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Optical Properties and Model of the Electronic and Spatial Structure of Hypercrosslinked Polystyrene
摘要： A number of hypercrosslinked polystyrene networks are studied. The networks are obtained via additional crosslinking of granules of styrene copolymer with 0.5% divinylbenzene (0.3–0.5 mm) and micro-granules with 1% divinylbenzene (3.5 μm) using monochlorodimethyl ether to densities of crosslinking from 60 to 500%. It is found that as the degree of crosslinking grows, the absorption in the electronic spectrum of the polymer extends to the visible region, and the granules change color (toward as dark as black); this phenomenon is much less expressed for microgranules and milled materials. For a consistent explanation of these two observations, assumptions are made about the appearance and increase in the contrast of density fluctuations of a tracery hypercrosslinked network and light scattering on such micro-inhomogeneities in the volume of particles of the compared series of polymers.
关键词： hypercrosslinked polystyrene,network structure,electronic spectra,degree of crosslinking
更新于2025-09-19 17:15:36
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Polymeric fibers and microporous films by photo-crosslinking of triphenylene-derived liquid crystals
摘要： Two series of photoreactive discotic liquid crystals consisting of a triphenylene core and six cinnamate units with one (TPC1n) or two (TPC2n) n-alkoxy groups (CnH2n+1O; n = 10–14), respectively, as peripheral groups are synthesized. Both of them are polymerized into ?bers up to 2 mm long by UV irradiation in liquid paraf?n in the columnar LC temperature ranges. The ?ber structures seem to be preconstructed in liquid paraf?n. In addition, TPC2n are shown to form microporous ?lms up to 15 μm in diameter by simply casting the solutions of some solvents followed by drying for several minutes in air at room temperature. Photoirradiation of the ?lms in the LC temperature range converts them to polymeric ones while preserving the microporous and hexagonally ordered structure. From comparison with TPC1n and the hydrogenated derivative of TPC212, the porous ?lm-forming property is suggested to result from the combination of the double bond of the cinnamoyl group and the two long alkoxy chains on the phenyl ring.
关键词： microporous ?lm,cinnamate,self-assembly,photo-crosslinking,structure-property relations,photopolymerization,triphenylene-derived liquid crystals,?ber,membranes
更新于2025-09-19 17:15:36
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Thermally-stable low-loss polymer dielectrics enabled by attaching crosslinkable antioxidant to polypropylene
摘要： Polymer dielectrics with low loss and high-temperature tolerance are extremely desirable as electrical energy storage materials for advanced electronics and electrical power applications. They can allow fast switching rates during power conversion and therefore achieve high power densities without thermal issues. Here we explore polypropylene (PP), the state of the art dielectric polymer, and present an innovative approach to substantially improve the thermal stability and concurrently reduce the dielectric loss of PP. In particular, crosslinkable antioxidant groups, hindered phenol (HP), are incorporated into PP via well-controlled chemical synthesis. The grafted HP can simultaneously serve as radical scavenger and crosslinker, thereby constraining thermally decomposed radicals and charge transport in the synthesized PP-HP copolymer. As a result, the upper-temperature limit of PP-HP is greatly extended to 190 ?C and the electrical loss is even gradually reduced upon thermal annealing. The copolymer after heating under 190 ?C exhibits better dielectric properties than the PP without any thermal treatment. The experimental results indicate that the PP-HP copolymers are promising materials for high temperature, low loss, and high voltage dielectric applications.
关键词： energy storage,crosslinking,hindered phenol antioxidants,functionalized polypropylene,high-temperature low-loss dielectrics,electrical leakage current
更新于2025-09-19 17:13:59
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Novel Siloxane-Modified Epoxy Resins as Promising Encapsulant for LEDs
摘要： This study investigated a new category of transparent encapsulant materials for light-emitting diodes (LEDs). It comprised a phenyl group that contained siloxane-modified epoxy (SEP-Ph) hybridized with a cyclic tetrafunctional siloxane-modified epoxy (SEP-D4) with methylhexahydrophthalic anhydride (MHHPA) as a curing agent. The SEP-Ph/SEP-D4 = 0.5/0.5 (sample 3) and SEP-D4 (sample 4) could provide notably high optical transmittance (over 90% in the visible region), high-temperature discoloration resistance, low stress, and more crucially, noteworthy sulfurization resistance. The lumen flux retention of the SEP encapsulated surface mounted device LEDs remained between approximately 97% and 99% after a sulfurization test for 240 h. The obtained comprehensive optical, mechanical, and sulfurization resistance proved the validity and uniqueness of the present design concept with complementary physical and chemical characteristics.
