Thermal Response Properties Research Articles

A fermion phenomenology of low-temperature strongly-noncrystalline solids

Insisting on the relevance of spin-statistics theorem, I propose that anomalous low-energy excitations (LEEs) of strongly-noncrystalline solids (SNSs), observed at low temperatures T<1K, are fermions, which are localized and weakly interacting. This phenomenological theory rationalizes all low-energy quantum many-body states of SNSs as Goldstone bosons-phonons and half-integer-spin fermions. Fermi glass of LEEs, rather than statistical ensemble of isolated two-level systems, appears to be a consistent theory of various thermal and nonlinear response properties of SNSs. A robust consequence of the theory is nearly constant-in-energy density of fermion states near Fermi energy, which in turn implies linear-in-temperature specific heat and dimensionless frequency-independent sound absorption. Consistent parameters of Fermi glass are estimated from theoretical scaling arguments as well as directly from experimental data.

Tunable paclitaxel release carrier using diselenide-disulfide balance as regulator

There are many reasons that lead to the failure of cancer chemotherapy, such as uncontrolled drug release, low drug utilization, and severe side effects. To overcome these obstacles, two kinds of thermal and redox-responsive copolymers with multiple diselenide/disulfide linkages, polyethylene glycol -alt- diselenodipropionate/disulfhydryldipropionate-b-poly(N-isopropylacrylamide) (abbreviated as PEG-alt-DSeDP-b-PNIPAM and PEG-alt-DSDP-b-PNIPAM) were fabricated by alternative esterification and following atom transfer radical polymerization. Afterward, these prepared copolymers were mixed in line with the mass ratio of 8:0, 5:3, 3:5, 0:8 (denoted as S1, S2, S3, and S4, respectively), and self-assembled with paclitaxel (PTX) to obtain PTX-loaded S1, S2, S3, and S4 nanomicellar assemblies, aiming to realize PTX tunable release using diselenide-disulfide balance as regulator. The chemical structures of these two copolymers were characterized by gel permeation chromatography, indicating eight diselenide/disulfide linkages and eight PEG units were contained in these copolymers. Moreover, the thermal-responsive property was detected by UV–vis spectroscopy, meanwhile, the redox responsiveness was observed by TEM in the presence of 10 mM glutathione. We found that 76.90% of PTX was released from S1 nanomicelles within 23 h. In contrast, this percentage decreased to 64.53% for S4 nanomicelles even the incubation time prolonged, indicating explosive and slow release behaviors of S1 and S4 nanomicelles, respectively. In addition, gradually decreased fluorescence intensity around the cellular nucleus was occurred from S1 to S4 orderly, which was consistent with cellular uptake and in vivo anti-tumor experiments. Taken together, this work not only provides a strategy for tunable PTX release, but also improves effectiveness of PTX in cancer treatment.

Molecular Thermal Motion Modulated Room-Temperature Phosphorescence for Multilevel Encryption.

The stimulus-responsive room-temperature phosphorescence (RTP) materials have become an increasingly significant topic in the fields of bioimaging, sensing, and anticounterfeiting. However, this kind of materials is scarce to date, especially for the ones with delicate stimulus-responsive behavior. Herein, a universal strategy for multilevel thermal erasure of RTP via chromatographic separation of host-guest doping RTP systems is proposed. The tunable host-guest systems, matrix materials, heating temperature, and time are demonstrated to allow precise six-level data encryption, QR code encryption, and thermochromic phosphorescence encryption. Mechanistic study reveals that the thermal-responsive property might be attributed to molecular thermal motion and the separation effect of the silica gel, which provides expanded applications of host-guest RTP materials such as cold chain break detection. This work offers a simple yet universal way to construct advanced responsive RTP materials.

