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Avalia??o do grau de convers?o de resinas compostas fotoativadas em diferentes tempos e potências
摘要： Introduction: Adequate polymerization is a crucial factor in obtaining optimal physical properties and clinical performance of composite resins. Objective: To evaluate the degree of conversion (DC) and hardness of composite resins photoactivated in different power densities and curing times. Materials and method: Eighty (n=80) composite resin specimens (FiltekTM Z350 XT color A2B) with 4 mm of diameter and 2 mm of thickness were produced, whereas forty (n=40) were meant for the evaluation of degree of conversion and forty (n=40) for hardness. Ten (n=10) specimens were produced for each group assessed, whereas five were meant for the evaluation of the degree of conversion and five for hardness (P10T2; P7T2; P4T2; P1T2; P10T4; P7T4; P4T4; P1T4). Resins of the degree of conversion and hardness were photoactivated by LED for 20 seconds at power intensities of 1000 mW/cm2, 700 mW/cm2, 400 mW/cm2, and 100 mW/cm2, for groups P10T2, P7T2, P4T2, and P1T2, respectively. Groups P10T4, P7T4, P4T4, and P1T4 were cured in the same power intensity, but for 40 seconds. Result: Regarding the degree of conversion, P1T2 resins had the lowest mean value of 22.67 %, and P10T4 resins had the highest mean value of 87.9%. As for hardness, P1T2 resins also had the lowest mean of 30.93 kgf/mm2, and P10T4 had the highest mean of 82.02 kgf/mm2. Conclusion: The higher the power of the curing unit, the higher the DC and hardness of composites resins. The results of this study suggest that a device with intensity of 100 mW/cm2 does not provide satisfactory degree of conversion and hardness, compromising the performance of the restorative material.
关键词： Composite resins,Hardness,Polymerization
更新于2025-09-19 17:15:36
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Surface grafting of fluorescent polymers on halloysite nanotubes through metal-free light-induced controlled polymerization: Preparation, characterization and biological imaging
摘要： Halloysite nanotubes (HNTs) are a kind of aluminosilicate clay with a unique hollow tubular structure that has been intensively explored for various applications especially in biomedical fields owing to their excellent biocompatibility, biodegrading potential and low cost. Surface modification of HNTs with functional polymers will greatly improve their properties and endow new functions for biomedical applications. In this work, a light-induced reversible addition-fragmentation chain transfer (RAFT) polymerization was introduced to successfully prepare HNTs based fluorescent HNTs/poly(PEGMA-Fl) composites in the presence of oxygen using diacrylate-fluorescein and poly (ethylene glycol) methyl ether methacrylate (PEGMA) as the monomers. Without other catalysts, heating, and deoxygenation procedure, the polymerization process can take place under mild conditions. Besides, owing to the introduction of fluorescein and PEGMA on the surface of HNTs, the resultant HNTs/poly(PEGMA-Fl) composites display high water dispersibility and stable fluorescence. The results from cell viability examination and confocal laser scanning microscopy also demonstrated that HNTs/poly(PEGMA-Fl) composites could be internalized by L929 cells with bright fluorescence and low cytotoxicity. Taken together, we developed a novel photo-initiated RAFT polymerization method for the fabrication of HNTs based fluorescent polymeric composites with great potential for biomedical applications. More importantly, many other multifunctional HNTs based polymer composites could also be fabricated through a similar strategy owing to good designability of RAFT polymerization.
关键词： fluorescent composites,biomedical applications,Halloysite nanotubes,light-induced polymerization,surface-initiated RAFT polymerization
更新于2025-09-19 17:13:59
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Controlled synthesis of azobenzene-containing block copolymers both in the main- and side-chain from SET-LRP polymers via ADMET polymerization
摘要： Novel ABA triblock copolymer contained azobenzene (azo) chromophores both in the main- and side-chain was designed and synthesized via combination of single electron transfer-living radical polymerization (SET-LRP) and acyclic diene metathesis (ADMET) polymerization. The α-bromoester end group of side-chain azo-polymer prepared in SET-LRP system using acrylate bearing azo group as monomer was reacted with potassium acrylate to yield azo-polymer with the chain end of α-acrylate, which acted as a monofunctional macromolecular chain stopper for subsequent ADMET polymerization of azo-functionalized α,ω-diene monomer to finally controllable synthesize ABA triblock azo-copolymer. The diluted solutions of main-chain ADMET azo-homopolymer, side-chain SET-LRP azo-homopolymer, and main-side chains azo-copolymer exhibited different photoisomerization behaviors (maximum absorption and rate of photoisomerization) under the irradiation of UV and visible light. All these interesting results could provide a guide for the design of photosensitive materials.
