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Effect of Molecular Weight of Polyethylene Glycol on the Sheet-thickness and Photocatalytic Performance of MoS2 Nanoparticles
摘要： Molybdenum disulfide (MoS2) nanomaterials have attracted considerable attention recently owing to its unique photoelectrochemistry property and promising applications in the conversion of solar energy to chemical energy and environmental purification. Flower-like MoS2 photocatalyst was synthesised via hydrothermal method in this work. To achieve the MoS2 nanoparticles with various sheet-thickness, polyethylene glycols (PEG) with deferent molecular mass were employed as additives in the preparation process. The effects of the molecular weight of PEG on the micro structure and crystal structure of MoS2 nanoparticles were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscope (HRTEM) and X-ray diffraction (XRD). The photocatalytic properties of as-synthesized products were evaluated by the degradation of methylene blue (MB) under ultraviolet irradiation. The results suggest that the molecular weight of PEG could affect the sheet thickness of the MoS2 particles. In addition, the degradation rate of MB show that the photocatalytic performance of MoS2 nanoparticles is closely related to their sheet thickness, the photocatalytic activity reduced with the decrease of sheet thickness of MoS2 nanoparticles which is mainly attributed to the reduction of the active sites.
关键词： Photocatalytic performance,MoS2 nanoparticles,Hydrothermal method,PEG,molecular weight,Sheet-thickness
更新于2025-09-23 15:21:01
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Impact of refractive index increment on the determination of molecular weight of hyaluronic acid by muti-angle laser light-scattering technique
摘要： Hyaluronic acid (HA) is applied in a number of medical applications and HA of different molecular weight (Mw) are used in different pharmaceutical preparations. In determination of Mw by muti-angle laser light-scattering (MALS), refractive index increment (dn/dc) is an important parameter for accuracy. Herein, the influence of dn/dc on the Mw of HA in stroke-physiological saline solution is investigated by MALS in this work. Additionally, the Mw variation of HA in the manufacturing process of preparations is measured. It is shown that each HA sample corresponds to a specific value of dn/dc, which is varied from 1.38 to 1.74 L/g with the Mw increasing from 13.5 to 2840 kDa in solution. It is indicated by the results from both MALS approach and viscometry that appropriate dn/dc should be selected for Mw determination. In steam sterilization process of preparations at 121 °C, the Mw and conformation of HA can be accurately and rapidly determined by MALS. This work provides a precise method to determine the Mw of HA in the medical applications and preparation industries.
关键词： Molecular weight,Viscometry,Muti-angle laser light-scattering,Steam sterilization,Hyaluronic acid,Refractive index increment
更新于2025-09-23 15:19:57
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Rewritable Optical Patterns in Light Responsive Ultra High Molecular Weight Polyethylene
摘要： Spiropyran is used as a photochromic dye to create colored patterns in highly drawn ultra high molecular weight polyethylene (UHMW PE) films. The dye is incorporated in highly crystalline, drawn UHMW PE tapes and fibers and isomerizes to its merocyanine state upon UV light irradiation, resulting in a color change from transparent to purple. The isomerization from merocyanine to spiropyran to erase the color can be simply induced using heat or a green LED light. The combination of the use of a mask and the reversibility of the isomerization results in colored patterns which can be written, erased and re-written using UV light and heat or green LED light.
关键词： Polymer fibers,ultra high molecular weight polyethylene,photochromism,light responsive materials,rewritable optical materials,spiropyran
更新于2025-09-19 17:15:36
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Controlled synthesis of unsubstituted high molecular weight poly( <i>para</i> -phenylene) <i>via</i> Suzuki polycondensation-thermal aromatization methodology
摘要： Suzuki polycondensation-thermal aromatization methodology was developed as a versatile new route to structurally regular, unsubstituted high molecular weight poly(para-phenylene) (PPP). The utility of this methodology was demonstrated by synthesizing PPP from both cis- and trans-precursor prepolymers 1a-b. The structure of precursor prepolymers containing exclusively 1,4-repeating units with the hydroxyphenyl group at the chain end was determined by two-dimensional NMR spectroscopy. Pyrolysis of trans-poly(para-phenylene) precursor 1b resulted in complete aromatization to PPP containing an average of 110 phenylene units in the polymer chain. The thermal conversion of precursor polymers to polyphenylene is a straightforward process leading to pristine PPP without significant chain degradation as confirmed by solid-state NMR and TGA analysis. The characterization of PPP by solid-state NMR, UV-vis absorption, fluorescence emission and IR spectroscopy, TGA, and conductivity measurements exhibits significant features for electronic and photoelectronic application, such as broadened absorption, high thermal stability, and typical conducting properties.
