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Crosslink network and phenyl content on the optical, hardness, and thermal aging of PDMS LED encapsulant
摘要： This work aims to synthesize new series of polysiloxane copolymer through hydrosilylation reaction based on different level of crosslink densities and phenyl content. The results revealed that polysiloxanes resins with phenyl rings increased viscosity up to 3800 cps while displaying a relatively high refractive index of 1.531. The asymmetric phenyl substitution onto chain backbone led to formation of densely packed structure resulting in reduced water absorption and gas permeability of PDMS resins. High level of crosslinking contributed to a high shore A hardness and adhesion strength. It displayed transparency of 97% whose percentage reduction was 1.6% under thermal and 0.6% UV aging. No obvious discoloration was observed during accelerated thermal aging up to 210 min at 80 (cid:1)C. These results are key attributes that make the synthesized polysiloxane series as ideal candidate for high brightness LED encapsulant. ? 2019 Wiley Periodicals, Inc. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47895.
关键词： copolymers,thermal properties,ring-opening polymerization,optical properties,synthesis and processing techniques
更新于2025-11-19 16:56:42
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Structure, Reactivity, Nonlinear Optical Properties and Vibrational Study of 5-Thioxo-1,4-thiazaolidin-3-one and 5-thioxo-1,4,2-thiazasilolidin-3-one (Silicon vs. Carbon). A DFT Study
摘要： The structures and nonlinear optical properties (NLO) of 5-thioxo-1,4-thiazaolidin-3-one(Rhodanine) and 5-thioxo-1,4,2-thiazasilolidin-3-one (silarhodanine) tautomers were studied in gas phase and in solutions using the B3LYP density functional theory and composite CBS-QB3 method. The global minimum at the B3LYP/6-31++G(d,p) and CBS-QB3 levels of theory is tautomer 5 in the gas phase and in solvents for rhodanine, and simiarly, tautomer 13 is the global minimum for silarhodanine. The interconversion among the tautomers is proceeded by an intramolecular proton transfer reaction. An identical solvent effects can be noted for rhodanine and silarhodanine tautomers. The activation barrier towards ring-opening processes (1→2, 9→10) decreases with the increasing dielectric constant of the solvent; on the other hand, the barrier of the ring-closure processes (2→3, 10→11) increases with the increasing dielectric constant. The tautomers are predicted to show significant NLO properties. Also, a number of correlations between the dipole moment and electron densities in bond critical points of the S3-C4 bond and interaction energy as well as vibrational frequencies at the transition states (TS2–3,TS10–11) were examined under different solvents. Finally, the investigation of the heavy atom substitution effects on the properties of silarhodanine is proven to be very weak under these conditions.
关键词： Vibrational assignments,Silarhodanine,Reactivity,Rhodanine,NLO,Ring-opening,Solvent effects
更新于2025-09-23 15:23:52
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Photoresponsive Circular Supramolecular Polymers: Topological Trap and Photoinduced Ring-opening Elongation
摘要： Topological features of one-dimensional macromolecular chains govern the properties and functionality of natural and synthetic polymers. To address this issue in supramolecular polymers, we have synthesized two topologically distinct supramolecular polymers with intrinsic curvature, i.e., circular and helically folded nanofibers, from azobenzene-functionalized supramolecular rosettes. When a mixture of circular and helically folded nanofibers was exposed to UV light, a selective unfolding of the latter open-ended supramolecular polymers was observed as a result of the curvature-impairing internal force produced by the trans-to-cis photoisomerization of the azobenzene. This distinct sensitivity suggests that the topological features of supramolecular polymers define their mechanical stability. Furthermore, the exposure of circular supramolecular polymers in more polar media to UV irradiation resulted in a ring-opening followed by a chain elongation, demonstrating that the circular supramolecular polymer can work as a topological kinetic trap.
关键词： topology,ring opening,azobenzene,supramolecular polymer,photoisomerization
更新于2025-09-23 15:23:52
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Next‐generation quantum theory of atoms in molecules for the ground and excited state of the ring‐opening of cyclohexadiene
摘要： The factors underlying the experimentally observed branching ratio (70:30) of the (1,3-cyclohexadiene) CHD ! HT (1,3,5-hexatriene) photochemical ring-opening reaction are investigated. The ring-opening reaction path is optimized by a high-level multi-reference DFT method and the density along the path is analyzed by the quantum theory of atoms in molecules (QTAIM) and stress tensor methods. The performed density analysis suggests that, in both S1 and S0 electronic states, there exists an attractive interaction between the ends of the fissile σ-bond of CHD that steers the ring-opening reaction predominantly in the direction of restoration of the ring. It is suggested that opening of the ring and formation of the reaction product (HT) can only be achieved when there is a sufficient persistent nuclear momentum in the direction of stretching of the fissile bond. As this orientation of the nuclear momentum vector can be expected relatively rare during the dynamics, this explains the observed low quantum yield of the ring-opening reaction.