关键词： photoresponsive polymer,Single electron transfer-living radical polymerization,acyclic diene metathesis polymerization
更新于2025-09-19 17:13:59
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Eco-friendly synthesis of regioregular poly(3-hexylthiophene) by direct arylation polymerization: Analysis of the properties that determine its performance in BHJ solar cells
摘要： A series of regioregular poly(3-hexylthiophenes) (rr-P3HTs) was synthetized by optimizing an eco-friendly Direct Arylation Polymerization (DArP) method, using as novel strategy, a gradual catalyst addition and temperature reaction increase improving P3HT quality. The polymers were analyzed and tested in organic solar cells (OSCs) in order to correlate the P3HTs properties with the power conversion efficiency (PCE). Results revealed that the best PCEs (3.6 and 3.4 %) were reached with P3HTs of the highest RR (94 and 93 % HT), with the lowest molecular weight (5.1 and 4.9 kDa) and, as X-ray diffraction in films and 2D-GIWAXS results endorse, with an edge-on orientation over the substrate, the largest size crystal and the highest Bragg’s peaks, this latter feature could be the most effective reason to obtain the best PCEs. Theoretical calculations helped to understand how specific P3HT crystalline arrangements in the active layer favors the PCE.
关键词： X-ray diffraction,Poly(3-hexylthiophene),organic solar cells,eco-friendly direct heteroarylation polymerization
更新于2025-09-19 17:13:59
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Photocontrolled Iodine-Mediated Green Reversible-Deactivation Radical Polymerization of Methacrylates: Effect of Water in the Polymerization System
摘要： Photocontrolled iodine-mediated reversible-deactivation radical polymerization (RDRP) is a facile and highly efficient access to precision polymers. Herein, a facile photocontrolled iodine-mediated green RDRP strategy was successfully established in water by using 2-iodo-2-methylpropionitrile (CP-I) as the initiator and water-soluble functional monomers including poly(ethylene glycol) methyl ether methacrylate (PEGMA), 2-hydroxyethyl methacrylate (HEMA), and 2-hydroxypropyl methacrylate (HPMA) as the model monomers under blue-light-emitting diode (LED) irradiation at room temperature. Well-defined polymers (PPEGMA, PHEMA, PHPMA) with narrow polydispersities (1.09?1.21) were obtained, and amphiphilic block copolymers which can form nanospheres in situ in water (PPEGMA-b-poly(benzyl methacrylate) (PPEGMA-b-PBnMA) and PPEGMA-b-PHPMA) were prepared. To explore the role of water in our polymerization, control experiments were successfully carried out by using oil-soluble monomer methyl methacrylate (MMA) with the help of trace amounts of water. Notably, the green solvent—water—has an additionally positive effect in accelerating the polymerization and makes our polymerization system an environmentally friendly polymerization system. Therefore, this simple strategy conducted in the presence of water enables the green preparation of well-defined water-soluble or water-insoluble polymers and clean synthesis of amphiphilic copolymer nanoparticles in situ.
关键词： blue-light-emitting diode,water-soluble functional monomers,amphiphilic block copolymers,green solvent,RDRP,Photocontrolled iodine-mediated reversible-deactivation radical polymerization
更新于2025-09-19 17:13:59
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Trace level toxic ammonia gas sensing of single-walled carbon nanotubes wrapped polyaniline nanofibers
摘要： This paper presents a two-step enhancement and a comprehensive analysis of single-walled carbon nanotubes (SWCNTs) wrapped polyaniline nanofiber (NPANI) ammonia (NH3) gas sensor at room temperature. SWCNT-PANI composites are successfully synthesized using an efficient and cost-effective rapid in situ chemical polymerization method. The structural morphology and modification of the samples are characterized using field-emission scanning electron microscopy and HRTEM. FTIR and Raman spectroscopic studies are also performed to gain a better insight into the chemical environmental interaction in the as-prepared nanocomposite. The analysis confirms the successful formation of the nanocomposite. The observed NH3 gas-sensing response at 10 ppm of SWCNT, f-SWCNT (functionalised SWCNT), and SWCNT-PANI composite sensors are 5%–6%, 18%–20%, and 24%–25%, respectively. The SWCNT-PANI composite sensors have shown higher repeatability, selectivity, long-term stability, and fast response-recovery characteristics as compared to f-SWCNTs and pristine SWCNT sensors. Concentration and temperature dependent gas-sensing studies are also analyzed. The sensor response also shows a linear relationship with NH3 gas concentration and an inverse relationship with increasing temperature.
