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Preparation and electromagnetic attenuation properties of MoS2–PANI composites: a promising broadband absorbing material
摘要： As an ideal electromagnetic (EM) wave absorber, it is prone to possess lightweight, thin matching thickness, broad absorption bandwidth and strong absorption performance. In this work, MoS2–PANI composites were prepared by situ chemical oxidative polymerization method, and the crystal structure, morphology, composition and EM properties were characterized. The microwave absorption properties of MoS2–PANI composites could be tuned by changing the PANI content to reach the best impedance match. The minimum reflection loss (RL) value of MoS2–PANI was ? 40.79 dB at 14.01 GHz with the thickness of 2.0 mm, and the maximum effective absorption bandwidth was 5.02 GHz ranging from 11.88 to 16.90 GHz with a thickness of 2.0 mm. Moreover, the RL value of MoS2–PANI composites could reach under ? 10 dB in a wide frequency range of 4.74–18 GHz with a thickness of 1.5–4.5 mm. In particular, the 3 mm wave attenuation properties of MoS2–PANI composites were investigated for the first time, and the maximum attenuation value reached 15.45 dB. As a result, MoS2–PANI composites are promising to be excellent EM wave absorption materials in broadband.
关键词： Electromagnetic wave absorption,Broadband absorbing material,MoS2–PANI composites,Chemical oxidative polymerization,Impedance match
更新于2025-09-10 09:29:36
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Detection of Benzene and Volatile Aromatic Compounds by Molecularly Imprinted Polymer Coated Quartz Crystal Microbalance Sensor
摘要： The detection of benzene and its analogues are important but difficult without using expensive extremely analytical instruments. The present work reports the detection of aromatic hydrocarbons like benzene, toluene and isomers of xylene using quartz crystal microbalance (QCM) sensor. The surface of a silver-coated quartz crystal was coated with a simple solution drop coating method and thermally polymerized in an inert atmosphere for the formation of the sensing film. The polymer was synthesized by copolymerization of the optimum ratio of styrene, divinylbenzene and tung oil at 90°C with template. 1, 2, 3 trimethoxybenzene as template performed most efficiently for all the hydrocarbons. Linear calibration curves were observed for all the vapors in the concentration range between approximately as 1.645 to 2.605 Hz/ppm. For benzene, the sensitivity is 2.605 Hz /ppm which is the highest amongst the reported literature. Thus minimum concentration of benzene that can be detected is 0.98 ppm. The molecularly imprinted polymer structure and surface morphology were analyzed by FTIR spectroscopy, FESEM and AFM. The sensitivity of detection of aromatic molecule in this work by the molecularly imprinted polymer film is found to be the best amongst the reported literatures.
关键词： molecular imprinting technique,thermal polymerization,vegetable oil,Quartz Crystal Microbalance (QCM),aromatic hydrocarbons
更新于2025-09-10 09:29:36
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Wavelength-optimized Two-Photon Polymerization Using Initiators Based on Multipolar Aminostyryl-1,3,5-triazines
摘要： Two-photon induced polymerization (2PP) based 3D printing is a powerful microfabrication tool. Specialized two-photon initiators (2PIs) are critical components of the employed photosensitive polymerizable formulations. This work investigates the cooperative enhancement of two-photon absorption cross sections (σ2PA) in a series of 1,3,5-triazine-derivatives bearing 1-3 aminostyryl-donor arms, creating dipolar, quadrupolar and octupolar push-pull systems. The multipolar 2PIs were successfully prepared and characterized, σ2PA were determined using z-scan at 800 nm as well as spectrally resolved two-photon excited fluorescence measurements, and the results were compared to high-level ab initio computations. Modern tunable femtosecond lasers allow 2PP-processing at optimum wavelengths tailored to the absorption behavior of the 2PI. 2PP structuring tests revealed that while performance at 800 nm is similar, at their respective σ2PA-maxima the octupolar triazine-derivative outperforms a well-established ketone-based quadrupolar reference 2PI, with significantly lower fabrication threshold at exceedingly high writing speeds up to 200 mm/s and a broader window for ideal processing parameters.