关键词： Suzuki polycondensation,NMR spectroscopy,high molecular weight,Poly(para-phenylene),thermal aromatization
更新于2025-09-19 17:13:59
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Tunnel oxide passivating electron contacts for high‐efficiency n‐type silicon solar cells with amorphous silicon passivating hole contacts
摘要： Organic photovoltaics (OPVs) consisting of a wide bandgap polymer donor and a nonfullerene acceptor (NFA) have received attention because they can effectively overcome the weaknesses of efficiency and stability for fullerene-based OPVs. One of the NFAs, ITIC, shows an excellent power conversion efficiency, as well as controllable solubility, absorption, crystallinity, and energy level. Thus, high-efficiency OPVs could be achieved by developing polymer donors appropriate for use with ITIC-based OPVs. In this study, the synthesized polymer donor, PBDTT-8ttTPD, containing alkylthieno[3,2-b]thiophene as π-bridge and thieno[3,4-c]pyrrole-4,6(5H)-dione (ttTPD) shows strong absorption with a sharp peak edge at around 700 nm. In addition, the high hole mobility and face-on oriented polymer structures in the blend films make ttTPD the best candidate for the donor in NFA-based OPVs. Notably, the molecular weight of the face-on preferred polymer donor is crucial for determining the power conversion efficiency (PCE) of the NFA-based devices. A high molecular weight improves the π?π stacking ordering, absorption, and nanomorphology of the blend films, resulting in a dramatic PCE improvement from 5.76% to 11.05% compared with that of the fullerene-based OPV device (7.86%).
关键词： organic photovoltaics,nonfullerene acceptors,molecular weight,TPD-based polymer,wide band gap donnor polymer
更新于2025-09-19 17:13:59
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Influence of polymer molecular weight on the properties of in situ synthesized silver–methylcellulose nanocomposite films with a CO2 laser
摘要： We investigate the in?uence of polymer molecular weight on the properties of silver–methylcellulose (Ag–MC) nanocomposite ?lms synthesized by the irradiation of a CO2 laser. Although the reduction power of MC with a smaller molecular weight turns out to be stronger than that with a larger molecular weight in the solution phase, we do not see such a clear difference when MC is in the matrix phase. For the 30 s irradiation at the laser power of 0.8 W, the size of Ag nanoparticles (NPs) in the two types of MC matrix is similar, and it is about 30 nm. However, for the longer irradiation time at the same laser power, aggregation of Ag NPs set in, and it is more serious for the Ag–MC ?lm with MC of larger molecular weight. We also carry out the antibacterial test with the Ag–MC ?lms, and ?nd that the Ag–MC ?lm synthesized at the lower laser power and shorter irradiation time generally exhibits a stronger antibacterial effect.
关键词： antibacterial effect,polymer molecular weight,CO2 laser,silver–methylcellulose nanocomposite
更新于2025-09-12 10:27:22
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Origin of the High Donor-Acceptor Composition Tolerance in Device Performance and Mechanical Robustness of All-Polymer Solar Cells
摘要： High tolerance regarding photovoltaic performance in terms of donor:acceptor (D:A) composition ratio is reported for all-polymer solar cells (all-PSCs), which is a crucial advantage in producing large-scale devices with high reproducibility. To understand the origin of high D:A ratio tolerance in all-PSCs, we investigate the molecular weight (MW) effects of the P(NDI2OD-T2) polymer acceptor (PA) on photovoltaic and mechanical robustness of PBDB-T:P(NDI2OD-T2) all-PSCs. Also, we compare the all-PSCs with other types of PSCs consisting of the same polymer donor but using small molecule acceptors (SMAs) including ITIC and PC71BM. It is observed that the D:A ratio tolerances of both the photovoltaic and mechanical properties are highly dependent on the PA MW and the acceptor material types. For example, at a high D:A ratio of 15:1, all-PSCs using high MW PA (number-average molecular weight (Mn)= 97 kg mol-1) exhibit 13 times higher normalized power conversion efficiency (PCE) than all-PSCs using low MW PA (Mn= 11 kg mol-1), and 20 times higher than ITIC-based PSCs. In addition, the electron mobilities in all-PSCs based on high MW PA are well maintained even at very high D:A ratio, whereas the electron mobilities in low MW PA all-PSCs and SMA-based PSCs decrease by 3- and 4-orders of magnitude, respectively, when the D:A ratio increases from 1:1 to 15:1. Thus, we suggest that the formation of tie molecules and chain entanglements by long polymer chains bridging adjacent crystalline domains is the main origin of excellent D:A tolerance in both mechanical robustness and photovoltaic performance. This work provides an important material design guideline for the reproducible production of flexible and stretchable all-PSCs.
