亲二氧化碳碳氢聚合物及其应用*

超临界二氧化碳（scCO₂）作为一种新型“绿色溶剂”,具有无毒、不可燃、易于分离以及来源丰富等特点,有望替代传统的挥发性有机溶剂。但scCO₂是很弱的溶剂,大部分极性分子和高分子量聚合物在其中的溶解度都很低,限制了其工业应用。目前,应用scCO₂遇到的一个挑战就是寻找有效的适用于scCO₂的表面活性剂、配合物、相转移剂等。本文综述了亲二氧化碳聚合物的研究进展,从链段柔顺性和自由体积、溶质/溶质相互作用、溶质/CO₂相互作用三个方面介绍了亲二氧化碳碳氢化合物的设计原则,并介绍了亲二氧化碳聚合物在制备表面活性剂、增溶染料和催化剂等方面的相关应用。     

开关型Pickering乳液体系

Pickering乳液以胶体尺寸的固体粒子代替传统表面活性剂作为稳定剂,具有超稳定,生物相容性好以及对环境友好等优点。开关型Pickering乳液可随pH值、CO₂/N₂浓度、温度、磁场强度及光强度等条件的变化而改变固体乳化剂的表面润湿性,实现在“乳化”与“破乳”之间的快速转换,在非均相催化、乳液聚合等诸多领域有广泛的应用前景。本文全面总结了近年来开关型Pickering乳液的研究进展及其在界面催化系统、液膜处理有机废水、药物的包封与释放等方面的应用。     

改性二氧化硅纳米颗粒提高二氧化碳泡沫稳定性的研究

通过纳米二氧化硅的硅烷化改性,使其在高矿化度盐水中可以稳定存在的前提下,研究了改性纳米颗粒与阳离子表面活性剂十二烷基三甲基氯化铵混合体系的溶液稳定性及协同稳定CO₂泡沫的效果.研究结果表明,无机盐离子对改性纳米颗粒与阳离子表面活性剂间的静电吸引力具有屏蔽作用,且矿化度越高,屏蔽效果越明显,从而混合溶液更易于在高盐水中稳定;纳米颗粒表面的活性剂吸附层受二者浓度的影响,进而影响了颗粒的亲/疏水性;当混合体系中的表面活性剂浓度低于临界胶束浓度(CMC)时,混合溶液与CO₂的界面张力高于单独活性剂溶液,而当活性剂浓度高于CMC时,对CO₂-溶液界面张力几乎无影响,最低界面张力可降至6 mN/m左右;改性纳米颗粒的加入可以进一步提高CO₂体相泡沫半衰期一倍以上,但受二者浓度比例的影响;纳米颗粒的加入有效提高了多孔介质中泡沫的表观黏度,最大增幅由20 mPa·s增至55 mPa·s左右,泡沫黏度增加接近3倍,增强了CO₂泡沫驱的封堵作用.     

Sn(MSA)2电镀液体系表面活性剂性能优化的模拟研究

在本工作中,我们利用粗粒化分子动力学(MD)模拟方法,研究了两亲性表面活性剂构型及浓度对Sn(MSA)₂类电镀液体相溶液与铜基板周围电镀液微观结构的影响,从分子水平系统考察了主盐离子、表面活性剂与甲醛添加剂的分布和聚集情况,及其与铜基板的相互作用.研究表明,A₄B₁₂型表面活性剂的疏水链段(A₄)协同效应较强,易在溶液中形成胶束,在基板上吸附能力有限;A₂B₁₂A₂疏水链较短,B₆A₄B₆疏水链居中,该两种表面活性剂在溶液中难以聚集,易充分吸附于基板之上;(AB₃)₄型表面活性剂在体相溶液中充分分散,在基板上的吸附能力有限.A₂B₁₂A₂及B₆A₄B₆型表面活性剂的充分吸附,有助于金属离子及甲醛添...     