关键词： crosslinking density,surface mounted device LEDs,encapsulant,sulfurization resistance,siloxane-modified epoxy
更新于2025-09-16 10:30:52
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Newly developed thermoplastic polyolefin encapsulant–A potential candidate for crystalline silicon photovoltaic modules encapsulation
摘要： Thermoplastic polyolefin (TPO) is a newly developed non-crosslinking material for photovoltaic (PV) module lamination as an alternative to ethylene–vinyl-acetate (EVA) encapsulant. This article assesses its applicability as an encapsulant material. We report the results of various characterization tests for discoloration, optical, and thermal properties degradation before and after the UV accelerated test. To evaluate its weathering stability, the UV-365 acceleration test has been conducted on the glass to glass TPO laminate, with EVA as a benchmark. In 50 days of weatherability tests, the transmittance of EVA significantly reduced while TPO remained almost unchanged. The discoloration of TPO is around nine times slower than that of EVA. The analytical tools like Raman spectroscopy, fluorescent imaging, and spectra have been used to assess the degradation behavior, which indicates a clear difference between EVA and TPO based encapsulant. Thermal properties (glass and melt transitions) of TPO and EVA have been studied through heat-cool-heat cycle testing by differential scanning calorimeter (DSC). This test confirmed that TPO thermal properties remain almost unchanged, whereas EVA shows significant changes after 50 days of UV exposure. In the thermogravimetry analysis (TGA) results, we found that TPO is stable till a significantly higher temperature than EVA. Additionally, the 180° peel adhesion test suggests that TPO has a higher adhesion strength than EVA. This work will help in understanding the applicability of newly developed non-crosslinking TPO as a potential replacement for EVA for the PV modules.
关键词： Thermoplastic polyolefin,Photovoltaic module,Encapsulant,Non-crosslinking,Ethylene-vinyl-acetate
更新于2025-09-16 10:30:52
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In Situ Light-Initiated Ligands Crosslinking Enables Efficient All-Solution-Processed Perovskite Light-Emitting Diodes
摘要： Solution process has been considered to be an effective method to fabricate emitting layer (EML) in light-emitting diodes (LEDs). However, the fabrication of charge transport layer (CTL) above the perovskite EML by solution processing is challenging. Herein, we incorporated polymerizable molecules, conjugated linoleic acid (CLA), as surface ligands to passivate perovskite QDs. The polymerized CLA can create a crosslinked QD film, which allows the solution deposition of subsequent CTLs. The theoretical calculations reveal that the binding energy of polymerized CLA with QDs increased, and the strong ligands binding state can better passivate the surface and improve the stability of QDs. As a result, all-solution-processed multilayer perovskite LEDs were fabricated with performance of a max luminance of 2470 cd/m2 for CsPbBr3-based devices, and a peak EQE of 2.67% for CsPbI3-based devices. These results demonstrate that the in situ light-initiated ligands crosslinking can be an effective strategy in all-solution-processed optoelectronic devices.
关键词： optoelectronic devices,light-emitting diodes,solution processing,perovskite quantum dots,ligands crosslinking
更新于2025-09-16 10:30:52
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Interfacial crosslinked controlled thickness graphene oxide thin-films through dip-assisted layer-by-layer assembly means
摘要： The augmentation of research in graphene based thin films has been of great interest to various current industrial stakeholders. This is mainly due to the wide scope of films applications, ranging from nanoelectronics to separation membranes. Therefore, establishing a relation between graphene based thin film key characteristics and the fabrication operating conditions is of high significance. This study entails the successful fabrication of controlled-thickness crosslinked graphene oxide (GO) thin films on inexpensive silicon-based glass slide substrates. The method of film fabrication used is the dip-assisted layer-by-layer assembly, which has an added advantage of step-control of thin film thickness, good film uniformity and continuity. The thickness was primarily tuned through the use different sized crosslinkers; a covalent based sub-nanometer sized p-phenylenediamine and an electrostatic based polyethyleneimine on an interchangeable assembly with GO. Pre film fabrication, Fourier Transform Infra-Red and X-Ray Photoelectron Spectroscopy characterizations were carried out to determine the nature of interactions between GO and the crosslinkers. Post film fabrication, scanning electron microscopy, water contact angle measurements and profilometry analysis were undertaken for film continuity, hydrophilicity and thickness measurements respectively. A strong linear trend between film thickness of the differently crosslinked films and the number of bi-layers was established.
