Enthalpy Relaxation Study of Poly(Vinyl Chloride) Films Based on the Time-Temperature Superposition Principle

Abstract

In the enthalpy relaxation of poly(vinyl chloride), a decrease in enthalpy upon the isothermal ageing was measured using the differential scanning calorimetry method as a function of ageing time (t_A) and ageing temperature. The range of the ageing temperature was from 56?°C (T_g ? 25?°C) to 72?°C (T_g ? 9?°C) where T_g denotes the glass transition temperature. The limiting value of the decrease in enthalpy was determined by applying a stretched exponential function to the measured enthalpy data. The relaxation function (?) was derived from the measured enthalpy and the construction of a master curve was tried by shifting the ? ? t_A curves of the respective ageing temperatures horizontally. Although there was no agreement between the shift factors (a_T) and the relaxation times of the ? ? t_A curves, the superposition was successfully constructed and the a_T values obtained for the poly(vinyl chloride) sample were found to be comparable to those reported for viscoelastic experiments over a broad temperature range above and below T_g carried out for different polymers. The origin of the decrease in enthalpy was briefly discussed in terms of the chain dynamics in the isothermal condition.     

Transition‐Metal‐Free Trifluoromethylthiolation of N‐Heteroarenes

A general and efficient methodology for the direct transition metal free trifluoromethylthiolation of a broad range of biologically relevant N‐heteroarenes is reported employing abundant sodium chloride as the catalyst. This method is operationally simple, exhibits high functional group tolerance, and does not require protecting groups.     

基于有序介孔碳的氯离子选择性电极的制备及其在手持传感系统中的应用

以有序介孔碳(OMC)球为离子-电子转换层,制备了固态氯离子选择性电极,构建了基于离子敏感的场效应晶体管(ISFET)的手持式传感系统,用于检测人体血清中的氯离子。优化了OMC前驱体的碳化温度,探究了OMC形貌结构对电极传感性能的影响;电极柔性化制备后考察了其在手持系统中对氯离子的检测效果。结果表明,最优条件下,电极在5.12×10^-4~1.02 mol/L的浓度范围呈现线性响应,响应斜率为60 mV/decade。该柔性电极在手持传感系统中展现出高灵敏度和重现性,可用于人体血清样品中氯离子的检测,其回收率为96.3%~104.9%。     

胆碱氧化酶功能化室温磷光量子点的制备及其对氯化胆碱的定量检测

环境友好型纳米生物传感器能够提高传统生物分子传感器的检测性能，在实际应用中具有重要的应用价值。本研究以胆碱氧化酶（ChOx）为模板，在室温（25 ℃）下通过矿化作用制备了一种ChOx功能化的室温磷光（RTP）量子点（QDs）（ChOx RTP QDs）纳米生物传感器，并利用ChOx与氯化胆碱的特异性酶-底物反应和光诱导的电子转移（PIET）实现了对氯化胆碱（Cho）的RTP定量检测。该纳米生物传感器对氯化胆碱检测的线性范围为0.05~20 mmol/L，检出限为0.02 mmol/L。该方法基于QDs的RTP性质，可以有效地避免生物样品背景荧光的干扰，且无需复杂的样品前处理过程，因此该方法较适合于生物样品中氯化胆碱的定量检测。     

高温水解-离子色谱法测定钴酸锂中氯

使用高温水解-离子色谱法对钴酸锂中痕量的氯进行分析测定。样品在1 100℃高温下通入氧气与水蒸气进行水解反应,生成氯化氢气体随载气带出,经冷凝后接收,并通过离子色谱法对氯的含量进行测定。以NaHCO3(4.5mmol/L)与Na2CO3(2.7mmol/L)的混合溶液为淋洗液,经SH-AG-1保护柱及SH-AC-1分离柱分离,Cl-在0.05~5.00mg/L范围内浓度与峰面积呈线性关系,检出限(3S)为0.010mg/L。方法测定氯的加标回收率在92%~96%,相对标准偏差(n=11)在3.0%~5.3%,方法准确、可靠。     

Unusual 4‐arsonoanilinium cationic species in the hydrochloride salt of (4‐aminophenyl)arsonic acid and formed in the reaction of the acid with copper(II) sulfate,copper(II) chloride and cadmium chloride