CO2在Fe3O4(111)表面的吸附结构及能量研究

利用密度泛函理论研究了CO₂在Fe₃O₄（111）表面Fe_tet1和Fe_oct2两种终结的吸附行为。在Fe_tet1终结表面,当覆盖度为1/5 ML时,CO₂倾向于线性吸附;而在高覆盖度下,弯曲的CO₂与表面O作用形成CO₃^2-结构。在Fe_oct2终结表面,CO₂倾向于弯曲吸附,在1/6 ML和1/3 ML覆盖度时都可以形成CO₃^2-和-COO结构。覆盖度对Fe_tet1终结的表面影响很弱,但是对Fe_oct2终结的表面影响很大。从热力学上来说,CO₂在Fe_oct2终结表面的吸附要比Fe_tet1终结表面更有利。     

CO2在非质子溶剂与铁基离子液体复合体系中的吸收

选用非质子型有机溶剂聚乙二醇二甲醚(NHD)与N, N-二甲基乙酰胺(DMAC), 分别与BmimFeCl₄复配, 构建了BmimFeCl₄/NHD和BmimFeCl₄/DMAC复合铁基离子液体体系. 考察了温度、 BmimFeCl₄/溶剂的质量 比以及压力对CO₂在复合铁基离子液体体系中溶解行为的影响. 结果表明, 高压低温的吸收条件更利于CO₂ 的溶解, 当BmimFeCl₄/DMAC质量比为7∶3时, CO₂在BmimFeCl₄/DMAC复合体系中的亨利系数为0.9181 MPa·L·mol^-1, 低于同等条件下BmimFeCl₄/NHD体系的亨利系数. 在常压、 363.2 K条件下进行再生, 经5次循环后, CO₂在BmimFeCl₄/NHD和BmimFeCl₄/DMAC中的溶解度分别为初次吸收量的92.53%和99.04%. 傅里叶变换红外光谱(FTIR)结果表明, 铁基离子液体复配体系吸收CO₂为物理吸收过程. 密度泛函理论(DFT)计算与IRI分析的结果表明, 在复配DMAC的体系中, CO₂更倾向与阳离子和溶剂分子作用, 而在复配NHD的体系中, CO₂则更容易与阴离子和溶剂分子作用.     

CO2甲烷化反应路径的研究进展

CO₂甲烷化反应是一个复杂的多相催化过程,在反应过程中会产生各种各样的中间体,其反应路径目前还存在许多争议和矛盾。深入系统地研究CO₂甲烷化反应中催化剂表面中间体的演变过程,可以进一步从机理的角度优化催化剂的设计方案,提高催化性能。本工作主要基于原位红外光谱表征技术,总结梳理了最近关于CO₂甲烷化反应路径研究的相关工作,着重探讨了负载型催化剂的活性金属、载体、助剂、合成方法等因素对CO₂甲烷化反应路径的影响以及由此对催化剂性能所产生的积极效果。同时针对现阶段所面临的争论点,即反应气CO₂与H2的活化位点、催化剂的活性位点以及未来可行的研究方法进行了详细论述。     

CO2化学吸收剂

化学吸收法是燃后CO₂捕集的主要方法之一,本文介绍了化学吸收法脱除CO₂的系统工艺及特点,综述了CO₂吸收剂的研究现状,介绍了典型吸收剂:氨水吸收剂、氨基酸盐吸收剂、碳酸钾吸收剂的研究进展,以及新型吸收剂研究方向:混合胺吸收剂、相变吸收剂、离子液体吸收剂、纳米流体吸收剂,CO₂开关型吸收剂和新型有机胺吸收剂,并分析比较了各种吸收剂的优缺点。分析表明混合胺和相变吸收剂节能潜力较大,较其他四种新型吸收剂更为成熟,因此具有一定的工业化潜力。     

非胺类CO2吸收剂的研究进展

针对CO₂所带来的全球气候变化问题,本文综述了可用于捕集CO₂的非胺类吸收剂类型,认为氨基酸盐、氨基酸-碳酸钾体系、离子液体、生物型吸收剂、钙基吸收剂分别具有较高的CO₂循环吸收负荷、低毒性、热稳定性好、较优的生物相容性、钙源易获取的优势,可以弥补胺类吸收剂在吸收-解吸CO₂时腐蚀性强、再生能耗高、对环境产生二次污染等方面的不足。氨基酸盐、氨基酸-碳酸钾体系可应用于具有一定规模的CO₂捕集工业中;离子液体可应用于精准、绿色环保去除CO₂工业中;生物型吸收剂可用于规模小、CO₂浓度低的工业中;钙基吸收剂可运用于CO₂浓度高的工业中。上述吸收剂皆具有一定的工业前景。     

