Colloid and Polymer Science最新文献

This study explores the thermomechanical properties of polymethacrylate-based shape memory polymers (SMPs), focusing on hot water as a thermal stimulus for shape recovery. Using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), the research evaluates thermal transitions, viscoelastic behavior, and energy dissipation. DSC identified a glass transition temperature (Tg) of 67 °C, critical for shape recovery. DMA revealed significant changes in storage modulus, loss modulus, and energy dissipation with varying temperature and frequency. Notably, the storage modulus increased from 3.8 × 10⁶ Pa at 10 Hz to 1 × 10⁷ Pa at 90 Hz near Tg, validating the time–temperature superposition principle. The material also showed asymmetric hysteresis behavior near Tg, indicating enhanced energy dissipation. Hot water at 67 °C was highlighted as an effective external trigger, enabling reversible deformation and improved durability. Cyclic tests identified a stability threshold, beyond which increased hysteresis and energy dissipation indicate unstable deformation. These findings advance understanding of SMP behavior under thermal and mechanical stress and demonstrate their potential in soft robotics, biomedical devices, and adaptive structures.

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An approximate expression is derived for the sedimentation potential (field) in a dilute suspension of weakly charged spherical liquid drops dispersed in an electrolyte solution under gravity, where the drop surface charge arises from ion adsorption. The derivation is based on the electrophoresis theory for liquid drops developed by Baygents and Saville, which accounts for the Marangoni effect induced by interfacial tension gradients. A simplified case is considered, in which no ions are present inside the drops. The result demonstrates that the Onsager relation between sedimentation and electrophoresis is satisfied in the present system.

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The formation of polyurethane rigid (PUR) foams is a complex process involving multiple interrelated chemical and physical mechanisms. One critical parameter for thermal insulation applications is the pore size, which has been shown to be reduced by adding fluorocarbons (FCs) to the foam formulation. While recent studies confirm this phenomenon, the underlying physico-chemical mechanisms remain unclear. In this study, we employ cryogenic scanning electron microscopy (Cryo-SEM) to investigate the evolution of nascent PUR foams and the role of FCs in shaping their morphology. Two PUR foam systems—a simplified “scientific system” and an industrially relevant “technical system”—were analysed under both laboratory and pilot-scale conditions. Our results confirm a recently formulated hypothesis that FCs impact foam structure primarily by increasing the number of entrained gas bubbles which act as heterogeneous nucleation sites. We also put in evidence the formation of interfacial FC films around the bubbles, which may affect foam stabilisation and growth dynamics. Additionally, we observe an unexpected stagnation in bubble growth in the presence of FCs, highlighting the need for further investigations. This study provides new insights into the role of FCs in pore size control and may contribute to finding alternative additives for PUR foam formulations with enhanced thermal insulation performance.

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Polymer brushes carrying poly(ethylene oxide), PEO, or poly(styrene oxide), PStO, branches along with brushes containing both PEO and PStO side chains were prepared via anionic ring opening and ring opening metathesis, ROMP, polymerization techniques, and the macromonomer methodology. The polymers were characterized by size exclusion chromatography, SEC, and NMR spectroscopy, revealing that well-defined polymeric products were obtained. These brushes were blended with linear PEO samples of different molecular weights and were studied employing differential scanning calorimetry, DSC; thermogravimetric analysis, TGA; and differential thermogravimetry, DTG, methodologies. The composition of the blend in polymer brushes, the chemical nature of the brush, and the macromolecular architecture were tested to verify their effect on the degree of crystallinity and the melting point of the linear PEO samples. These results will enhance our knowledge on how possible it is to manipulate the crystallinity of PEO and at the same time improve the mechanical properties, opening a new route for future applications.

Polymer matrix composites (PMCs) hold a prominent position in the materials field due to their exceptional mechanical strength and low weight. Epoxy resins are the PMCs that are most frequently used. By employing fillers, the properties of epoxy resins can be enhanced. In this work, we synthesized titanium dioxide (TiO₂) using the solution combustion method and employed it as a filler material. Silane-treated TiO₂ creates a better material with enhanced properties of mechanical, thermal, and barrier properties, which makes it useful in applications like protective coatings and adhesives. We then investigated the effect of this filler material on the compressive and tensile characteristics of Araldite LY556 slabs by varying the loading of titanium dioxide powder in the epoxy matrix from 0 to 2.5 wt%. The mechanical characteristics of the nanocomposites were improved due to the loading of titanium dioxide. Using scanning electron microscopy (SEM) analysis, the dispersion of filler materials in the epoxy matrix has been fully analyzed, and the presence of filler materials in the epoxy matrix has been examined using X-ray diffraction (XRD). Micromechanical models were also used to investigate the nanocomposites. The tensile strength and modulus curves for the examined polymer composite, which were computed using an analytical model, agreed well with the results obtained from experiments. For tensile strength values, the models that were examined are Nicolais–Narkis, Turcsanyi, Piggot–Leidner, and Nielsen models; for tensile modulus, the models that were reviewed are Halpin–Tsai, Kerner, and Sato–Furukawa models. The stiffness of nanocomposites was also predicted by these micromechanics models. At 2.5 wt% loading of TiO₂, the values of compressive and tensile strength have risen by more than 120%.