Structures having the unusual protonated 4‐arsonoanilinium species, namely in the hydrochloride salt, C₆H₉AsNO₃⁺·Cl⁻, (I), and the complex salts formed from the reaction of (4‐aminophenyl)arsonic acid (p‐arsanilic acid) with copper(II) sulfate, i.e. hexaaquacopper(II) bis(4‐arsonoanilinium) disulfate dihydrate, (C₆H₉AsNO₃)₂[Cu(H₂O)₆](SO₄)₂·2H₂O, (II), with copper(II) chloride, i.e. poly[bis(4‐arsonoanilinium) [tetra‐μ‐chlorido‐cuprate(II)]], {(C₆H₉AsNO₃)₂[CuCl₄]}_n , (III), and with cadmium chloride, i.e. poly[bis(4‐arsonoanilinium) [tetra‐μ‐chlorido‐cadmate(II)]], {(C₆H₉AsNO₃)₂[CdCl₄]}_n , (IV), have been determined. In (II), the two 4‐arsonoanilinium cations are accompanied by [Cu(H₂O)₆]²⁺ cations with sulfate anions. In the isotypic complex salts (III) and (IV), they act as counter‐cations to the {[CuCl₄]²⁻}_n or {[CdCl₄]²⁻}_n anionic polymer sheets, respectively. In (II), the [Cu(H₂O)₆]²⁺ ion sits on a crystallographic centre of symmetry and displays a slightly distorted octahedral coordination geometry. The asymmetric unit for (II) contains, in addition to half the [Cu(H₂O)₆]²⁺ ion, one 4‐arsonoanilinium cation, a sulfate dianion and a solvent water molecule. Extensive O—H…O and N—H…O hydrogen bonds link all the species, giving an overall three‐dimensional structure. In (III), four of the chloride ligands are related by inversion [Cu—Cl = 2.2826 (8) and 2.2990 (9) Å], with the other two sites of the tetragonally distorted octahedral CuCl₆ unit occupied by symmetry‐generated Cl‐atom donors [Cu—Cl = 2.9833 (9) Å], forming a two‐dimensional coordination polymer network substructure lying parallel to (001). In the crystal, the polymer layers are linked across [001] by a number of bridging hydrogen bonds involving N—H…Cl interactions from head‐to‐head‐linked As—O—H…O 4‐arsonoanilinium cations. A three‐dimensional network structure is formed. Cd^II compound (IV) is isotypic with Cu^II complex (III), but with the central CdCl₆ complex repeat unit having a more regular M —Cl bond‐length range [2.5232 (12)–2.6931 (10) Å] compared to that in (III). This series of compounds represents the first reported crystal structures having the protonated 4‐arsonoanilinium species.     

Influence of Potassium Metal-Support Interactions on Dendrite Growth

Combined synchrotron X-ray nanotomography imaging, cryogenic electron microscopy (cryo-EM) and modeling elucidate how potassium (K) metal-support energetics influence electrodeposit microstructure. Three model supports are employed: O-functionalized carbon cloth (potassiophilic, fully-wetted), non-functionalized cloth and Cu foil (potassiophobic, nonwetted). Nanotomography and focused ion beam (cryo-FIB) cross-sections yield complementary three-dimensional (3D) maps of cycled electrodeposits. Electrodeposit on potassiophobic support is a triphasic sponge, with fibrous dendrites covered by solid electrolyte interphase (SEI) and interspersed with nanopores (sub-10 nm to 100 nm scale). Lage cracks and voids are also a key feature. On potassiophilic support, the deposit is dense and pore-free, with uniform surface and SEI morphology. Mesoscale modeling captures the critical role of substrate-metal interaction on K metal film nucleation and growth, as well as the associated stress state.     

Synthetic K+ Channels Constructed by Rebuilding the Core Modules of Natural K+ Channels in an Artificial System

Different types of natural K⁺ channels share similar core modules and cation permeability characteristics. In this study, we have developed novel artificial K⁺ channels by rebuilding the core modules of natural K⁺ channels in artificial systems. All the channels displayed high selectivity for K⁺ over Na⁺ and exhibited a selectivity sequence of K⁺≈Rb⁺ during the transport process, which is highly consistent with the cation permeability characteristics of natural K⁺ channels. More importantly, these artificial channels could be efficiently inserted into cell membranes and mediate the transmembrane transport of K⁺, disrupting the cellular K⁺ homeostasis and eventually triggering the apoptosis of cells. These findings demonstrate that, by rebuilding the core modules of natural K⁺ channels in artificial systems, the structures, transport behaviors, and physiological functions of natural K⁺ channels can be mimicked in synthetic channels.     

氢氧化钡与氯化铵反应实验中结冰成功的关键

对氢氧化钡晶体与氯化铵晶体吸热反应进行实验改进,在反应物中加少量的水,反应小烧杯上面倒扣上一个大一点的烧杯等,使得实验中水结冰成功率高,结冰快,且结冰量增大。结冰水中加入酚酞溶液,结出的冰为红色,既能检验氨的生成,又增添了实验的趣味性。     

探究镁与氯化钠溶液反应的微观过程*

镁在常温下和水发生反应的速率较慢,这是因为镁表面存在氢氧化镁附着层的保护作用,但是镁可以和NaCl溶液发生较快的反应,在产生大量气泡的同时生成白色固体。通过对白色固体进行分析发现,在有Cl^-的环境下氢氧化镁会逐渐转化为碱式氯化镁,同时也会导致溶液pH的升高。经过实验探究发现,镁在不同浓度NaCl溶液中的反应现象存在差异,在反应过程中溶解氧含量也会下降。