关键词： two-photon initiators,femtosecond lasers,3D printing,two-photon induced polymerization,1,3,5-triazine-derivatives
更新于2025-09-10 09:29:36
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Direct C–H Arylation Polymerization to form Anionic Water-Soluble Poly(3,4-ethylenedioxythiophenes) with Higher Yields and Molecular Weights
摘要： A facile and environmentally benign Pd-catalyzed direct C–H arylation polymerization (DAP) has been developed for the syntheses of homo- and copolymers of anionic-group-functionalized 3,4-ethylenedioxythiophenes with high yields (up to 99%), high molecular weights, and narrow polydispersities. The effects of various Pd catalysts, phosphine ligands, and additives on the properties of the polymers have been examined. The method gives anionic poly(3,4-ethylenedioxythiophenes) with higher molecular weights than those produced by the previously reported chemical or electrochemical methods. The method was also used to synthesize polymers functionalized with carboxylic acid groups without the need for protection/deprotection steps. The resulting polymers can be processed from water or highly polar organic solvents. We also demonstrated a phosphine-free, water-mediated, Pd-catalyzed DAP. The anionic poly(3,4-ethylenedioxythiophenes) were stable in water, and are promising for applications in sensors, drug delivery, and cell engineering.
关键词： polyethylenedioxythiophenes,C–H arylation,polymerization,anionic polymers,step-economic syntheses,palladium catalysis
更新于2025-09-10 09:29:36
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Micro-Dumbbells—A Versatile Tool for Optical Tweezers
摘要： Manipulation of micro- and nano-sized objects with optical tweezers is a well-established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool operated with holographic optical tweezers. The 40 μm long dumbbell-shaped tool, fabricated with two-photon laser 3D photolithography has two beads for efficient optical trapping and a probing spike on one end. We demonstrate fluids viscosity measurements and vibration detection as examples of possible applications.
关键词： direct laser writing,3D lithography,optical tweezers,viscosity,two-photon polymerization,micro-tool,optical trapping
更新于2025-09-10 09:29:36
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[Polymers and Polymeric Composites: A Reference Series] Functional Polymers || Photo-polymerization
摘要： The synthesis of functional polymers by photopolymerization thrives on the rich tradition of industrial photochemistry. Photo-induced polymerization can be broadly divided based on the initiation mechanism as radical, cationic, and anionic photopolymerization. A wide variety of initiators, photosensitizers, and polymerizable materials have been studied for various applications. This chapter is intended to be a primer to major concepts of photopolymerization. In the beginning of the chapter, physical aspects of light matter interactions are presented followed by photochemical pathways leading to reactions. In the subsequent sections radical polymerization is discussed by introducing different types of initiating systems and polymerizable materials. Within the section on radical polymerization, visible light polymerization and thio-ene photochemistry are also discussed. The section on thiol-ene looks at the fundamentals of thiol-ene reactions, their initiation, reactivity, and advantages over other radical driven polymerizations. Cationic polymerization is covered based on the material science of ionic and nonionic photoacid generators (PAGs). This section also discusses spectral broadening of reactivity in PAGs to visible wavelengths through electron transfer sensitization and free radical promoted cationic polymerization (FRPCP). Unlike radical and cationic polymerization there are little or no reports of commercial application of anionic polymerization. However, due to typical monomers employed in anionic polymerization and the control over the extent of polymerization afforded by this techniques makes it very attractive for functional applications. The section on anionic polymerization summarizes recent developments in this field. Finally in the section about two-photon initiated polymerization, we discuss the scope of nonlinear optical phenomena in photopolymerization.
关键词： anionic polymerization,radical polymerization,two-photon absorption,photopolymerization,photoinitiators,photosensitizers,cationic polymerization
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Synthesis and characterization of TiO2 co-polymeric hydrogel
摘要： In this study, TiO2 doped acrylic acid-co-vinyl pyrrolidone (AA-co-VP) composite co-polymeric hydrogel was synthesized by free radical polymerization technique. Titanium dioxide (TiO2) were chosen because of its superior properties such as high activity, chemical stability, low cost, non-toxicity, and stability during irradiation. TiO2 doping were carried out by varying mass ratios as 0.05%, 0.5% and 1%. Conversion, cross-linking and swelling values of each hydrogel were calculated. According to swelling behavior, while TiO2 dope ratio increase, swelling value was also increased. Chemical, morphological and thermal properties of hydrogels were specified by using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDX), mapping and thermogravimetric analysis (TGA-DSC) techniques. TiO2 doping provides superior properties to co-polymeric hydrogel. Hydrogels have also characteristic properties of both acrylic acid and vinyl pyrrolidone.