Thermal insulation and anti-vibration properties of MoSi2-based coating on mullite fiber insulation tiles

Thermal protection materials with excellent thermal insulation properties and high reliability are crucial for aerospace vehicle. Mullite fiber insulation tiles coated with MoSi2-borosilicate glass ([email protected]2) were prepared by a simple slurry method. Results shown that the surface temperature rapidly reached 1043.1 °C under the heat flux of 450 kW/m2, while the cold-surface remained at room temperature. The adjusting effects of MoSi2-based coating on the thermal response and transfer properties of MFIT were investigated systematically. Compared with MFIT, the surface and internal temperatures of [email protected]2 were obviously suppressed, due to the existence of MoSi2-based coating with high emissivity, which effectively enhanced the thermal radiation of the surfaces. Finally, the structural reliability under coupled environment of heating (q0 = 450 kW/m2) and random vibration with high magnitude (20–2000 Hz, Grms = 20 g) was also investigated. Destructive cracking and peeling of the coating were not observed, due to the excellent bonding strength between the coating and the substrate. The results provided an important basis for the potential application of insulation tiles with mullite fibers in aerospace vehicles and the design of lightweight thermal protection systems.

Preparation of high‐efficient ethylene‐vinyl acetate‐based thermal management materials by reducing interfacial thermal resistance with the assistance of polydopamine

AbstractThe rapid development of electronic technology puts forward higher requirements for thermal management materials. In this paper, polydopamine (PDA) was employed to improve the interfacial interaction between filler and matrix, and then to further regulate the interfacial thermal resistance and thermal conductivity of ethylene‐vinyl acetate (EVA) composites. It was found that boron nitride (BN) sheets and carbon nanotubes (CNTs) can fully exert the synergistic heat conduction effect with the assistance of PDA, and construct continuous and efficient heat conduction channels in EVA matrix. When 30 vol% BN and 2 vol% CNTs were added, the in‐plane thermal conductivity of the composite reached 9.61 W·m−1·K−1, which was about 3225% higher than that of EVA matrix. The contribution of PDA to auxiliary enhanced thermal conductivity was further verified by the fitting and calculation of the interfacial thermal resistance of the composites. In addition, the EVA composite material had sensitive thermal response and stable electrical insulation properties, which ensured its thermal management applications in electronic equipment.

Calcium Carbonate as Functional Filler in Polyamide 12-Manipulation of the Thermal and Mechanical Properties

Adjusting the thermal response properties of a polymeric compound can significantly improve the usability in a selective laser-sintering process. As previously shown, combining a precise amount of coarse and narrow size distribution fine calcium carbonate fillers results in a potential optimization of the thermal properties of a polyamide 12 matrix. Additionally, up to 60% of the normally associated lost ductility can be re-gained by surface modification, thus functionalizing the filler. To optimize the functionality further this study combines a precisely defined particle size ratio of fillers adopting a specially selected surface modification using amino hexanoic acid. Morphology of the carbonate filler was also investigated. The range of effect of each parameter on the thermal response and mechanical properties was studied. The results show that the thermal properties have large potential to be optimized, without reducing the ductility significantly, by adjusting the morphology and size ratio of coarse and fine filler particles. The compound properties were demonstrated using a twin-screw extruder, indicating the potential for producing a preparate composite for additive manufacturing.

Effect of film types on thermal response, cellular structure, forming defects and mechanical properties of combined in-mold decoration and microcellular injection molding parts

Different types of polymer films were used in the combined in-mold decoration and microcellular injection molding (IMD/MIM) process. The multiphase fluid-solid coupled heat transfer model was established to study the thermal response at the melt filling stage in the IMD/MIM process. It was found that the temperature distributed asymmetrically along the thickness direction due to the changed heat transfer coefficient of the melt on the film side. When polyethylene terephthalate (PET) films were applied, the temperature of the melt-film interface increased faster and to be higher at the end of melt filling stage in comparison with the application of polycarbonate (PC) and thermoplastic polyurethane (TPU) films. And the effects of film types on the cellular structure, forming defects and mechanical properties of IMD/MIM parts were also studied experimentally. The results showed that the film types had no obvious effect on the cells size in the transition layer and the mechanical properties of the parts. Under certain film thickness, the offset distance of core layer was the largest with PET film used, while the offset distance was the smallest with TPU film used. And similar results were found for the warpage of the parts. However, an exactly opposite change occurred for the thickness of film-side transition layer and the bubble marks on the surface of the parts.