CO2在Cu/ZnO/Al2O3型低变催化剂上的TPD研究

本文采用程序升温脱附(TPD)法研究了CO₂在Cu/ZnO/Al₂O₃型低变催化剂上的吸、脱附行为。结果表明:在350℃以内,该催化剂对于CO₂显示出一种能量分布的活泼部位,且其主要是由催化剂中的游离ZnO所提供。以T_f法结合脱附速率等温线法进行了TPD谱图的定量解析,求出了脱附动力学参数,并发现Cu/ZnO/Al₂O₃对CO₂的有效表面为非理想表面,CO₂在Cu/ZnO/Al₂O₃上的脱附近似地服从一级过程。最后针对得到的Arrhenius图进行了有关的讨论。     

Modified Electrodes and Electrochemical Systems Switchable by Temperature Changes

This article is an overview of extensive research efforts in the area of temperature‐controlled electrochemical systems. Electrochemical reactions, including electrocatalytic and bioelectrocatalytic processes, have been reversibly activated and inhibited by temperature changes. This was achieved by modification of electrode surfaces with thermo‐sensitive polymers (e.g., poly(N‐isopropylacrylamide), PNIPAM) which are reversibly switched by temperature changes between two different structures: swollen expanded coil conformation and shrunken collapsed globule state. While the swollen hydrophilic state allows penetration of redox species to the electrode conducting support and activates electrochemical reactions, the collapsed hydrophobic state isolates the electrode surface and inhibits electrochemical processes. Electrodes modified with the thermo‐switchable polymers have been additionally functionalized with photo‐switchable molecules (e.g., spiropyran derivatives) to achieve double‐controlled electrochemical reactions switchable by temperature changes and light signals. Incorporation of metallic nanoparticles or graphene species in the temperature‐sensitive polymer films resulted in sophisticated features and multi‐signal controlled behavior of the nano‐composite systems.     

Modified Electrodes and Electrochemical Systems Switchable by Light Signals

This article is an overview of extensive research efforts in many laboratories in the last two decades in the area of light‐switchable electrochemical systems and modified electrodes. Electrochemical reactions, including electrocatalytic and bioelectrocatalytic processes, have been reversibly activated and inhibited upon irradiation with light at different wavelengths. In order to realize these light activated or inhibited processes, the electrodes or/and reacting molecules were functionalized with photoisomerizable molecules including various derivatives of diarylethene, phenoxynaphthacenequinone, azobenzene and spiropyran/merocyanine. Photochemical reactions of these species resulted in change of their redox activity, conformation and electrical charge. All these changes affected electrode surfaces or (bio)molecules resulting in switching ON‐OFF corresponding (bio)electrochemical processes. Various systems based on different light‐controlled reactions are reviewed and discussed with specific examples and with many illustrating figures. Possible extensions of the research area and future applications are briefly overviewed in the conclusion section. The present comprehensive review is addressed to a broad scientific community, including newcomers to the area.     

Spiropyran‐Conjugated Pluronic as a Dual Responsive Colorimetric Detector

Novel spiropyran‐conjugated Pluronic [polyethylene oxide (PEO)‐b‐polypropylene oxide (PPO)‐b‐polyethylene oxide (PEO)] micelles are developed as a new colorimetric detector showing photo‐ or thermo‐switchable behavior. Facile conjugation of spiropyran to Pluronic was confirmed by ¹H NMR, UV–Vis, and Fluorescence spectroscopy. A switchable photoluminescence is found depending on the irradiation with either UV or visible light, and temperature resulting from structural isomerization of spiropyran between spiropyran (SP) and merocyanine (MC) form. Cytotoxicity of the spiropyran‐conjugated Pluronic (SP‐PL) was evaluated following an MTT assay, whereas photo responsiveness of spiropyran within the micelles was determined by confocal laser scanning microscopy.     

Coaxially bifocal liquid crystal lens with switchable optical aperture

An electrically tunable liquid crystal (LC) lens with dual hole-patterned electrodes is demonstrated. When the LC lens is operated at low voltages, the dual hole-patterned electrodes with different diameters impart the lens with a coaxial bifocal characteristic. At high voltages, the proposed LC lens functions as a conventional lens with a single focal length but with a switchable optical aperture. The demonstrated LC lens is free of disclination lines because of the presence of voltage-assisted high pretilt angles created from the upmost hole-patterned electrode with small diameter.     

