Search Results (1,223)

Chromophore domains were proposed in a previous work as the mediators of self-healing of optical properties in dye-doped polymers. A statistical mechanical model based on domains matches all observed self-healing dynamics as a function of dye concentration, temperature and light intensity. This suggests that domains are responsible. However, there is no direct observation of domains, nor has their physical morphology been determined. This work reports the first observation of domains in a self-healing polymer using Resonant Soft X-ray Scattering (RSoXS), which gives a domain size in the range of 39.3 Å to 62.8 Å. This range includes the domain model’s prediction of an average domain size of roughly 30 molecules, which is about 56 Å, if the molecules form a loosely packed ball. X-ray scattering of samples of concentration spanning from neat polymer to the saturation limit of Disperse Orange 11 (DO11) dye in poly (methyl methacrylate) (PMMA) polymer shows domains in the expected size scales, with the mode of the effective scattering width varying little with concentration. However, for constant domain shape, the mode peak would decrease in q with increasing concentration, according to the domain model. This work suggests that the domain shape might change with concentration, which warrants further investigations of domain topology and geometry. The important evidence presented in this work is the direct experimental observation of domains, which is central to self-healing models. Full article

Work investigates the doping of molybdenum oxide (MoO_x) with tungsten (W). The successful incorporation of W into the MoO_x lattice was confirmed through X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS). Structural and optical analysis revealed the presence of oxygen vacancies within the W-MoO_x film, which are known to facilitate resistive switching (RS) in memristive devices. Based on this, a flexible memristor with the structure PET/ITO/W-MoO_x/polymethyl methacrylate (PMMA)/Al was fabricated. PMMA was strategically introduced between the W-MoO_x layer and the aluminum electrode to modulate interfacial properties that influence RS behavior. The W-MoO_x/PMMA-based memristor exhibited good resistive switching characteristics, with a memory window of approximately 12 and a retention time exceeding 2 × 10⁴ s, demonstrating a non-volatile memory behavior. In the high-resistance state (HRS), the conduction mechanism under higher applied voltages follows a space-charge-limited current (SCLC) model, indicating that the RS process is primarily governed by charge trapping and de-trapping at the interface. Overall, the consistent and robust switching performance of the W-MoO_x/PMMA heterostructure underlines its potential as a reliable functional layer for next-generation resistive random-access memory (ReRAM) devices. Full article

Acrylic solid surface composites made of poly (methyl methacrylate) (PMMA) and aluminum trihydrate, Al(OH)₃ (ATH) are widely used in furniture and interior applications. However, independent brand comparative data, especially on density-normalized (“specific”) properties, remain limited. This study quantifies the flexural response of 11 commercial sheets (6, 8, and 12 mm, including one translucent) under ISO 178 three-point bending and evaluates the effects of heating and cooling relevant to thermoforming. The density is concentrated in the range 1680–1748 kg/m³ (weighted mean of 1712 kg/m³). The flexural strength ranged between 51 and 79 MPa, divided into three groups—high (76–79 MPa), medium (63–67 MPa), and low (51–56 MPa) levels, while the modulus ranged between 7700 and 9400 MPa with a narrow dispersion. The strength showed no significant correlation with density, while the modulus increased with density, indicating that stiffness is composition-dominated, while strength is influenced by factors related to microstructural defects/particle boundaries. Heating at 160 °C and subsequent cooling have a significant influence on flexural strength and strain. Flexural strength increased by an average of approximately 7%, and flexural strain increased by approximately 12%, while the modulus remained virtually unchanged (within ±0.5%); additionally, shock cooling did not bring any benefits. The density-normalized parameters (σ/ρ, E/ρ) reflected these trends, allowing for a more accurate comparison when limited by mass or deformation. Overall, the results are broadly consistent with manufacturers’ declarations and demonstrate that thermoforming-relevant heating at 160 °C, followed by cooling, can be used not only to improve formability but also to modestly increase flexural strength and strain without compromising stiffness. Full article