关键词： Graphene oxide,Thin film,Crosslinking,Thickness,Layer-by-layer
更新于2025-09-12 10:27:22
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Crosslinkable Bis(diphenylamine)‐Substituted Mixed Dihydroindeno[1,2‐b]fluorenes for Solution‐Processed, Multilayer OLEDs
摘要： The synthesis and application of a series of crosslinkable bis(diphenylamine)-substituted mixed dihydroindeno[1,2-b]fluorenes as model systems for the fabrication of solution-processed, multilayer OLEDs is described. Introducing a novel functionalization approach by C(sp3)-C(sp2) Suzuki-Miyaura reactions, the synthesis is based on a modular strategy, leading to eight nearly isoelectronic derivatives which allow for the observation of structure-property-relationships in the context of crosslinkable hole-transport materials, e.g. for use in organic light-emitting diodes (OLEDs). By systematically altering structural parameters, such as the number of crosslinkable oxetane moieties per molecule (2-6 moieties) and their position of attachment (geminal and/or lateral), process relevant thermal properties such as thermal stability and glass-transition temperature can be influenced and allow for the investigation of their impact on the crosslinking behavior and the resulting device performance.
关键词： polymerization,materials science,crosslinking,oxetane,OLED
更新于2025-09-11 14:15:04
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Interfacial Modification and Defect Passivation by Crosslinking Interlayer for Efficient and Stable CuSCN-Based Perovskite Solar Cell
摘要： Study of the inorganic hole-transport layer (HTL) in perovskite solar cell (PSC) is gathering attention due to the drawback of conventional PSC design, where the organic HTL with salt dopants majorly participates in the degradation mechanisms. On the other hand, inorganic HTL secures better stability, while it offers difficulties in the deposition and interfacial control to realize high-performing devices. In this study, we demonstrate polydimethylsiloxane (PDMS) as an ideal polymeric interlayer which prevents the interfacial degradation, and improves both photovoltaic performance and stability of CuSCN-based PSC by its crosslinking behavior. Surprisingly, the PDMS polymers are identified to form chemical bonds with perovskite and CuSCN, as shown by Raman spectroscopy. This novel crosslinking interlayer of PDMS enhances the hole-transporting property at the interface and passivates the interfacial defects, realizing the PSC with high power-conversion efficiency over 19%. Furthermore, the utilization of PDMS interlayer greatly improves the stability of solar cells against both humidity and heat, by mitigating the interfacial defects and interdiffusion. The PDMS-interlayered PSCs retained over 90% of the initial efficiencies, both after 1000 h under ambient condition (unencapsulated) and after 500 h under 85°C/85% relative humidity (encapsulated).
关键词： Crosslinking Interlayer,Inorganic Hole-Transport Layer,Defect Passivation,Stability,Perovskite Solar Cell
更新于2025-09-11 14:15:04
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Corneal stromal demarcation line after 4 protocols of corneal crosslinking in keratoconus determined with anterior segment optical coherence tomography
摘要： We read with great interest the recent publication by Spadea et al. about the depth of corneal stromal demarcation lines after the following 4 corneal crosslinking (CXL) protocols: epi-off Dresden (C-CXL), epi-off accelerated (TE-CXL), enhancers-assisted transepithelial (A-CXL), and iontophoresis-assisted CXL (I-CXL). The authors conclude that the difference in CXL efficiency estimated by the demarcation line would only be secondary to the stromal penetration of riboflavin and ultraviolet-A light. They suggest that because I-CXL had better stromal penetration, it would also have greater CXL efficacy.
关键词： anterior segment optical coherence tomography,Corneal stromal demarcation line,keratoconus,corneal crosslinking
更新于2025-09-10 09:29:36