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Multistimuli-Responsive Fluorescent Organometallic Assemblies Based on Mesoionic Carbene-Decorated Tetraphenylethene Ligands and Their Applications in Cell Imaging

Impact of Bimodal Particle Size Distribution Ratio of Functional Calcium Carbonate Filler on Thermal and Flowability Properties of Polyamide 12

In previous investigations, it was shown that the melting, as well as crystallization behavior of polyamide 12, could be manipulated by adjusting the particle size distribution of calcium carbonate as a functional filler. It was demonstrated that the melt properties of this compound show a significant dependency on the filler volume-based particle size. As finer and narrower the calcium carbonate particles in the polymer matrix become, the less influence the filler has on the melting properties, influencing the melt flow less significantly than the same surface amount of broad size distribution coarse calcium carbonate filler particles. However, due to increased nucleation, the crystallization behavior on cooling showed a markedly more rapid onset in the case of fine sub-micrometer filler particle size. To control further and optimize the thermal response properties of a filling compound for improved properties in additive manufacturing processing through selective laser sintering, the possibility to combine precisely defined particle size distributions has been studied, thereby combining the benefits of each particle size range within the chosen material size distribution contributes to the matrix. The melt flow at 190 °C, the melting speed, melting and crystallization point as well as crystallization time at 170 °C were analyzed. The thermal and flow properties of a polyamide 12 matrix can potentially be optimized with a combination of a precise amount of coarse and fine calcium carbonate filler. The improvements were exemplified using a twin-screw extruder for compounding, indicating the potential for optimizing functionally filled polymer in additive manufacturing.

Hetero-network hydrogels crosslinked with silica nanoparticles for strategic control of thermal responsive property.

Two thermoresponsive copolymers with different lower critical solution temperatures (LCSTs) were crosslinked using silica nanoparticles to afford hybrid hydrogels exhibiting two distinct thermo-responsivities. The thermo-responsive copolymers were synthesised by free radical polymerisation from a monomer with a reactive side chain (3-methacryloxypropyl trimethoxysilane (S)) and water-soluble monomers with different thermo-responsivities (N-isopropyl acrylamide (N) or N-(3-methoxy propyl)acrylamide (M)). The obtained reactive copolymers, poly(N-isopropyl acrylamide-co-3-methacryloxypropyl trimethoxysilane) (pNS) and poly(N-(3-methoxy propyl acrylamide-co-3-methacryloxypropyl trimethoxysilane)) (pMS), were characterized by multiple techniques including 1H NMR and FTIR spectroscopy. The hetero-network hybrid hydrogels were easily prepared by mixing aqueous solutions of the copolymer with an aqueous colloidal silica suspension; their gelation properties could be tuned by varying the amounts of pNS, pMS, and Si. Differential scanning calorimetric analysis showed that the hetero-network hydrogel exhibited a critical two-step phase transition at temperatures around the LCST of each copolymer (33 °C for pNS, 73 °C for pMS), indicating that each polymer does not disturb the phase transitions of the other. The deswelling of the hetero-network hydrogel could be controlled with respect to temperature and time.

