苯酰亚胺结构对PET阻燃抗熔滴及抑烟的贡献

通过本体聚合方法合成了一系列侧链含苯酰亚胺结构的聚对苯二甲酸乙二酯(PET)共聚酯.研究发现,苯酰亚胺单元的引入不仅提高了共聚酯的玻璃化转变温度(T_g)和高温成炭性,并且大大降低了共聚酯高温下的热分解速率.随着苯酰亚胺含量的增加,共聚酯表现出更高的氧指数(LOI)值和更好的阻燃抗熔滴效果.锥形量热测试结果表明,苯酰亚胺结构的引入可以有效地降低共聚酯的峰值热释放速率(p-HRR)、峰值烟释放速率(p-RSR)和总烟释放量(TSR).通过对纯PET和共聚酯燃烧测试后残炭的结构和形貌分析,发现苯酰亚胺结构有助于共聚酯形成石墨化程度更高的致密炭层,这些炭层起到隔热隔氧和抑制有机可燃烟气挥发的作用,在不引入传统阻燃剂的情况下,赋予共聚酯很好的本征阻燃性及抑烟性.     

Classification of partial difference sets in Abelian groups of order $$4p^2$$

In this article we provide a complete classification of regular partial difference sets in Abelian groups of order \(4p^2\), p an odd prime. It turns out that the known examples are the only examples. These are, up to complements, the trivial examples, the PCP examples, and a sporadic example in \(\mathbb {Z}_2^2\times \mathbb {Z}_3^2\).     

Synthesis of functionalized 3-arylpyridazines via Pd-catalyzed decarboxylative cross-coupling of pyridazine-3-carboxylic acids

An efficient and general protocol for the decarboxylative cross-coupling of pyridazine-3-carboxylic acids with aryl-bromides has been described. This method provides a new avenue for the synthesis of 3-arylpyridazines via decarboxylative cross-coupling strategy by employing the dual-catalyst system of Pd(PPh₃)₄/Cu₂O in the presence of Li₂CO₃ at 160 °C in DMA.     

A facile synthesis of novel endo-selective polycyclic spiropyrrolidine oxindoles via 1,3-dipolar cycloaddition of α,γ-dialkylallenoate esters

Novel polycyclic spiropyrrolidine oxindoles that bear two vicinal quaternary centers and an exocyclic CC double bond have been synthesized by a three-component reaction involving α,γ-dialkylallenoate esters, isatin derivatives and amino acids, by way of an endo-selective 1,3-dipolar cycloaddition. These reactions proceed in high yields and diastereoselectivities. The structures and relative stereochemistry of products were confirmed by NMR, HRMS and X-ray crystallography.     

Self-Assembly of Alkylammonium Chains on Montmorillonite: Effect of Interlayer Cations,CEC, and Chain Length

Recently, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties. Especially, polymer clay nanocomposites have attracted both academic and industrial attention. Currently, the structure and physical phenomena of organoclays at molecular level are difficultly explained by existing experimental techniques. In this work, molecular dynamics (MD) simulation was executed using the CLAYFF and CHARMM force fields to evaluate the structural properties of organoclay such as basal spacing, interlayer density, energy and the arrangement of alkyl chains in the interlayer spacing. Our results are in good agreement with available experimental or other simulation data. The effects of interlayer cations (Na⁺, K⁺, Ca²⁺), the cation exchange capacity, and the alkyl chain length on the basal spacing and the structural properties are estimated. These simulations are expected to presage the microstructure of organo-montmorillonite and lead relevant engineering applications.     

DBSA-catalyzed hydrolysis of chain α-oxo ketene dithioacetals in water: Aqueous synthesis of β-ketothioesters

In this paper, we wish to report an environment friendly synthetic method for β-ketothioesters from a dodecylbenzenesulfonic acid (DBSA)-catalyzed hydrolysis reaction of chain α-oxo ketene dithioacetals in water. It was shown that the hydrolysis reaction of chain α-oxo ketene dithioacetals could efficiently occur in the presence of 7.5?mol% DBSA at 100?°C in water, affording the desired β-keto thioesters in excellent yields.     

Preparations and photophysical properties of thermally activated delayed fluorescence materials based on N-phenyl-phenothiazine-S,S-dioxide

Four compounds (TM-1～4) based on N-(4-trifluoromethylphenyl)phenothiazine-S,S-dioxide and N-[3,5-bis(trifluoromethyl)phenyl]phenothiazine-S,S-dioxide are synthesized by Buchwald-Hartwig cross coupling reaction. The effect of different substituents in acceptors on the electronic, photophysical and electrochemical properties are studied by UV–Vis, fluorescence spectroscopy, cyclic voltammetry curves and theoretical calculations. The energy gaps (ΔE_ST) between singlet excited states (S₁) and triplet excited states (T₁) of these compounds decrease by addition of one para-substituted CF₃ or two meta-substituted CF₃ on N-phenyl in order to enhance the electron-withdrawing capability of the acceptors. Small ΔE_ST of these compounds range from 0.09 eV to 0.18 eV. TM-2～4 exhibit thermally activated delayed fluorescence (TADF) characteristics with short delayed fluorescence lifetimes (τ_d) within 0.69-1.16 μs. TM-3 emits blue light with an emission wavelength of 475 nm.     

Ring-contraction from benzo[b][1,4]thiazines to benzo[d]thiazolines induced by oxygen

An unexpected ring-contraction from benzo[b]pyrazino[1,2-d][1,4]thiazine-1,4-diones (6) to benzo[4,5]thiazolo[3,2-a]pyrazine-1,4-diones (7) has been developed. The preliminary mechanistic studies showed the transformation contained two independent steps: the first step is the formation of a Michael adduct upon the addition of the protic solvent, in the presence of base, to the C-2-C-3 double bond of compound 6, and the second step is a ring-contraction induced by oxygen via the migration of sulfur atom from C-2 to C-3 position. And its scope is also studied.