关键词： molecular weight effects,mechanical robustness,donor-acceptor composition tolerance,photovoltaic performance,all-polymer solar cells
更新于2025-09-12 10:27:22
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A low molecular weight OLED material: 2-(4-((2-hydroxyethyl)(methyl)amino)benzylidene)malononitrile. Synthesis, crystal structure, thin film morphology, spectroscopic characterization and DFT calculations
摘要： 2-(4-((2-Hydroxyethyl)(methyl)amino)benzylidene)malononitrile (HEMABM) was synthesized from 4-[hydroxymethyl(methyl)amino]benzaldehyde and propanedinitrile to obtain a low molecular weight fluorescent material with an efficient solid-state emission and electroluminescence properties comparable to the well-known poly(2-methoxy-5(20-ethyl)hexoxyphenylenevinylene) (MEH-PPV). The HEMABM was used to prepare an organic light-emitting diode by a solution process. Despite the title compound being a small molecule, it showed optical properties and notable capacity to form a film with smooth morphology (10.81 nm) closer to that of polymer MEH-PPV (10.63 nm). The preparation of the device was by spin coating, the electrical properties such as threshold voltage were about 1.0 V for both HEMABM and MEH-PPV, and the luminance 1300 cd m?2 for HEMABM and 2600 cd m?2 for MEH-PPV. IR, NMR, and EI. Besides this low molecular weight compound was characterized by SCXRD, a quantitative analysis of the intermolecular interactions by PIXEL, density functional theory (DFT) calculations are reported.
关键词： electroluminescence,OLED,MEH-PPV,low molecular weight,solution process,HEMABM
更新于2025-09-11 14:15:04
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Effect of molecular weight of side chain liquid crystalline polymers on properties of liquid crystal physical gels
摘要： A series of side chain liquid crystalline polymers (SCLCPs) poly[ω-4′-cyano-(1, 1′-biphenyl)] acrylate (P0ACB) with di?erent molecular weight were prepared and used as gelator to fabricate liquid crystalline physical gels (LCPGs). The relationship between molecular weight of side chain liquid crystalline polymers and the properties of liquid crystalline physical gels were also discussed in detail. Testing results showed that when the molecular weight of polymers was less than 3.61 × 104, the minimum gelation concentration (MGC) of liquid crystalline physical gels decreased from 3 wt% to 0.2 wt% and gel-sol phase transition temperature (TGS) increased from 99 °C to 185 °C with increasing molecular weight. The driving voltage and contrast ratio increased obviously and the o? state response time decreased with increasing molecular weight. However, when the molecular weight of polymers was greater than 3.61 × 104, the stability and the electro-optical response properties of the liquid crystalline physical gels basically unchanged. The mechanical properties of liquid crystalline physical gels were a?ected signi?cantly by the molecular weight of polymers. The energy storage modulus of liquid crystalline physical gels increased from 1.6 × 103 Pa to 3.1 × 104 Pa with increasing molecular weight when the gelator concentration is 6.0 wt%.
关键词： Side chain liquid crystalline polymers,Liquid crystal physical gels,Molecular weight,Electro-optical response properties,Thermal stability
更新于2025-09-10 09:29:36
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The photo-stability of acrylic tri-block copolymer blends for the consolidation of cultural heritage
摘要： A variety of adhesives are used for the conservation of paintings. These materials include natural adhesives such as animal glues, waxes, and gums which may chemically degrade over time resulting in unwanted discoloration and mechanical failure. Synthetic adhesives have been introduced to address these concerns. However, most consolidating adhesives have not been specifically formulated and tested to meet the high demands of conservation, ultimately resulting in undesirable physical and mechanical properties. Additionally, some synthetic adhesives are less stable and may cross-link making it difficult to remove years after application. This paper investigates the photo-stability of commercially available tri-block acrylic copolymers (PMMA-PnBA-PMMA) to assess their potential long-term serviceability as consolidants for flaking paint. These copolymers were combined with synthetic low molecular weight resins to reduce viscosity of the adhesive and provide tack. The polymer blends underwent accelerated aging under simulated indoor conditions. Blends were analysed for degradation using Fourier-transform infrared spectroscopy and size exclusion chromatography. Upon irradiation, acrylic copolymers (PMMA-PnBA-PMMA) undergo shifts to higher and lower molecular weight, suggesting that degradation occurs by polymer cross-linking and chain scission. Furthermore, the acrylic copolymer degradation rate was influenced by the type of low molecular weight resin. However, with the addition of a hindered amine light stabilizer these blends exhibited minimal changes in molecular weight. Lastly, the peel strength of the blends were investigated and shown to have comparable peel strength to a popular commercial material, Paraloid? B-72, often used in consolidation thus showing their promise for use within cultural heritage.
关键词： Adhesion,Consolidating adhesive,T-peel strength,Acrylic copolymer,Low molecular weight resin,Painting,Photo-chemical stability,Hindered amine light stabilizer,Urea-aldehyde,Conservation,Hydrogenated hydrocarbon
更新于2025-09-09 09:28:46