Temperature-responsive Materials Research Articles

Tetra Dansylamides substituted cyclen and cyclam Macrocycles as fluorescent sensing probes for metal ions and Temperature-Responsive Materials in dopped Polymers

Two novel tetra-dansyl derivatives incorporating cyclen (1,4,7,10-tetraazacyclododecane) and cyclam (1,4,8,11-tetraazacyclotetradecane) macrocycles have been synthesized, thoroughly characterized, and their photophysical properties examined, both in solution and in the solid state. These compounds exhibit fluorescence emission with quantum yields up to 40%, varying significantly with different solvents. They also display positive solvatofluorochromic behavior, with emissions ranging from green to yellow colours. Kamlet-Taft studies were conducted to better understand solute-solvent interactions. Furthermore, aggregation-induced emission was observed in solutions with high water content, confirmed via dynamic light scattering. Given the intrinsic properties of these compounds, their potential for environmental remediation was explored through metal ion sensing studies. Compounds L1 and L2 demonstrated high sensitivity to Cu2+ and Hg2+ ions, significantly modulating their emission, with L2 capable of detecting and quantifying Hg2+ concentrations as low as 2 to 3 μM. Additionally, the solid-state emission of these compounds encouraged an investigation into their potential as temperature sensors. Several doped polymer thin films were fabricated, establishing a linear relationship with temperature beyond their melting point. These findings suggest that these tetra-chromophoric compounds hold promise as molecular thermometers.

Gelatin-based ionic hydrogel for intelligent fire-alarm system with considerable toughness, flame retardancy, and thermoelectric performance

Temperature-responsive materials with excellent reliability, sensitivity, and flame-retardant properties have always been an urgent need in the field of intelligent fire protection. In this discourse, we introduce a novel thermosensitive ionic hydrogel coating (gelatin/poly(acrylamide-co-acrylic acid)/CaCl2/spindle-shaped aluminum hydroxide nanosheet/glycerol, HCA) synthesized via free radical polymerization. HCA not only demonstrates considerable mechanical properties with a fracture strain of up to 842.5 % and a maximum tensile strength of 0.77 MPa but also exhibits notable flame retardancy and adhesion. It effectively covers combustible surfaces, providing outstanding fire protection. Notably, HCA boasts a Seebeck coefficient of up to 10.1 mV/K, significantly surpassing conventional thermoelectric materials. The well-established linear relationship between the generated voltage and temperature variation enables HCA-based intelligent fire-alarm system to accurately emit continuous alerts during fire incidents and swiftly transmit alarm signals to terminal devices. The development of this intelligent fire-alarm system presents new avenues in intelligent fire-safety technologies.

Computational Study of Ground-State Destabilization Effects and Dipole-Dipole Interaction Energies in Amphidynamic Crystals.

Ground-state destabilization is a promising strategy to modulate rotational barriers in amphidynamic crystals. Density functional theory studies of polar phenylenes installed as rotators in pillared paddle-wheel metal organic frameworks were performed to investigate the effects of ground-state destabilization on their rotational dynamics. We found that as the steric size of phenylene substituents increases, the ground-state destabilization effect is also increased. Specifically, a significant destabilization of the ground-state energy occurred as the size of the substituents increased, with values ranging from 2 to 11.7 kcal/mol. An evaluation of the effects of substituents on dipole-dipole interaction energies and rotational barriers suggests that it should be possible to engineer amphidynamic crystals where the dipole-dipole interaction energy becomes comparable to the rotational barriers. Notably, while pure dipole-dipole interaction energies reached values ranging from 0.6 to 2.4 kcal/mol, the inclusion of electronic and steric effects can alter dipolar orientations to significantly greater values. We propose that careful selection of polar substituents with different sizes may help create temperature-responsive materials with switchable collective polarization.