Synthesis and properties of double-chain single-head acetamidinium bicarbonate switchable surfactants

A series of switchable surfactants with double hydrophobic chains and a single hydrophilic head N,N’-dialkylacetamidinium bicarbonate with an alkyl length between diC8 and diC12 were synthesized by using new approaches. The structures of acetamidinium bicarbonate were characterized by ^1?H NMR and ESI-MS spectroscopy. The surface activity in aqueous solution of N,N’-dialkylacetamidinium bicarbonate and N’-alkyl-N,N-dimethylacetamidinium were compared by surface tension methods. Some surface activity parameters were studied, such as cmc, γ_cmc, pC₂₀, cmc/C₂₀, Γ_max, and A_min. The results indicated that double-chain surfactant was superior to single-chain surfactant and showed more excellent surface activity. The switchability was confirmed by monitoring the conductivity of a solution of amidine in ethanol and their effect in emulsion stability was also investigated.     

Combination of ultrasound‐assisted ethyl chloroformate derivatization and switchable solvent liquid‐phase microextraction for the sensitive determination of l‐methionine in human plasma by GC–MS

A green and fast analytical method for the determination of l ‐methionine in human plasma is presented in this study. Preconcentration of the analyte was carried out by switchable solvent liquid phase microextraction after ethyl chloroformate derivatization reaction. Instrumental detection of the analyte was performed by means of gas chromatography–mass spectrometry. N,N‐Dimethyl benzylamine was used in the synthesis of switchable solvent. Protonated N,N‐dimethyl benzylamine volume, volume/concentration of sodium hydroxide, and vortex period were meticulously fixed to their optimum values. Besides, ethyl chloroformate, pyridine, and ethanol volumes were optimized in order to get high derivatization yield. After the optimization studies, limit of detection and quantitation values were attained as 3.30 and 11.0 ng/g, respectively, by the developed switchable solvent liquid phase microextraction gas chromatography–mass spectrometry method that corresponding to 76.7‐folds enhancement in detection power of the gas chromatography–mass spectrometry system. Applicability and accuracy of the switchable solvent liquid phase microextraction–gas chromatography–mass spectrometry method were also checked by spiking experiments. Percent recovery results were ranged from 97.8 to 100.5% showing that human plasma samples could be analyzed for its l ‐methionine level by the proposed method.     

A Chiral Thermochromic Ferroelastic with Seven Physical Channel Switches

Switchable materials play an invaluable role in signal processing and encryption of smart devices. The development of multifunctional materials that exhibit switching characteristics in multiple physical channels has attracted widespread attention. Now, two chiral thermochromic ferroelastic crystals (S‐CTA)₂CuCl₄ and (R‐CTA)₂CuCl₄ (CTA=3‐chloro‐2‐hydroxypropyltrimethylammonium) have been prepared with switchable properties in dielectricity, conductivity, second harmonic generation (SHG), piezoelectricity, ferroelasticity, chiral, and thermochromic properties. Compared with traditional phase‐transition materials with switching features, thermochromism brings additional spectral encryption possibilities for future information processing. To the best of our knowledge, this is the first chiral thermochromic ferroelastic that exhibits switching properties in seven physical channels. This work is expected to promote further exploration of multifunctional molecular switchable materials.     

Switching Friction with Thermal‐ Responsive Gels

The thermosensitive graphene oxide (GO)/poly(N‐isopropyl acrylamide) (pNIPAM) composite hydrogels are prepared, and their tribological properties in response to external stimuli are evaluated. The frictional coefficient of the hydrogels is closely related to the gel composition and ambient temperature. When the gel is in swelling state below the low critical solution temperature (LCST), it shows ultra‐low friction and exhibits high friction at a shrunk state above the LCST. The huge difference of frictional coefficient under two states can be reversibly switched many times by altering the temperature. The incorporation of a nonthermal sensitive monomer into pNIPAM could change the LCST and thus the transformation point of frictional coefficient can be altered. These reversible and tunable frictional hydrogels have potential application in the design of intelligent control equipment.