New Insights into Cutaneous Laser Stimulation – Dependency on Skin and Laser Type

Cutaneous laser stimulation is a proficient tool to investigate the function of the nociceptive system. However, variations in laser–skin interactions, causes by different skin anatomies and laser wavelength, affects the robustness of nociceptor activation. Thus, thoroughly understanding how the skin is heated by a laser pulse is important to characterize the thermal response properties of nociceptors. The study aim was to investigate how skin type and laser wavelength influences nociceptor activation during laser stimulation. Ten healthy subjects were exposed to brief CO2 (low skin penetrance) and Nd:YAP (high skin penetrance) laser stimuli delivered to the dorsum and palm of the hand, using three different intensities. Reaction times and perception intensities were recorded. A computational model simulated heat transfer in the skin and nociceptor activation in different skin types across different wavelengths and intensities. Intensity ratings were significantly lower and reaction-times significantly increased for CO2 laser stimuli in the palm compared to the dorsum. This was not the case for Nd:YAP laser stimuli. The computational model showed that these differences can be explained by the different skin absorption of CO2 and Nd:YAP lasers. For CO2 laser stimuli, the thicker stratum corneum of the glabrous skin reduces nociceptor activation, whereas the high penetrating Nd:YAP laser elicits a similar nociceptor activation, irrespective of skin type. Nociceptor activation during laser stimulation highly depends on skin composition and laser wavelength, especially for lasers having a low penetrance wavelength. A computational model showed that this difference could be explained primarily due to differences in skin composition.

Structure-controlled zwitterionic nanocapsules with thermal-responsiveness

A facile approach is established to prepare zwitterionic nanocapsules (ZNCs) with controlled diameters and core/shell structures based on an inverse reversible addition-fragmentation transfer (RAFT) miniemulsion interfacial polymerization method. The diameters and core volume fractions of ZNCs can be tuned finely from 61 to 220 nm and from 0.22 to 0.61, respectively. Furthermore, the thermal-responsive property of the prepared zwitterionic nanocapsules was systematically studied relating to core/shell ratios and cross-linking degrees. These ZNCs could be particularly useful in constructing polymeric materials with well-defined nanoporous structures for nano-void membranes, drug delivery devices and catalytic carriers.

High water permeating thin film composite polyamide nanofiltration membranes showing thermal responsive gating properties

High water permeating thin film composite (TFC) polyamide (PA) nanofiltration (NF) membranes were prepared by grafting 2-(Dimethylamino)ethyl methacrylate (DMAEMA) monomers onto their surfaces through a free radical polymerization process. Grafted PDMAEMA layer increased the water permeation of TFC-PA NF membranes up to 2.6 times without trading off their salt rejection capability. The anti-fouling performance of the NF membranes was improved by further surface zwitterionization processes involving 1,3-propane sulfone(1,3-PS). Thermal-responsive gating property for water and salt permeation was observed in these high flux NF membranes and found to be useful in trapping and releasing protein molecules via temperature variations. These high flux NF membranes with thermal-responsive gating property may find applications in material enrichment, drug delivery and water treatments.

Nanocomposite Polymer Hydrogels Reinforced by Carbon Dots and Hectorite Clay

Herein, two nanoparticles with different dimensions, spherical carbon dots (C-dots) and sheetlike hectorite clay, were used as physical crosslinkers to fabricate C-dots-clay-poly(N-isopropylacrylamide) nanocomposite hydrogels (coded as C-dots-clay-PNIPAm hydrogels). The mechanical properties, fluorescence features and thermal-responsive properties of the C-dots-clay-PNIPAm hydrogels were evaluated. The experimental results indicate that synergistic effects of C-dots and hectorite clay nanoparticles are able to significantly enhance mechanical properties of the hydrogels. The hydrogels can be stretched up to 1730% with strength as high as 250 kPa when the C-dots concentration is 0.1wt% and the clay concentration is 6wt%. The hydrogels exhibit complete self-healing through autonomic reconstruction of crosslinked network a damaged interface. The hydrogels show favorable thermal-responsive properties with the volume phase transition around 34 °C. In addition, the hydrogels are endowed with fluorescence features that are associated with C-dots in the hydrogels. It can be expected that the as-fabricated C-dots-clay-PNIPAm hydrogels are promising for applications in sensors, biomedical carriers and tissue engineering.