Design and Implementation of Tilted FBG for Concurrent Temperature and Humidity Measurement using Machine Learning

Tilted Fiber Bragg Grating (TFBG) coated with humidity and temperature responsive material is proposed for simultaneous measurement of environmental parameters. Different types of materials are analyzed to optimize the coating material on the grating structure for the measurement of humidity and temperature simultaneously. The optimized coating material is used to fabricate the sensor and experimentally investigated under different humidity and temperature conditions. To further enhance the performance, machine learning algorithms such as Gaussian Progress Regression, Random Forest, K-Nearest Neighbor, AdaBoost, Gradient Boosting algorithm were trained with the spectrum data to estimate the environmental parameters simultaneously. Gradient boosting algorithm best suited for the estimation with better performance metrics of absolute error of 0.6509, RMS of 2.7412 and MAPE of 1.312 for monitoring temperature and humidity simultaneously.

Theoretical analysis of Reiner-Philippoff fluid flow in two layers due to metachronal propulsion: Subject to surrounding temperature

Mucociliary clearance plays a crucial role within the respiratory system as an initial protective mechanism against infections. Hence, it is imperative to validate any assumptions made regarding the mucociliary clearance and its impact on its functionality. This study examines flow of two-dimensional Reiner-Philippoff fluid within a ciliated channel, resulting in the separation of the fluid into two immiscible layers due to variations in viscosity. The governing equations are shortened through utilization of the long wavelength and Reynolds number (low) approximation. The impacts of emerging parameters are examined through the utilization of graphical representations. It has been observed that when there are variations in fluid properties, such as density, thermal conductivity, and viscosity between two neighboring zones, concept of a peripheral layer should be employed in order to achieve more accurate and realistic outcomes. The figures indicate that an increase in viscosities, thermal conductivities, and fluid characteristics leads to an elevation in temperature field in both layers. Moreover, the potential future scope of this study holds the promise of making substantial contributions to the comprehension of intricate fluid dynamics and fostering the advancement of novel technologies that can be practically applied across various domains. Additional research into the thermal characteristics of the system may contribute to a deeper comprehension of the complex interplay between temperature fluctuations and the dynamics of Reiner-Philippoff fluids. This has the potential to facilitate the advancement of thermal control mechanisms or the investigation of temperature-responsive materials for the purpose of manipulating fluid flow properties.

Cage-shaped self-folding mechanical metamaterials

Self-folding is an effective design method for mechanical metamaterials with complex configurations and multiple material components. However, existing self-folding mechanical metamaterials are typically limited to a single transformation, limiting their potential for various deformation modes and diverse application scenarios. In this paper, we present a cage-shaped, self-folding mechanical metamaterial. This metamaterial exhibits multiple deformation modes from an initially flat state upon heating to different temperatures and subsequently remains stable upon cooling. The constituent self-folding elements of the metamaterial comprise temperature-responsive materials to achieve different folding thresholds. Theoretical models are developed to quantify the mechanical properties of the metamaterial, enabling programmable design of its mechanical performance. We also demonstrate that the cage-shaped mechanical metamaterial has tunable mechanical properties, multi-stage load-bearing, and decoupling of mechanical performance, providing the possibility of multifunctional applications in various fields.

Nano-injectable pH/NIR-responsive hydrogel for chemo-photothermal synergistic drug delivery.

Conventional cancer treatments are highly toxic and ineffective; therefore, it is essential to develop less toxic and minimally invasive treatment methods. A pH/Near Infra-red (NIR) dual-responsive, nano-injectable smart hydrogel was fabricated by incorporating CuS nanoparticles into the hydrogel networks formed by a random copolymer of N-isopropylacrylamide (NIPAM) and double-bond functionalized uracil. Microstructural characterizations of synthesized polymer and hydrogels were carried out using transmission electron microscope (TEM), scanning electron microscope (SEM), nuclear magnetic resonance (NMR) and fourier transform infrared spectroscopy (FT-IR). Multiple hydrogen bonding interactions between uracils function as physical cross-linking points to construct the network structure of the polymeric nanogel without the addition of additional cross-linking agents, ensuring the material's safety. The amino group on the structure of uracil gives the uracil-modified polymeric hydrogel excellent pH responsiveness. Notably, as a temperature-responsive material, poly (N-isopropylacrylamide) (PNIPAM) nanogel solution can achieve in situ gel formation (within 100 s at 37°C) above its lower critical solution temperature (LCST), granting injectability to polymeric solutions. Moreover, using a hierarchical construction strategy, the variable loading of DOX and CuS was achieved. First, a heterogeneous system was created by encapsulating doxorubicin (DOX) inside the nanogel via hydrophobic and π-π stacking interactions, followed by the introduction of CuS nanoparticles as photosensitizers outside of the nanogels. Due to the presence of CuS nanoparticles, the gel is able to convert NIR light into local heat to enhance the destruction of tumor cells while simultaneously achieving rapid in situ gel formation. The in situ-forming hydrogel showed promising tissue biocompatibility. The in vitro antitumor test demonstrated the capacity of the nanocomposite hydrogel for chemo-photothermal synergistic therapy. Therefore, this prepared platform has the potential to become a safe and effective, smart-responsive drug carrier for chemotherapy and PTT synergy, a minimally invasive material for tumor treatment.