关键词： Raman spectroscopy,rapid in situ chemical polymerization,ammonia gas sensor,polyaniline nanofiber,field-emission scanning electron microscopy,FTIR,HRTEM,room temperature,single-walled carbon nanotubes
更新于2025-09-19 17:13:59
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A Polymerizationa??Assisted Grain Growth Strategy for Efficient and Stable Perovskite Solar Cells
摘要： Intrinsically, detrimental defects accumulating at the surface and grain boundaries limit both the performance and stability of perovskite solar cells. Small molecules and bulkier polymers with functional groups are utilized to passivate these ionic defects but usually suffer from volatility and precipitation issues, respectively. Here, starting from the addition of small monomers in the PbI2 precursor, a polymerization-assisted grain growth strategy is introduced in the sequential deposition method. With a polymerization process triggered during the PbI2 film annealing, the bulkier polymers formed will be adhered to the grain boundaries, retaining the previously established interactions with PbI2. After perovskite formation, the polymers anchored on the boundaries can effectively passivate undercoordinated lead ions and reduce the defect density. As a result, a champion power conversion efficiency (PCE) of 23.0% is obtained, together with a prolonged lifetime where 85.7% and 91.8% of the initial PCE remain after 504 h continuous illumination and 2208 h shelf storage, respectively.
关键词： polymerization,defect passivation,intermolecular exchanging grain growth,dimethyl itaconate,perovskite solar cells
更新于2025-09-19 17:13:59
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A Facile and Versatile Synthesis of Enda??Functionalized Poly(phenylacetylene)s: A Multicomponent Catalytic System for Wella??Controlled Living Polymerization of Phenylacetylenes
摘要： A rhodium-based multicomponent catalytic system for well-controlled living polymerization of phenylacetylenes has been developed. The catalytic system is composed of easily available and bench-stable [Rh(nbd)Cl]2, aryl boronic acid derivatives, diphenylacetylene, 50% aq KOH, and PPh3. This system offers a method for facile and versatile synthesis of various end-functionalized cis-stereoregular poly(phenylacetylene)s because components from aryl boronic acids and diphenylacetylene were introduced to the initiating end of the polymers. The polymerization reaction shows a typical living nature with a high initiation efficiency, and the molecular weight of the resulting poly(phenylacetylene)s can be easily controlled with very narrow molecular weight distributions (Mw/Mn = 1.02–1.09). The experimental facts suggest that the present catalytic system has the higher polymerization activity than the polymerization activities of other rhodium-based catalytic systems previously reported.
关键词： Living polymerization,Rhodium,Boronic acids,Phenylacetylenes,Polymers
更新于2025-09-19 17:13:59
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Organic Electropolymerized Multilayers for Light-Emitting Diodes and Displays
摘要： In electrochemistry, the carbazole generally coupled to dimer but not polymer. This work has reported that organic electropolymerzation (OEP) of 4,4',4"-Tri(N-carbazolyl)triphenylamine (TCTA) would form high crosslinked carbazole polymer by its high activity/reversibility and a synchronous viscosity control. It has significantly improved the OEP film quality of both holes transporting and electroluminescent layers in organic light emitting diodes. As a result, the conductivity and power efficiency of the organic light emitting diodes with TCTA are eight and four times of that without TCTA. A prototype display device with 1.7 inch monochrome passive matrix of 58 ppi under driving chip is successfully fabricated with accurate pixel size and uniform electroluminescence, which makes the big potential of organic electropolymerzation in the electroluminescent application.
关键词： TCTA,Polymerization,Electrochemistry,Carbazole,Organic Light emitting diodes
更新于2025-09-19 17:13:59
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Light-induced Polymer Response Through Thermoplasmonics Transduction in Highly Monodisperse Core-Shell-Brush Nanosystems
摘要： Smart nanosystems that transduce external stimuli to physical changes are an inspiring challenge in current materials chemistry. Hybrid organic-inorganic materials attract great attention due to the combination of building blocks responsive to specific external solicitations. In this work, we present a sequential method for obtaining an integrated core-shell-brush nanosystem that transduces light irradiation into a particle size change through a thermoplasmonic effect. We first synthetize hybrid monodisperse systems made up of functionalized silica colloids covered with controllable thermo-responsive Poly(N-isopropylacrylamide), PNIPAm, brushes, produced through radical photopolymerization. This methodology was successfully transferred to Au@SiO2 nanoparticles, leading to a core-shell-brush architecture, in which the Au core acts as a nano-source of heat; the silica layer, in turn, adapts the metal and polymer interfacial chemistries and can also host a fluorescent dye for bioimaging. Upon green LED irradiation, a light-to-heat conversion process leads to the shrinkage of the external polymer layer, as proven by in situ DLS. Our results demonstrate that modular hybrid nanosystems can be designed and produced with photo-thermo-physical transduction. These remote-controlled nanosystems present prospective applications in smart carriers, responsive bioscaffolds or soft robotics.
关键词： photothermal effect,hybrid materials,in-situ DLS,UV-photo induced polymerization,core-shell-brush colloids,Smart nanosystems
更新于2025-09-19 17:13:59