Polyaniline (PANI) is a well-known conducting polymer recognized for its tunable electrical conductivity and structural versatility. In this work, DBSA-doped PANI–PVC composites were synthesized using inverse emulsion polymerization to improve their physicochemical and electrochemical properties. The composites were characterized using ultraviolet–visible (UV/Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). UV/Vis spectra confirmed the emeraldine salt (ES) form of PANI, indicating successful doping and integration within the PVC matrix, while FTIR supported the incorporation of DBSA as a dopant. Electrical conductivity increased with decreasing PVC content, with optimal performance observed at 3% PVC. XRD patterns suggested reduced compatibility between PANI and PVC at higher PVC concentrations. SEM images of the DBSA/PANI-PVC 3% composite showed a rough, compact, and porous morphology, in contrast to the smooth surface of pure PANI. TGA results indicated enhanced thermal stability of the DBSA/PANI-PVC 3% composite compared to pure PANI. Cyclic voltammetry (CV) at various scan rates and concentrations demonstrated improved electrochemical sensing performance of the DBSA/PANI-PVC 3% composite, highlighting its potential for use in ascorbic acid (AA) detection.

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Cancer remains a leading cause of mortality worldwide, necessitating the development of innovative and biocompatible therapeutic platforms. This study was motivated by the need to create a multifunctional hydrogel that combines natural polymers and metal–organic frameworks for enhanced anticancer efficacy without external drug loading. Accordingly, a novel composite hydrogel was synthesized using oxidized chitosan, fish collagen peptides, and iridium-based metal–organic frameworks (Ir-MOF). The structure and properties of the hydrogel were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), and X-ray diffraction (XRD) analyses, revealing a high-specific surface area (37 m²/g), nanoscale crystallite size (79 nm), and thermal stability up to 200°C. Biological evaluation against MCF-7 breast cancer cells demonstrated significant cytotoxicity, with an IC₅₀ of 156 μg/mL and 24% cell viability at the highest concentration tested. These findings highlight the potential of this drug-free composite hydrogel as an efficient and biocompatible anticancer material, encouraging further in vivo and clinical studies to validate its therapeutic applications.

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This study systematically investigates the multifunctional performance of chitosan (CS) nanocomposites reinforced with zirconia nanoparticles (ZrO₂NPs), focusing on enhancements across structural, thermal, mechanical, optical, and dielectric properties. XRD-confirmed crystallinity reduction shows ZrO₂ NPs disrupt CS's semi-crystalline structure by breaking hydrogen-bonded networks, while introducing a dominant tetragonal phase with minor monoclinic contributions (< 5%). Thermogravimetric analysis (TGA) reveals a 100 °C increase in thermal stability (onset decomposition at 300 °C) and doubled residual mass (35% at 800 °C) for 15 wt.% ZrO₂/CS, attributed to nanoparticle-induced char reinforcement. Mechanical testing demonstrates a 330% increase in tensile strength (30 up to 130 MPa) and improved ductility (2.5% up to 4.2% strain) at 5 wt.% loading—outperforming TiO₂-reinforced CS. Optically, tunable bandgap narrowing (5.4–2.9 eV) enables UV shielding (20% transmittance at 15 wt.%) while preserving visible-light transparency. Dielectric analysis via the Havriliak-Negami (HN) framework reveals composition-dependent behavior: maximum dielectric constant (ε′ ≈ 280 at 360 K) occurs at 15 wt.% due to enhanced Maxwell–Wagner-Sillars polarization, while 20 wt.% loading causes agglomeration-induced saturation of dielectric loss. AC conductivity follows the universal power law, increasing with frequency/temperature. Crucially, DC conductivity peaks at 10 wt.% (5.1 × 10⁻⁷ S/m at 320 K), indicating optimal percolative network formation, then plummets to 8.0 × 10⁻⁸ S/m at 20 wt.% due to agglomeration-disrupted pathways. The reduction in activation energy (from 0.41 to 0.26 eV) confirms enhanced charge mobility, although microstructural limitations become dominant beyond 10 wt.%. These synergistic improvements—arising from ZrO₂’s interfacial interactions, quantum confinement, and structural reinforcement—underscore the nanocomposites’ promise for biomedical scaffolds, UV-protective coatings, and flexible electronic applications.

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The wettability and evaporation dynamics of polymeric surfaces are pivotal for optimizing their performance in applications such as coatings, microfluidics, and biomedical devices. This study examines the drying behavior of water and colloidal droplets on polystyrene (PS), polymethyl methacrylate (PMMA), and polydimethylsiloxane (PDMS) substrates, benchmarked against glass, to elucidate the effects of surface roughness and wettability. Employing a phenomenological concept, the time-dependent Ginzburg–Landau (TDGL) equation with a ratchet potential, we model the interplay between surface topography and fluid dynamics, capturing evaporation patterns and particle deposition. Surface modifications reveal that molecular level of roughness and hydrophobicity significantly influence droplet spreading and drying rates, with PS bead colloidal drying highlighting substrate-specific deposition morphologies. These insights enable the tailoring of polymeric surfaces for enhanced functionality, offering potential advancements in surface engineering and interfacial science.

In this study, the conditions favorable for enhanced stability of magnetite nanoparticles synthesized via the coprecipitation of iron salts were evaluated for enhancing their effectiveness in various applications and ensuring homogeneous nanoparticle dispersion over time. The impact of various factors such as sonication power and time, use of pH modifiers, and surface preparation on the temporal evolution of transmittance of nanofluids was investigated by analyzing the Euclidian distances of 350- and 650-nm spectra for each time. Nanofluids were prepared by dispersing magnetite nanoparticles in deionized water using an ultrasonic homogenizer in line with the factorial experimental design that generated 32 runs. The stability of nanofluid was evaluated via direct observation, visible spectroscopy, and Zeta potential measurement. Results indicated that the combination of unwashed nanoparticles, pH-modified nanoparticles using NaOH, and those sonicated at 400 W for 60 min enhanced the stability of nanofluids, resulting in a homogeneous and stable dispersion. These findings offer valuable insights into optimize the synthesis conditions of magnetite nanofluids with potential applications in fields such as magnetic hyperthermia and controlled drug delivery.

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