A temperature-responsive drug release system based on MoS2 nanosheets and 1-tetradecanol

The high specific surface area and photothermal ability of 2D MoS2 nanostructures have attracted a lot of attention in combined photo-chemotherapy. In this research, we synthesized PEGylated MoS2 with dispersed nanosheet morphology through a simple hydrothermal method and loaded them with Doxorubicin (DOX) as an anticancer drug (MoS2-PEG/DOX). Synthesized MoS2 nanosheets demonstrate a high drug loading capacity (DLC) of 122.2%. This is the first report of the high DLC for MoS2-PEG nanosheets synthesized with the hydrothermal method. To prevent premature drug release and increase DLC to 184%, MoS2-PEG/DOX is coated with 1-tetradecanol (TD) which is a bio-compatible temperature-responsive material (MoS2-PEG/DOX@TD). The prepared nanostructure is a dual-responsive platform that drug release can be controlled by pH and NIR irradiation. The release profile was investigated and compared at normal and acidic pH and three different conditions for each pH (body temperature, ambient mild hyperthermia temperature, and NIR irradiation). The results indicate that the most amount of DOX is released in acidic pH and hyperthermia temperature (43 ℃). NIR irradiation has an extensive effect on DOX release in comparison with hyperthermia temperature so 34.75% of the drug is released within only 30 min of laser irradiation with a power density of 1 W/cm2 in acidic pH. MTT results indicate that this nanoplatform is biocompatible. Hence dispersed MoS2-PEG nanosheets with high DLC, coated with TD for the first time, can improve the efficiency of synergistic photo-chemotherapy and can solve the problem of premature drug release from MoS2 nanosheets and release drug under controlled conditions.

Heat-Resistant and Color-Changing Luminescent Polysulfone for Information Encryption and Fire Alarming.

An intrinsic difficulty with thermally responsive photoluminescent materials is that high temperatures usually destroy luminance due to the notorious thermal quenching effect. Limited by the vulnerable chemical structure and soft skeleton, most of the existing photoluminescent responsive materials fail to indicate or work at a surging temperature over 100 °C, thus limiting application in display and alarming in harsh conditions. Herein, enlightened by chameleon's adaptive nature to external stimulus, we introduce a topologically optimized electron donor-acceptor (DA) structure and supramolecular interactions of lanthanide ions into the polymer backbone. The emission color determined by the DA structure is stable at high temperatures, and metal-ligand interaction phosphorescence is temperature-adjustable. Owing to the excellent reproducibility and heat resistance of composite films, the sensors can be bent into different three-dimensional structures and adhered to metal surfaces as flexible thermometers with superior display resolution. The polymer composite film could be directly applied as a photoluminescent quick response (QR) code, with patterns simultaneously variable to a temperature from 30 to 150 °C free of manual operation. More importantly, the polymeric composite could be in-situ-oxidized to a "sulfone" structure with an enhanced glass transition temperature of 297-304 °C. The heat- and flame-resistant characteristics of the oxidized films give rise to the application of fire alarming devices since it can locate the fire source and respond exactly depending on the distance from the fire. The unique display, encryption, and alarming functions of the polymeric composite studied in this work bring forward a new concept of developing a great information security and disaster monitoring system with the application of temperature-responsive materials.