4D Printing of High-Performance Thermal-Responsive Liquid Metal Elastomers Driven by Embedded Microliquid Chambers.

Four-dimensional (4D) printing of swellable materials have been viewed as an ideal approach to build shape morphing architectures. However, there is less variety in high-performance swellable materials, limiting its development. To address this challenge, we proposed a new strategy for designing high-performance thermal-responsive swellable materials. The reversible liquid-vapor phase change of embedded low boiling point liquid chambers and functional liquid metal fillers endows the designed elastomer with the reversible thermal-responsive swellable property with high stability, fast response speed, and large equilibrium deformation. Notably, liquid metal fillers play a crucial role in improving the thermal-responsive property via improving the thermal conductivity and fracture toughness and decreasing the stiffness. To demonstrate the feasibility of constructing shape morphing architectures with proposed thermal-responsive liquid metal elastomers, typical bilayer structures were printed and investigated. By altering the key design parameters, the response speed and equilibrium deformation can be adjusted as needed. Therefore, complex shape morphing architectures can be printed. This study could provide a new avenue to design swellable material systems for 4D printing of shape morphing architectures.

The role of conductivity and molecular mobility on the photoanisotropic response of a new azo-polymer containing sulfonic groups

We report the preparation of a new light-responsive side-chain terpolymer containing azobenzenes, as chromophoric components, sulfonic groups, as polar components, and methacrylate groups, as film forming components, and we provide a detailed characterisation of its thermal parameters, photoanisotropic character, dielectric response and optoelectronic properties. The poly[(4-methoxyazobenzene -4′-oxy) methacrylate]-co-poly[2-acrylamido-2-methyl-1-propanesulfonic acid]-co-poly[methyl methacrylate], MeOAzB/AMPS/MMA, was prepared by radical copolymerisation, possesses high thermal stability and is amorphous. Its high glass transition (Tg = 151 °C) is explained by steric effects (induced by the bulky azobenzenes) and hydrogen bonding (promoted by the polar sulfonic groups) near the polymeric backbone, which may also reduce the photoanisotropic efficiency. The transition between the energy levels of the azobenzenes (MeOAzB) in the terpolymer is controlled by p-type conductivity, and can be associated to motions in the side-chains containing the sulfonic groups (AMPS), which are locally activated below the MeOAzB/AMPS/MMA glass transition.

Thermal response properties and surface insulation failure mechanism of epoxy resin under arc ablation

Arc ablation during the operation of HVDC circuit breakers can cause irreversible damage to the epoxy resin (EP) insulation pull rod. This is one of the critical factors that affect the reliability and lifetime of a HVDC circuit breaker. In this work, we built an arc ablation experimental platform and studied the thermal response properties of EP insulation under arc ablation. The surface charge evolution characteristics and the dielectric properties were analyzed to reveal the underlying surface insulation failure mechanism of EP after arc ablation. The results indicate that arc ablation can cause severe carbonization to EP insulation. With increasing arc duration, the EP gradually transforms into carbide and pore products. Arc ablation can decrease the molecular moment orientation polarizability and the relative dielectric constant of EP insulation, and thereby increasing the current density formed by Schottky injection. Therefore, when the external electric field is applied, the charge on EP insulation surface migrates from high voltage electrode to the ablating area, causing the regional accumulation of surface charge and the formation of local failure area. This can decrease the surface electrical performance of EP insulation and lead to insulation failure finally.