Salisbury screen-type radar absorption structures (RASs) consisting of a resistance sheet, a spacer, and a conductive base provide an efficient method for microwave absorption. An impedance-matched resistance sheet allows microwaves to enter, whereas superior microwave absorbers enhance their performance further. In the present work, an impedance matching composite film was prepared by using polymer/iron/iron nanowires. By varying the polymer, poly (methyl methacrylate) (PMMA), poly (vinylidene fluoride) (PVDF), and poly (vinyl alcohol) (PVA), to iron powder ratios (1:1, 2:1, and 4:1), composite films were synthesized and examined by scanning electron microscopy, X-ray diffraction, and the four-point probe method to determine the materials’ characteristics. An impedance-matched composite film was prepared based on the selected composition with 1–10 wt.% iron nanowire additions. Experimental results showed that the polymeric composite film prepared by a ratio of iron-PVA of 4:1 exhibited a sheet resistance of 49 ± 9.7 Ω/sq due to well dispersion of iron powder in PVA. With 1 wt.% Fe nanowire addition, the optimal composite sheet resistance was 329.7 ± 45.3 Ω/sq, which corresponded to an impedance matching degree (i.e., |Z_in/Z₀| value) of 0.88 ± 0.12 and can be used as a resistance sheet for a Salisbury screen-type absorber in RAS applications. Full article

Cell population and vascular vessel distribution analysis in membrane-based scaffolds for tissue engineering is crucial. Biomimetic nanostructured membranes of methyl methacrylate/hydroxyethyl methacrylate and methyl acrylate/hydroxyethyl acrylate (MMA)1-co-(HEMA)1/(MA)3-co-(HEA)2 loaded with 5% wt SiO2-nanoparticles (Si-M) were doped with zinc (Zn-M) or doxycycline (Dox-M). Critical bone defects were effectuated on six New Zealand-bred rabbit skulls and then they were covered with the membrane-based scaffolds. After six weeks, bone cell population in terms of osteoblasts, osteoclasts, osteocytes, fibroblasts, and M1 and M2 macrophages and vasculature was determined. The areas of interest were the space above (over) and below (under) the membrane, apart from the interior (inner) compartment. All membranes showed that vasculature and most cell types were more abundant under the membrane than in the inner or above regions. Quantitatively, osteoblast density increased by approximately 35% in Zn-M and 25% in Si-M compared with Dox-M. Osteoclast counts decreased by about 78% in Dox-M, indicating strong inhibition of bone resorption. Vascular structures were nearly twofold more frequent under the membranes, particularly in Si-M, while fibroblast presence remained moderate and evenly distributed. The M1/M2 macrophage ratio was higher in Zn-M, reflecting a transient pro-inflammatory state, whereas Dox-M favored an anti-inflammatory, pro-regenerative profile. These results indicate that the biomimetic electrospun membranes functioned as architectural templates that provided favorable microenvironments for cell colonization, angiogenesis, and early bone regeneration in a preclinical in vivo model. Zn-M membranes appear suitable for early osteogenic stimulation, while Dox-M membranes may be advantageous in clinical contexts requiring modulation of inflammation and osteoclastic activity. Full article