Temperature Responsive Copolymers Films of Polyether and Bio-Based Polyamide Loaded with Imidazolium Ionic Liquids for Smart Packaging Applications

Temperature-responsive materials are highly interesting for temperature-triggered applications such as drug delivery and smart packaging. Imidazolium Ionic Liquids (ILs), with a long side chain on the cation and a melting temperature of around 50 °C, were synthetized and loaded at moderate amounts (up to 20 wt%) within copolymers of polyether and a bio-based polyamide via solution casting. The resulting films were analyzed to assess their structural and thermal properties, and the gas permeation changes due to their temperature-responsive behavior. The splitting of FT-IR signals is evident, and, in the thermal analysis, a shift in the glass transition temperature (Tg) for the soft block in the host matrix towards higher values upon the addition of both ILs is also observed. The composite films show a temperature-dependent permeation with a step change corresponding to the solid-liquid phase change in the ILs. Thus, the prepared polymer gel/ILs composite membranes provide the possibility of modulating the transport properties of the polymer matrix simply by playing with temperature. The permeation of all the investigated gases obeys an Arrhenius-type law. A specific permeation behavior, depending on the heating-cooling cycle sequence, can be observed for carbon dioxide. The obtained results indicate the potential interest of the developed nanocomposites as CO2 valves for smart packaging applications.

A sustainable process to 100% bio-based nylons integrated chemical and biological conversion of lignocellulose

Considerable progress has been made in recent years to the development of sustainable polymers from bio-based feedstocks. In this study, 100% bio-based nylons were prepared via an integrated chemical and biological process from lignocellulose. These novel nylons were obtained by the melt polymerization of 3-propyladipic acid derived from lignin and 1,5-pentenediamine/1,4-butanediamine derived from carbohydrate sugar. Central to the concept is a three-step noble metal free catalytic chemical funnelling sequence (Raney Ni mediated reductive catalytic fractionation - reductive funnelling - oxidative funnelling), which allowed for obtaining a single component 3-propyladipic acid from lignin with high efficiency. The structural and thermodynamic properties of the obtained nylons have been systematically investigated, and thus obtained transparent bio-based nylons exhibited higher Mw (>32,000) and excellent thermal stability (Td5% > 265 °C). Considering their moderate Tg and good melt strength, these transparent bio-based nylons could serve as promising functional additives or temperature-responsive materials.

Production of 100% bio-based semi-aromatic nylon by aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid with bio aliphatic diamine

The development of sustainable polymers from biomass-based feedstocks has become a hot topic in both academia and industry. In this study, aerobic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid (FDCA) catalyzed by fluorous silica gel-supported perfluoro-tagged gold nanoparticles was first reported. With the aid of this highly active catalyst, a maximum HMF conversion of 100% with 91% FDCA selectivity was achieved, and the catalyst could be used 3 times without significant loss of activity. The nylon salts 5F (1,5-pentylenediamine-FDCA) and 10F (1,10-decylenediamine-FDCA) were then prepared through crystallization, and their single crystal structures were first determined by single X-ray diffraction. Finally, 100% bio-based semi-aromatic nylon 5F and 10F were obtained by the melt polymerization of the nylon 5F and 10F salt, and their structural and thermodynamic properties have been systematically investigated. The results showed these transparent bio-based nylon materials have potential application as functional additives, temperature responsive materials or general plastics in conduits and household plastic devices.

Efficient reclamation phosphate by alginate-g-BMOF using poly(N-isopropyl acrylamide-co-acrylamide) as coating for temperature-responsive slow-release P-fertilizer

Poly(N-isopropyl acrylamide) and its derived copolymer, as a temperature-responsive material, are widely used in the field of anticancer drug carrier. And it also plays an important role as carrier in slow-release fertilizer in recent years. In this paper, a smart poly(N-isopropyl acrylamide-co-acrylamide)-coated Alg-BMOF (PABMOF) was fabricated in ionic liquids microemulsion ([Bmim]PF6/TX-100/water) as nano-reactor. The structure and morphology of PABMOF were characterized by FT-IR, XRD, XPS, SEM, TG and BET. The resultant PABMOF was used as a adsorbent for H2PO4− adsorption. The adsorption kinetics, isotherms and mechanism of H2PO4− onto the resultant PABMOF were studied. The adsorption kinetic data was well suitable for pseudo-second-order kinetic model, and adsorption isotherm results demonstrated that the equilibrium data was fitted for Freundlich model. The water-holding and water-retention capacity of soil with TRSRFs addition of 2 wt% were74.3% and 52.13% at 30th day, respectively. Moreover, the release behavior of TRSRFs in water show that the cumulative release rate (Cr%) were 81.4% at 45 °C and 97.6% at 25 °C within 172 h, which displayed the excellent temperature-responsive property. The effect of TRSRFs on the growth of Chinese cabbage was investigated, which was indexed with the germination rate, plant height and root length of the crop.

