF by melt compounding and hot pressing at different relative amounts. The rheological, morphological, thermal, and mechanical properties of the prepared materials were systematically investigated. Rheological properties in the molten state were strongly affected by the introduction of both PCMs and HGMs. As expected, the introduction of HGMs reduced both the foam density and thermal conductivity, while the enthalpy of fusion (representing the TES capability) was proportional to the PCM concentration. The mechanical properties of these foams were improved by the incorporation of HGMs, while they were reduced by addition of PCMs. Therefore, the combination of PCMs and HGMs in a PP matrix generated multifunctional materials with tunable thermo-mechanical properties, with a wide range of applications in the automotive, oil, textile, electronics, and aerospace fields. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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18 pages, 3142 KiB

Open AccessArticle

Stimuli-Responsive Polypeptide Nanoparticles for Enhanced DNA Delivery

by Olga Korovkina, Dmitry Polyakov, Viktor Korzhikov-Vlakh and Evgenia Korzhikova-Vlakh

Molecules 2022, 27(23), 8495; https://doi.org/10.3390/molecules27238495 - 2 Dec 2022

Cited by 7 | Viewed by 1785

Abstract

The development of non-viral delivery systems for effective gene therapy is one of the current challenges in modern biomedicinal chemistry. In this paper, the synthesis of pH- and redox-responsive amphiphilic polypeptides for intracellular DNA delivery is reported and discussed. Two series of polypeptides consisting of L-lysine, L-phenylalanine, L-histidine, and L-cysteine as well as the same amino acids with L-glutamic acid were synthesized by a combination of copolymerization of N-carboxyanhydrides of α-amino acids and post-polymerization modification of the resulting copolymers. The presence of histidine provided pH-sensitive properties under weakly acidic conditions specific to endosomal pH. In turn, the presence of cysteine allowed for the formation of redox-responsive disulfide bonds, which stabilized the self-assembled nanoparticles in the extracellular environment but could degrade inside the cell. The formation of intraparticle disulfide bonds resulted in their compactization from 200–250 to 55–100 nm. Empty and pDNA-loaded cross-linked nanoparticles showed enhanced stability in various media compared to non-crosslinked nanoparticles. At the same time, the addition of glutathione promoted particle degradation and nucleic acid release. The delivery systems were able to retain their size and surface charge at polypeptide/pDNA ratios of 10 or higher. GFP expression in HEK 293 was induced by the delivery of pEGFP-N3 with the developed polypeptide nanoparticles. The maximal transfection efficacy (70%) was observed when the polypeptide/pDNA ratio was 100. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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8 pages, 1625 KiB

Open AccessFeature PaperArticle

Programed Thermoresponsive Polymers with Cleavage-Induced Phase Transition

by Yukiya Kitayama, Yasumichi Yazaki, Junya Emoto, Eiji Yuba and Atsushi Harada

Molecules 2022, 27(18), 6082; https://doi.org/10.3390/molecules27186082 - 18 Sep 2022

Cited by 1 | Viewed by 1621

Abstract

A new programed upper critical solution temperature-type thermoresponsive polymer was developed using water-soluble anionic polymer conjugates derived from polyallylamine and phthalic acid with cleavage-induced phase transition property. Intrinsic charge inversion from anion to cation of the polymer side chain is induced through a side chain cleavage reaction in acidic aqueous media. With the progress of side chain cleavage under fixed external conditions, the polymer conjugates express a thermoresponsive property, followed by shifting a phase boundary due to the change in polymer composition. When the phase transition boundary eventually reached the examined temperature, phase transition occurs under fixed external conditions. Such new insight obtained in this study opens up the new concept of time-programed stimuli-responsive polymer possessing a cleavage-induced phase transition. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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Review

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25 pages, 7298 KiB

Open AccessReview

Smart Responsive Microneedles for Controlled Drug Delivery

by Zhenzhen Qi, Zheng Yan, Guohongfang Tan, Subhas C. Kundu and Shenzhou Lu

Molecules 2023, 28(21), 7411; https://doi.org/10.3390/molecules28217411 - 3 Nov 2023

Cited by 3 | Viewed by 3131

Abstract

As an emerging technology, microneedles offer advantages such as painless administration, good biocompatibility, and ease of self-administration, so as to effectively treat various diseases, such as diabetes, wound repair, tumor treatment and so on. How to regulate the release behavior of loaded drugs in polymer microneedles is the core element of transdermal drug delivery. As an emerging on-demand drug-delivery technology, intelligent responsive microneedles can achieve local accurate release of drugs according to external stimuli or internal physiological environment changes. This review focuses on the research efforts in smart responsive polymer microneedles at home and abroad in recent years. It summarizes the response mechanisms based on various stimuli and their respective application scenarios. Utilizing innovative, responsive microneedle systems offers a convenient and precise targeted drug delivery method, holding significant research implications in transdermal drug administration. Safety and efficacy will remain the key areas of continuous efforts for research scholars in the future. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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37 pages, 8426 KiB

Open AccessReview

A Review of Research Progress on the Performance of Intelligent Polymer Gel

by Shuangchun Yang, Zhenye Liu, Yi Pan, Jian Guan, Peng Yang and Muratbekova Asel

Molecules 2023, 28(10), 4246; https://doi.org/10.3390/molecules28104246 - 22 May 2023

Cited by 5 | Viewed by 2176

Abstract

Intelligent polymer gel, as a popular polymer material, has been attracting much attention for its application. An intelligent polymer gel will make corresponding changes to adapt to the environment after receiving stimuli; therefore, an intelligent polymer gel can play its role in many fields. With the research on intelligent polymer gels, there is great potential for applications in the fields of drug engineering, molecular devices, and biomedicine in particular. The strength and responsiveness of the gels can be improved under different configurations in different technologies to meet the needs in these fields. There is no discussion on the application of intelligent polymer gels in these fields; therefore, this paper reviews the research progress of intelligent polymer gel, describes the important research of some intelligent polymer gel, summarizes the research progress and current situation of intelligent polymer gel in the environment of external stimulation, and discusses the performance and future development direction of intelligent polymer gel. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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12 pages, 1363 KiB

Open AccessReview

Recent Advances in Imaging Agents Anchored with pH (Low) Insertion Peptides for Cancer Theranostics

by Yu-Cheng Liu, Zhi-Xian Wang, Jing-Yi Pan, Ling-Qi Wang, Xin-Yi Dai, Ke-Fei Wu, Xue-Wei Ye and Xiao-Ling Xu

Molecules 2023, 28(5), 2175; https://doi.org/10.3390/molecules28052175 - 26 Feb 2023

Cited by 9 | Viewed by 1997

Abstract

The acidic extracellular microenvironment has become an effective target for diagnosing and treating tumors. A pH (low) insertion peptide (pHLIP) is a kind of peptide that can spontaneously fold into a transmembrane helix in an acidic microenvironment, and then insert into and cross the cell membrane for material transfer. The characteristics of the acidic tumor microenvironment provide a new method for pH-targeted molecular imaging and tumor-targeted therapy. As research has increased, the role of pHLIP as an imaging agent carrier in the field of tumor theranostics has become increasingly prominent. In this paper, we describe the current applications of pHLIP-anchored imaging agents for tumor diagnosis and treatment in terms of different molecular imaging methods, including magnetic resonance T1 imaging, magnetic resonance T2 imaging, SPECT/PET, fluorescence imaging, and photoacoustic imaging. Additionally, we discuss relevant challenges and future development prospects. Full article

(This article belongs to the Special Issue Smart Polymeric Micro/Nanomaterials)

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