Objective: The aim of this study was to evaluate surface roughness (R_a) and microbial adhesion on four provisional prosthodontic materials in comparison to zirconium oxide. Methods: Four provisional prosthodontic restorative materials were evaluated in this study: poly methyl methacrylate (PMMA) acrylic resin (ALIKE; GC America Inc., Alsip, IL, USA), dimethacrylate (Bis-acryl) resin (Integrity; Dentsply Sirona, Charlotte, NC, USA), 3D-printed temporary crown and bridge resin (Formlabs Inc., Somerville, MA, USA), prepolymerized poly methyl methacrylate (milled PMMA) (Harvest Dental Laboratory Products, Brea, CA, USA), and zirconium oxide (Ivoclar Vivadent AG, Liechtenstein, Germany). A total of 90 samples were prepared and divided into two groups per material (treated and untreated). Provisional material samples were prepared per manufacturer’s instructions, polished with the same sequence using acrylic burs followed by Acrylipro silicone polishers (Brasseler, Savannah, GA, USA), and pumice with a goat brush. Zirconia was polished with a green grinding stone (ZR Grinders; Brassseler, Savannah, GA, USA), followed by a feather lite (Dialite ZR polisher; Brasseler, Savannah, GA, USA). The Ra of all samples was measured using a digital profilometer. Sterilized samples were incubated in Todd Hewitt yeast extract (THY) broth containing Candida albicans SC5314 and Streptococcus mutans BM71 at 37 °C under anaerobic conditions for 72 h. Subsequently, the number of colony-forming units (CFU) adhered to each sample was determined by serial dilution plating. Normality and homoscedasticity were assessed prior to statistical analysis. Welch’s ANOVA was then performed to evaluate differences among all samples, followed by Games–Howell post hoc tests for pairwise comparisons. A p < 0.05 was considered significant in all experiments. Results: Zirconia demonstrated the lowest surface roughness and significantly reduced adhesion of S. mutans and C. albicans compared to all other materials (p < 0.001). Milled PMMA exhibited significantly lower roughness and microbial adhesion than conventional PMMA (p < 0.001), with no significant difference from Printed PMMA in microbial adhesion. Additional pairwise differences were observed between Bis-acryl and PMMA (p = 0.0425), Milled and Printed PMMA (p < 0.0001), and Bis-acryl and Printed PMMA (p < 0.0001). Conclusions: Zirconia and milled PMMA showed superior surface properties and reduced microbial adhesion, supporting their use in long-term provisional restorations. Materials with higher microbial retention, such as self-curing PMMA, bis-acryl, and 3D-printed resins, may be less suitable for extended use. These findings guide material selection to improve clinical outcomes and highlight the need for further in vivo research. Full article

Carbon-based materials have emerged as promising biomaterials due to their biocompatibility and inherent antibacterial properties. Carbyne, a unique allotrope of carbon, characterized by sp-hybridized carbons forming alternating single and triple bonds, exhibits exceptional toughness. Herein, we explore the potential of carbyne-enriched plasma coatings for antibacterial applications in conjunction with micro- and nano-textured polymeric surfaces. We investigate and characterize carbyne-enriched plasma coatings onto superhydrophilic or superhydrophobic poly (methyl methacrylate) (PMMA) plasma micro-nanotextured surfaces. Our analysis evaluates the wetting properties and durability of these surfaces, particularly in liquid immersion conditions. The integration of carbyne-enriched plasma coatings serves a dual purpose: it enhances the chemical bactericidal action and protects surface micro-nanostructures from deformation due to capillary forces thanks to the material’s innate toughness. The results show that the micro-nanotextured and carbyne-enriched coated PMMA surfaces exhibit a significant bactericidal activity as expressed by a bactericidal index of approximately 50%, owing to the combined effect of both the surface topography and the plasma-deposited carbyne coating. Full article

The traditional chemical vapor deposition (CVD)graphene transfer process generates a large amount of solvent waste, posing a significant sustainability challenge. To address this, we designed a Cyclic Cleaning Multi-Chamber (CCMC) system. Inspired by Soxhlet extraction, the CCMC enables closed-loop solvent recycling through integrated distillation, condensation, and reflux mechanisms. Experimental results show that the system effectively removes poly(methyl methacrylate) (PMMA) residues from transferred graphene without damaging its structural integrity, a finding confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The CCMC system achieves a solvent recovery efficiency of over 98% across 25 cycles using acetone, significantly reducing solvent consumption compared to conventional methods. While providing this substantial environmental benefit, the energy demand remains moderate, increasing by only about 15 kWh. These results position the CCMC as a scalable, eco-friendly solution for the semiconductor and nanomaterial industries, promoting the broader adoption of sustainable manufacturing practices. Full article

The growing demand for sustainable solutions in the plastics industry has highlighted the need to reintroduce post-industrial polymer waste into high-performance applications. This study focuses on the mechanical recycling of automotive scraps containing variable proportions of polycarbonate (PC), acrylonitrile–butadiene–styrene (ABS), and a commercial PC/ABS blend. After determining the composition of two representative batches, a screening of seven commercial compatibilizers and impact modifiers was performed to improve impact strength. Among them, an ethylene–methyl acrylate–glycidyl methacrylate (E-MA-GMA) terpolymer was identified as the most effective additive. Its influence was further investigated through a mixture design approach, varying the composition of the three polymer phases and the additive content (0–10 wt.%). The resulting response surface model revealed a significant increase in impact resistance in PC-rich formulations with increasing E-MA-GMA content, while ABS and PC/ABS showed more complex trends. Rheological, mechanical, and thermal analyses supported the observed behavior, suggesting improved matrix compatibility and reduced degradation during processing. The proposed model enables the prediction of impact performance across a wide range of compositions, offering a practical tool for the optimization of recycled blends. These findings support the potential of targeted compatibilization strategies for closed-loop recycling in the automotive sector. Full article