Temperature-Responsive Nanoparticles Enable Specific Binding of Apolipoproteins from Human Plasma.

Apolipoproteins are an important class of proteins because they provide a so-called stealth effect to nanoparticles. The stealth effect on nanocarriers leads to a reduced unspecific uptake into immune cells and thereby to a prolonged blood circulation time. Herein, a novel strategy to bind apolipoproteins specifically on nanoparticles by adjusting the temperature during their incubation in human plasma is presented. This specific binding, in turn, allows a control of the stealth behavior of the nanoparticles. Nanoparticles with a well-defined poly(N-isopropylacrylamide) shell are prepared, displaying a reversible change of hydrophobicity at a temperature around 32°C. It is shown by label-free quantitative liquid chromatography-mass spectrometry that the nanoparticles are largely enriched with apolipoprotein J (clusterin) at 25°C while they are enriched with apolipoprotein A1 and apolipoprotein E at 37°C. The temperature-dependent protein binding is found to significantly influence the uptake of the nanoparticles by RAW264.7 and HeLa cells. The findings imply that the functionalization of nanoparticles with temperature-responsive materials is a suitable method for imparting stealth properties to nanocarriers for drug-delivery.

Recent Advances in Antiinflammatory Material Design.

Implants and prostheses are widely used to replace damaged tissues or to treat various diseases. However, besides the risk of bacterial or fungal infection, an inflammatory response usually occurs. Here, recent progress in the field of anti-inflammatory biomaterials is described. Different materials and approaches are used to decrease the inflammatory response, including hydrogels, nanoparticles, implant surface coating by polymers, and a variety of systems for anti-inflammatory drug delivery. Complex multifunctional systems dealing with inflammation, microbial infection, bone regeneration, or angiogenesis are also described. New promising stimuli-responsive systems, such as pH- and temperature-responsive materials, are also being developed that would enable an "intelligent" antiinflammatory response when the inflammation occurs. Together, different approaches hold promise for creation of novel multifunctional smart materials allowing better implant integration and tissue regeneration.

Advances and challenges for fluorescence nanothermometry.

Fluorescent nanothermometers can probe changes in local temperature in living cells and in vivo and reveal fundamental insights into biological properties. This field has attracted global efforts in developing both temperature-responsive materials and detection procedures to achieve sub-degree temperature resolution in biosystems. Recent generations of nanothermometers show superior performance to earlier ones and also offer multifunctionality, enabling state-of-the-art functional imaging with improved spatial, temporal and temperature resolutions for monitoring the metabolism of intracellular organelles and internal organs. Although progress in this field has been rapid, it has not been without controversy, as recent studies have shown possible biased sensing during fluorescence-based detection. Here, we introduce the design principles and advances in fluorescence nanothermometry, highlight application achievements, discuss scenarios that may lead to biased sensing, analyze the challenges ahead in terms of both fundamental issues and practical implementations, and point to new directions for improving this interdisciplinary field.

Gas responsive cellulose fibers for capturing and releasing of dyes and proteins from water by packing a smart separation column

Separation of dyes and proteins from water remains a significant challenge. Common absorbents without recyclability might bring secondary pollutions, which may be avoided by developing stimuli-responsive smart absorbents. Here in this work, a CO2-responsive polymer poly(2-(dimethylamino) ethyl methacrylate) was grafted from cellulose fibers (Cell-g-PDEA). The chemical structure and surface morphology were confirmed with nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction and scanning electron microscope. The CO2-sensitivity was demonstrated by monitoring the pH, surface Zeta potential and dispersed appearance under stimulus of CO2. Furthermore, the modified cellulose fibers were packed into a syringe to construct a smart separation column that reversibly captured and released anionic dyes and proteins from water under gas stimulus. Comparing with traditional pH or temperature responsive materials, the CO2-responsive cellulose fibers take the advantages on energy-saving, good reversibility and moderate running conditions, thus might find applications in smart separations, clinical diagnose and therapies.