关键词： QTAIM,ring-opening,cyclohexadiene,conical intersection,stress tensor
更新于2025-09-23 15:23:52
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A novel ratiometric and colorimetric fluorescent probe for hydrazine based on ring-opening reaction and its applications
摘要： In recent years, with the increasing awareness of environmental protection, the detection of industrial emissions has become more and more strict. Hydrazine, as a common reactive group, the excessive emissions by the widespread use is inevitably harmful to the environment and human beings. To respond positively to environment protection policies at home and abroad, the development of a convenient and effective hydrazine probe has become an important subject for many research groups. In this work, a derivative containing lactone ring was synthesized based on naphthalimide. This probe displayed a fast colorimetric and ratiometric fluorescent response for hydrazine with high selectivity and sensitivity based on the ring-opening reaction. The detection limit of the probe for hydrazine is about 0.2032 μM (< 10 ppb). It is worth mentioning that the probe can successfully apply to detect gaseous hydrazine when the probe is loaded on the periopaper. Furthermore, the results of biological imaging experiment indicated that the probe can detect the hydrazine at the cellular level.
关键词： Cell imaging,Lactone ring,Hydrazine,Ring-opening,Ratiometric and colorimetric
更新于2025-09-23 15:22:29
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Synthesis of High Performance Cyclic Olefin Polymers (COPs) with Ester Group via Ring-Opening Metathesis Polymerization
摘要： Novel ester group functionalized cyclic olefin polymers (COPs) with high glass transition temperature, high transparency, good mechanical performance and excellent film forming ability have been achieved in this work via efficient ring-opening metathesis copolymerization of exo-1,4,4a,9,9a,10-hexahydro-9,10(1′,2′)-benzeno-l,4-methanoanthracene (HBM) and comonomers (5-norbornene-2-yl methylacetate (NMA), 5-norbornene-2-yl methyl 2-ethylhexanoate (NME) or 5-norbornene-2-yl methyldodecanoate (NMD)) utilizing the Grubbs first generation catalyst, Ru(CHPh)(Cl)2(PCy3)2 (Cy = cyclohexyl, G1), followed by hydrogenation of double bonds in the main chain. The fully hydrogenated copolymers were characterized by nuclear magnetic resonance, FT-IR spectroscopy analysis, gel permeation chromatography, and thermo gravimetric analysis. Differential scanning calorimetry curves showed that the glass transition temperatures (Tg) linearly decreased with the increasing of comonomers content, which was easily controlled by changing feed ratios of HBM and comonomers. Static water contact angles tests indicate that hydrophilicity of copolymers can also be modulated by changing the comonomers incorporation. Additionally, the mechanical performances of copolymers were also investigated.
关键词： dimensional stability,optical materials,COPs (cyclic olefin polymers),ROMP (ring-opening metathesis polymerization),hydrophilicity
更新于2025-09-23 15:22:29
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Synthesis, characterization and nanoaggregates of alkyl and triethylene glycol substituted 3,6-carbazolevinylenes homopolymers and block copolymers
摘要： Ring strained carbazolephanedienes containing octyl and triethylene glycol chains have been prepared by the McMurry coupling reaction of their corresponding dialdehydes. A series of well-defined carbazolevinylene homopolymers and block polymers containing octyl and triethylene glycol chains have been synthesized through ring-opening metathesis polymerization of the corresponding carbazolephanedienes using the third generation Grubbs initiator. The optical and electrochemical properties and morphologies of the homopolymers and block copolymers with different block ratios such as 1:1, 3:1 and 1:3 have been investigated. The bandgap of the polymers is relatively low (2.64–2.79 eV) and is strongly dependent on the side chains. The carbazolevinylene block copolymers with higher composition of the triethylene glycol substituted carbazolevinylene block showed sphere-like nanoaggregates due to the highly disorder and flexibility of the triethylene glycol chains. This work demonstrated well control of the polymer microstructures with specific nanoaggregates in solid state.