Directed self-assembly (DSA) of polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) has garnered substantial interest for semiconductor manufacturing, particularly for fabricating contact holes and vias. However, its application is limited by the low etch selectivity between the PS and PMMA domains. Here, we report an acid-responsive block copolymer, PS-N=CH-PMMA, incorporating a Schiff base (-N=CH-) linkage between the two blocks to impart acid sensitivity. The copolymer is synthesized via aldehyde-terminated PMMA (PMMA-CHO) precursors and is fully compatible with conventional thermal annealing workflows used for PS-b-PMMA. Uniform thin films with vertically oriented cylindrical domains were obtained, which could be directly converted into high-fidelity PS masks through acetic acid immersion without UV exposure. Graphoepitaxial DSA in 193i pre-patterned templates produced shrink-hole patterns with reduced critical dimension (CD) and improved local CD uniformity (LCDU). The shrink-hole CD was tunable by varying PMMA-CHO molecular weights. XPS confirmed selective cleavage of Schiff base linkages at the PS/PMMA interface under acidic conditions, while Ohta–Kawasaki simulations indicated interfacial wetting asymmetry governs etch fidelity and residual layer formation. Pattern transfer into TEOS layers was achieved with minimal CD loss. Overall, the acid-cleavable BCP enables scalable, high-fidelity nanopatterning with improved etch contrast, tunable process windows, and seamless integration into existing PS-b-PMMA lithography platforms. Full article

Methacrylate photopolymer resin (MPR) is widely used in various fields, including the biomedical field. There are several problems associated with their use: the potential toxicity of monomer residues during incomplete polymerization and the possibility of bacterial expansion. Doping polymers with nanoparticles is one of the ways to increase the degree of polymerization (protection from toxicity), improve the performance characteristics of the polymer, and add antibacterial properties. We used an in situ polymerization method to obtain the composites of MPR with tellurium nanoparticles (TeNPs) with a dopant concentration of 0.001, 0.01, or 0.1% (v/v). The composite of MPR+TeNPs had a higher degree of polymerization compared to MPR without NPs, improved mechanical properties, and pronounced antibacterial activity. The effects depended on the concentration of TeNPs. All of the studied composites had no cytotoxic effect on human cells. MPR+TeNPs 0.1% had the maximum antibacterial effect, which is probably realized through Te-dependent induction of oxidative stress (increase in the generation of 9-oxoguanine and long-lived reactive forms of proteins). The results obtained deepen the knowledge about the influence of NPs of leading metals on photopolymerization and the final properties of the methacrylate matrix, and the synthesized MPR+TeNP composites may find potential biomedical applications in the future. Full article

In this study, NiO nanoparticle–reinforced PMMA nanocomposites were fabricated by melt blending, and the influence of extrusion mixing time on structural and thermal properties was examined. Mixing durations of 6 and 12 min were applied, and the materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). These analyses confirmed the presence of NiO within the PMMA matrix and indicated that prolonged mixing promoted particle agglomeration. Thermal behavior was assessed by thermogravimetric analysis (TGA) at heating rates of 5, 10, 15, and 20 K·min⁻¹, and activation energies of decomposition were calculated using the Kissinger, Takhor, and Augis–Bennett methods. The results showed that extended mixing reduced composite homogeneity and adversely affected thermal stability. Incorporation of NiO nanoparticles decreased both the onset decomposition temperature and the activation energy compared to pure PMMA, facilitating earlier degradation. At 620 K, pure PMMA exhibited ~8% mass loss, whereas the 12 min blend showed ~12% loss. These findings highlight the importance of nanoparticle dispersion and processing parameters in governing the degradation behavior of PMMA/NiO nanocomposites. Full article