Programmable stimuli-responsive polypeptides for biomimetic synthesis of silica nanocomposites and enzyme self-immobilization

Bioinspired silicification is an attractive route for achieving unique silica nanocomposites. Herein, a novel, facile and inexpensive route for biosilica synthesis is developed using the stimuli-responsive elastin-like polypeptide (ELP). The ELP is precisely tailored to a silica-mineralizing peptide by programming it with lysine residues. The resulting cationic ELP[KV8F-40] is purified in ultrahigh yield using a chromatography-free ITC purification technique based on thermal-responsive property. Excitingly, the specific activity of ELP is 40-fold higher than that of silaffin. Besides, efficient and strong entrapment of ELP is achieved with over 98% of immobilization yield and less than 2% of leakage. These imply that cationic ELP may be used as a bifunctional tag (purification and immobilization) for fusion protein. An enzyme (xylanase) is therefore chosen to genetically fuse to ELP. The ELP-fused xylanase is purified by ELP with high purity (~98%) and enables the rapid (within minutes) self-immobilization. The immobilization yield was greater than 95%, and the immobilized xylanases hardly leaked from the silica matrix, demonstrating high efficiency of the self-immobilization process. The strategy developed here may provide a new opportunity for fabricating functional silica nanocomposites in a feasible and inexpensive pathway, which will have great potentials in the field of biotechnology.

Design, fabrication and thermal performance of a novel ultra-thin vapour chamber for cooling electronic devices

In this work, a novel vapour-liquid channel-separated ultra-thin (0.4-mm-thick) vapour chamber fabricated via etching and diffusion bonding was designed for cooling electronic devices. The heat performance of ultra-thin vapour chamber was tested under five states, and micropillar arrays were etched into the chamber to study their effect on heat transfer. Additionally, infrared thermal imaging was performed to investigate the heat dissipation of cooling modules with and without the ultra-thin vapour chamber. The maximum heat transfer capacity of the ultra-thin vapour chamber in the horizontal state was 4.50 W, and the temperature difference was 4.75 °C. The experimentally measured values were very close to the theoretical capillary limit. Under normal and reverse gravities, the maximum heat transfer capacity changed by less than 11%. The effective thermal conductivity of the ultra-thin vapour chamber was 12000 W/(m·K), which is 30 times higher than that of pure copper. The cooling module with the ultra-thin vapour chamber exhibited better heat dissipation, thermal uniformity and thermal response properties. When the heating input power was 6 W, the heating block temperature, maximum surface temperature difference and equilibrium time of the cooling module with the ultra-thin vapour chamber were 8%, 54% and 32% lower, respectively, than those of the module without the ultra-thin vapour chamber. The proposed cooling solution is promising for heat dissipation problems in high-power portable electronic devices.

Influence of Mg doping on the structural, morphological, optical, thermal, and visible-light responsive antibacterial properties of ZnO nanoparticles synthesized via co-precipitation

Mg-doped zinc oxide (Zn1-xMgxO, where x = 0.000, 0.001, 0.003, 0.005, and 0.010 M) nanoparticles (MgZnO NPs) were synthesized via a co-precipitation method and subjected to various analyses for application as functional additives in food packaging. The MgZnO NPs were successfully formed at approximately 360 °C and showed an increase in the optical band gap with respect to the increase in the concentration of Mg doping. The X-ray diffraction and scanning electron microscopy analyses of MgZnO NPs confirmed the formation of hexagonal wurtzite structure and rod-like morphology. X-ray photoelectron spectra revealed that the Mg (1s) peaks centered at 1303.35 and 1303.38 eV were ascribed to the presence of Mg2+ replacing Zn2+. Transmission electron microscopy images showed rod shapes with the length of 208–650nm and width of 84–142 nm. Various concentrations of synthesized MgZnO NPs were investigated against a gram-negative (Escherichia coli - DH5α) bacterial strain under light and dark conditions. Among the studied samples, 0.010 M MgZnO NPs of concentration 3 mg/mL showed the best antibacterial activity under the light condition. MgZnO NPs revealed uneven ridges on the outer surface, which promote the diffusion ability of Zn2+ and increased production of reactive oxygen species, and consequently lead to bacterial lysis. Furthermore, this study demonstrates excellent feasibility for the application of MgZnO NPs as fillers with good antibacterial activity, especially in antimicrobial food packaging applications.