关键词： Sphere-like nanoaggregates,Carbazolephanedienes,Polymer microstructures,Ring-opening metathesis polymerization,Carbazolevinylene polymers
更新于2025-09-19 17:15:36
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Fluorescence sensing and intracellular imaging of Pd2+ ion by a novel coumarinyl-rhodamine Schiff base
摘要： Coumarinyl-rhodamine, HCR, serves as extremely selective sensor to Pd2+ ion in ethanol/H2O (8:2, v/v, HEPES buffer, pH 7.2) solution and the limit of detection (LOD) is 18.8 nM (3σ method). The free sensor, HCR, is weakly emissive and in presence of Pd2+, the colour changes from straw to pink with very strong emission at 598 nm in presence of eighteen other cations. The plausible mechanism includes opening of the spirolactam ring of rhodamine upon interaction with Pd2+. This is justified by a structure optimization and transition energy calculation by DFT technique. HCR undergoes 1:1 complexation with Pd2+ that has been confirmed via Job’s plot, mass spectra and Bensei-Hildebrand plot (association constant Ka, 9.1×10^4 M^-1). A separate in vitro experiment shows that HCR can specifically perceive Pd2+ in MCF7 (Human breast adenocarcinoma) cell lines.
关键词： Coumarinyl-rhodamine,spirolactam ring opening,DFT computation,Pd2+-sensor,live cell imaging
更新于2025-09-19 17:15:36
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Thiol–ene click reaction-induced fluorescence enhancement by altering the radiative rate for assaying butyrylcholinesterase activity
摘要： Bis‐ligated, homoleptic magnesium complexes 1–3 were synthesized through the reaction of 1 equiv. dibutyl magnesium with 2 equiv. β‐ketiminato ligands bearing different substituents on the nitrogen atom and 8 position on benzocyclohexanone. All of the complexes were identified by nuclear magnetic resonance (NMR) and X‐ray crystallography. Complexes 2 and 3 adopted distorted tetrahedral geometry around Mg, by chelating of two ancillary ligands, while complex 1 adopted a dimeric structure with penta‐coordination around Mg. These complexes can be used as efficient catalysts for ring‐opening polymerization of L‐lactide, ε‐caprolactone, δ‐valerolactone (δ‐VL) and trimethylene carbonate in the presence of alcohol as a co‐initiator. With the increasing steric bulk of the ancillary ligands, the catalytic activity of Mg complexes was improved significantly. Particularly, complex 3 having the largest steric hindrance showed excellent catalytic performance for the polymerization of δ‐VL. It could polymerize 800 equiv. δ‐VL in 10 min, and produce polyvalerolactone with narrow molecular weight distributions (Mw/Mn < 1.2) at 35°C or higher temperature. No transesterification side reaction was observed. Moreover, complex 3 exhibited good tolerance to excessive alcohol and an immortal polymerization characteristic. The mechanism studies by in situ NMR demonstrated a coordination‐insertion process. Besides, it revealed that the steric bulky substituents in the active species derived from the complex and alcohol prevented the metal center from deactivation.
关键词： ring‐opening polymerization,magnesium complex,polyester,δ‐valerolactone,bis‐ligated
更新于2025-09-19 17:15:36
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<i>ipso</i> -Arylative Ring-Opening Polymerization as a Route to Electron-Deficient Conjugated Polymers
摘要： ipso-Arylative ring-opening polymerization of 2-bromo-8-aryl-8H-indeno[2,1-b]thiophen-8-ol monomers proceeds to Mn up to 9 kg mol(cid:2)1 with conversion of the monomer diarylcarbinol groups to pendent conjugated aroylphenyl side chains (2-benzoylphenyl or 2-(4-hexylbenzoyl)phenyl), which influence the optical and electronic properties of the resulting polythiophenes. Poly(3-(2-(4-hexylbenzoyl)phenyl)thiophene) was found to have lower frontier orbital energy levels (HOMO/LUMO = (cid:2)5.9/(cid:2)4.0 eV) than poly(3-hexylthiophene) owing to the electron-withdrawing ability of the aryl ketone side chains. The electron mobility (ca. 2 (cid:2) 10(cid:2)3 cm2 V(cid:2)1 s(cid:2)1) for poly(3-(2-(4-hexylbenzoyl)phenyl)thiophene) was found to be significantly higher than the hole mobility (ca. 8 (cid:2) 10(cid:2)6 cm2 V(cid:2)1 s(cid:2)1), which suggests such polymers are candidates for n-type organic semiconductors. Density functional theory calculations suggest that backbone distortion resulting from side-chain steric interactions could be a key factor influencing charge mobilities.
关键词： ipso-arylative polymerization,ring-opening polymerization,conducting materials,cross-coupling,palladium
更新于2025-09-10 09:29:36