This study examines the chemical recycling of polymethylmethacrylate (PMMA) dental waste in semi-batch fixed-bed reactors via pyrolysis, aiming to convert this waste into the valuable monomer methyl methacrylate (MMA). First, the effect of temperature is analyzed in a laboratory-scale (30 g) semi-batch reactor at 350, 400 and 450 °C. In order to visualize the combined effect of temperature and increase in bed volume, experiments conducted at 350 °C in the laboratory (30 g) and on a pilot scale (20 kg) are compared. Experiments conducted at 475°C on technical and pilot scales are also compared to elucidate this behavior. A detailed process analysis is presented, considering different experiments conducted in a semi-batch technical-scale reactor. Experiments were conducted in a 2 L reactor at temperatures of 425 °C, 450 °C and 475 °C to understand the effects of heating rate and temperature on product yield and composition. The results show that at 425 °C, MMA was the primary liquid component, with minimal by-products, suggesting that lower temperatures enhance monomer recovery. Higher temperatures, however, increased gas yields and reduced MMA yield due to intensified thermal cracking. This study also highlights that char formation and non-condensable gases increase with the reactor scale, indicating that heat transfer limitations can influence MMA purity and yield. These findings emphasize that for effective MMA recovery, lower temperatures and controlled heating rates are optimal, especially in larger reactors where heat transfer issues are more prominent. This research study contributes to scaling up PMMA recycling processes, supporting industrial applications to achieve efficient monomer recovery from waste. Full article

This work presents the HX-responsiveness of the following heteroleptic donor–M–acceptor dithiolene complexes: Bu4N[MII(L1)(L2)] [M = Ni(1), Pd(2), Pt(3)], where L1 is the chiral acceptor ligand [(R)-α-MBAdto = chiral (R)-(+)α-methylbenzyldithio-oxamidate] and L2 is the donor ligand (tdas = 1,2,5-thiadiazole-3,4-dithiolato). Addition of hydrohalic acids induces a strong bathochromic shift and visible color change, which is fully reversed by ammonia (NH₃). Moreover, the sensing capability of 1 was further evaluated by deposition on a cellulose substrate. Exposure to HCl vapors induces an evident color change from purple to green, whereas successive exposure to NH₃ vapors fully restores the purple color. Remarkably, cellulose films of 1 were revealed to be excellent optical sensors against the response to triethylamine, which is a toxic volatile amine. Moreover, the HCl-responsiveness of the nonlinear optical properties of complexes 1, 2, and 3 embedded into a poly(methyl methacrylate) poled matrix was demonstrated. Reversible chemical second harmonic generation (SHG) switching is achieved by exposing the poled films to HCl vapors and then to NH₃ vapors. The SHG response ratio HCl–adduct/complex is significant (around 1.5). Remarkably, the coefficients of the susceptibility tensor for the HCl–adduct films are always larger than those of the respective free-complex films. Density Functional Theory (DFT) and time-dependent DFT calculations help in highlighting the structure–properties relationship. Full article

This study reports the development of electrospun poly(methyl methacrylate) (PMMA) fiber mats incorporating ibuprofen (IBU)-intercalated layered double hydroxides (LDH) for enhanced transdermal drug delivery systems (TDDS). IBU, in its anionic form, was successfully intercalated into LDH, which possesses anion exchange capabilities, and subsequently embedded into PMMA fibers via electrospinning. In vitro drug release experiments demonstrated that UPMMA–LDH–IBU fibers exhibited significantly higher IBU release than PMMA–IBU controls. This enhancement was attributed to the improved hydrophilicity and water absorption imparted by the LDH, as confirmed by contact angle and water uptake measurements. Furthermore, artificial skin permeation tests revealed that the UPMMA–LDH–IBU fibers maintained comparable release rates to those observed during buffer immersion, indicating that the rate-limiting step was the diffusion of IBU within the fiber matrix rather than the interface with the skin or buffer. These findings highlight the critical role of LDH in modulating drug release behavior and suggest that UPMMA–LDH–IBU electrospun fiber mats offer a promising and efficient platform for advanced TDDS applications. Full article