Mechanism of the temperature-responsive material regulating porous morphology on epoxy phenolic novolac resin microcapsule surface

Porous microcapsules (MCs) with tailorable surface morphology are indispensable in practical applications because of their large surface area and controlled release. In this study, epoxy phenolic novolac resin MCs were prepared with temperature-responsive 2,4,6-tris(dimethylaminomethyl)phenol (DMP) as crosslinker. Reaction temperature was proved to generate distinct effects on MC porous morphology, shell thickness, mechanical strength and release behavior. The MC surface varied from nonporous to dense small pores (ca. 237 nm in diameter) with increasing temperature from 40 °C to 70 °C, but they showed decreasing tendency at higher temperature (＞70 °C). The encapsulation process illuminated that DMP aggregates formed and deposited on the loose shells at 60 °C and 70 °C (close to the so-called cloud point (Tscp) of DMP), leading to porous morphology. Nevertheless, at temperature far below or above the Tscp of DMP (＜50 °C or ＞70 °C), DMP kept its solubility in water or insufficiently deposited on the shells, which resulted in no pores existed. Higher temperature promoted the reactivity to generate thicker shells and larger mechanical strength, further leading to prolong payload release. The present work provided an insight about the reaction temperature to prepare tunable MCs, which can be employed to encapsulate lipophilic components in agriculture field.

Three-Dimensional Metal-Free Molecular Perovskite with a Thermally Induced Switchable Dielectric Response.

Temperature-responsive materials with switching physical properties have been widely researched. Among them, the switchable dielectric perovskite materials show potential applications in the electrical and electronic industries and even the intelligence industries. However, perovskite oxides and hybrid organic-inorganic perovskites, as the most representative switchable dielectric materials, are limited by bad biocompatibility. Herein, we report temperature-dielectric-responsive metal-free perovskite (H2dabco)(NH4)[BF4]3 constructed by the strategy of substituting the B site in the general formula ABX3 (doubly protonated 1,4-diazabicyclo[2.2.2]octane = H2dabco). Meanwhile, structurally similar hybrid material (H2dabco)Rb[BF4]3 was designed as a control. They exhibit similar phase-transition characteristics and dielectric response behaviors around 333 K. More interestingly, the ordered-disordered transformation of their organic "spherical" cations (H2dabco) was deemed to produce their phase transitions and dielectric response switching. Given its ability to generate a dielectric response, (H2dabco)(NH4)[BF4]3 will show the potential application of metal-free perovskite in a future thermal sensing device.

Thermo-sensitive gellan maleate/N-isopropylacrylamide hydrogels: initial “in vitro” and “in vivo” evaluation as ocular inserts

Hydrogels are among the most used polymer–drug systems, polysaccharide-based materials presenting many advantages to be used for controlled release applications. Gellan maleate/NIPAm hydrogels are hydrophilic swelling matrixes that were originally developed for biomedical applications as controlled release dosage forms. The purpose of this study is to explore the ability of gellan maleate/NIPAm thermoreversible hydrogels for ophthalmic applications as ocular inserts. Studied hydrogels were synthesized by free radical grafting/polymerization of unsaturated esters (gellan maleate) with N-isopropylacrylamide (NIPAm) and N,N′-methylenebisacrylamide as cross-linker. They are evaluated for swelling degree, in vitro inclusion and release of drugs (adrenaline and chloramphenicol) and in vivo biocompatibility. The hydrogel is shown to be a temperature-responsive material with a LCST close to 36 °C. The swelling properties and the release of biologically active compounds occur when polymer conformation changes determining phase transition at LCST. Gellan-based hydrogels present reproducible responses to alternation between ambient temperature and human body one. The stability and biocompatibility were evaluated in vitro and in vivo. Tissue response to implantation of hydrogel was determined by histological analysis (haematoxylin–eosin–methylene blue and periodic acid–Schiff). A thin fibrous capsule was observed around the implanted hydrogels. No necrosis, calcification and acute inflammatory reaction were noted. Successful preliminary results were obtained for ophthalmic applications.