关键词： SEM-EDX,hydrogel,TGA-DSC,free radical polymerization,acrylic acid-co-vinyl pyrrolidone,FTIR,TiO2,swelling behavior
更新于2025-09-09 09:28:46
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Structure and Stability of C:H:O Plasma Polymer Films Co-Polymerized Using Dimethyl Carbonate
摘要： C:H:O plasma polymer ?lms (PPFs) were deposited by means of plasma-enhanced chemical vapour deposition using the non-toxic, biodegradable organic compound dimethyl carbonate (DMC) at various plasma powers and pressures in order to control the degradation properties related to the carbonate ester group. Coating properties using pure DMC monomer vapours were compared to co-polymerized ?lms from gaseous mixtures of DMC with either ethylene (C2H4) or carbon dioxide (CO2) affecting deposition rate and chemical composition. C:H:O ?lm properties were found to depend primarily on the amount of oxygen in the plasma. To investigate the PPF stability during aging, changes in the composition and properties were studied during their storage both in air and in distilled water over extended periods up to 5 months. It was shown that aging of the ?lms is mostly due to oxidation of the plasma polymer matrix yielding slow degradation and decomposition. The aging processes and their rate are dependent on the intrinsic amount of oxygen in the as-prepared C:H:O ?lms which in turn depends on the experimental conditions and the working gas mixture. Adjustable ?lm properties were mainly attained using a pure DMC plasma considering both gas phase and surface processes. It is thus possible to prepare C:H:O PPFs with controllable degradability both in air and in water.
关键词： plasma polymerization,aging,degradability,thin ?lms,chemical composition
更新于2025-09-09 09:28:46
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The Impact of Polymer Grafting from a Graphene Oxide Surface on Its Compatibility with a PDMS Matrix and the Light-Induced Actuation of the Composites
摘要： Poly(dimethyl siloxane) (PDMS)-based materials with improved photoactuation properties were prepared by the incorporation of polymer-grafted graphene oxide particles. The modification of the graphene oxide (GO) surface was achieved via a surface initiated atom transfer radical polymerization (SI ATRP) of methyl methacrylate and butyl methacrylate. The modification was confirmed by thermogravimetric analysis, infrared spectroscopy and electron microscopy. The GO surface reduction during the SI ATRP was investigated using Raman spectroscopy and conductivity measurements. Contact angle measurements, dielectric spectroscopy and dynamic mechanical analyses were used to investigate the compatibility of the GO filler with the PDMS matrix and the influence of the GO surface modification on its physical properties and the interactions with the matrix. Finally, the thermal conductivity and photoactuation properties of the PDMS matrix and composites were compared. The incorporation of GO with grafted polymer chains, especially poly(n-butyl methacrylate), into the PDMS matrix improved the compatibility of the GO filler with the matrix, increased the energy dissipation due to the improved flexibility of the PDMS chains, enhanced the damping behavior and increased the thermal conductivity. All the changes in the properties positively affected the photoactuation behavior of the PDMS composites containing polymer-grafted GO.
关键词： grafting method,reversible deactivation radical polymerization,smart polymers
更新于2025-09-09 09:28:46
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Phenol-functionalized polymerization control additives for negative tone epoxide crosslinking molecular resists
摘要： Controlling undesired polymerization in nominally unexposed regions is critical to achieving high-resolution, defect-free patterns when using negative tone molecular resists based on the crosslinking of epoxides. Two onium salt additives, a photodecomposable nucleophile (PDN) and a photoacid generator (PAG), were functionalized with phenols in order to investigate their use as generalized additives capable of slowing crosslinking and improving the resolution of a variety of epoxide resists. Presented here is a phenol-functionalized PDN [tris(4-hydroxyphenyl)sulfonium tri?ate (TPS-OH-Tf )] and a phenol-functionalized PAG [tris(4-hydroxyphenyl)sulfonium antimonate (TPS-OH-SbF6)] used in combination with a model epoxide resist (4-Ep). Utilizing additives that contained phenols resulted in a decrease in resist sensitivity, but enabled higher additive loadings which could be used to offset this loss in sensitivity. Using TPS-OH-SbF6 did not provide enough polymerization control to prevent line broadening, and the use of TPS-OH-Tf was still required to achieve sub 35 nm 1:1 line:space patterns. Adding TPS-OH-Tf was also found to improve pattern collapse behavior at reduced (<25 nm) feature sizes. Initial patterning using 100 keV electron-beam lithography showed that the resolution of 4-Ep was improved to 15 nm 1:1 line:space patterns using these phenol-functionalized additives and demonstrate the potential of these additives to improve the resolution of a variety of epoxide crosslinking molecular resists.
关键词： phenol-functionalized additives,polymerization control,molecular resists,negative tone epoxide crosslinking,high-resolution patterning
更新于2025-09-09 09:28:46