聚合物Langmuir—Blodgett膜研究进展

聚合物LB膜可用两种方法制备,一种是两亲单体成膜再进行聚合反应,另一种为直接从两亲聚合物在亚相表面铺展成膜并转移。本文综合聚合物LB膜的研究状况,包括两亲聚合物和非两亲聚合物,对聚合物LB膜的成膜特点,结构和性能作了描述,并简要介绍了聚合物LB膜的应用前景。     

聚合物的LB膜

简要介绍了聚合物LB(Langmuir -Blodgett)膜的制备装置和制备过程。同时对聚合物LB膜这一门学科最新的进展和应用前景做了较为详尽的介绍和论述。目前 ,随着对LB膜的研究深入 ,在对小分子LB膜、可聚合LB膜、聚合物LB膜的成膜研究中引入了将几种方法优点综合起来的新的成膜方法 ,并已成为研究热点     

导电聚合物超薄膜的制备及性能表征

采用修饰LB膜法制备了导电聚合物聚-3,4-乙烯二氧噻吩/硬脂酸(PEDOT/SA)复合超薄膜. 将硬脂酸(SA)/FeCl3 LB膜暴露于EDOT单体气氛中, EDOT 单体在多层膜中聚合, 制备了PEDOT/SA多层复合LB膜. 紫外-可见光-近红外(UV-Vis-NIR)吸收光谱和X射线光电子能谱(XPS)分析表明EDOT单体在多层膜中发生聚合并生成PEDOT导电聚合物. 扫描电子显微镜(SEM)分析显示生成的PEDOT导电聚合物颗粒分散于硬脂酸LB膜中, 被LB 膜所包裹. 二次离子质谱(SIMS)及XPS分析还发现S元素含量随LB 膜的深度变化而变化, 表明PEDOT 较好地分散于多层膜中. 采用四探针电导率仪对复合多层膜的电导率进行了测试, 结果显示60 层复合LB 膜的电导率为2.6 S·cm-1, 比普通PEDOT薄膜的电导率高一个数量级, 且表现出较好的掺杂/脱掺杂能力. 研究还发现复合膜电导率与薄膜在EDOT 单体中处理时间有关, 处理时间至120 min 后电导率达到最大值并趋于稳定, 氧化剂浓度较低可能影响EDOT在LB膜中的聚合反应速率. 对复合LB 膜的气敏特性进行了分析, 发现在较低气体浓度范围(φ<30×10^-6), PEDOT 复合LB 膜有较快的反应速率, 气敏性与气体浓度呈非线性. 在较高浓度范围(φ=(30-120)×10^-6), 气敏性与浓度呈较好的线性关系. PEDOT复合LB膜对HCl气体表现出较好的响应恢复特性. 同时对PEDOT 复合膜相关的导电机理及气体敏感机理进行了分析.     

柔性间隔基对于香豆素取代二乙炔LB膜聚合及手性形成的影响

设计合成了2种香豆素取代二乙炔单体,7-(10,12-二十三双炔酰氧基)-香豆素(CODA)和7-(10,12-二十三双炔酰氧乙氧基)-香豆素(CO2DA),研究了柔性间隔基对香豆素取代二乙炔单体在气-液界面的组装、单体LB膜的聚合以及聚二乙炔主链螺旋结构形成的影响.利用Langmui-Blodgett(LB)技术,以纯水为亚相,膜压在35 mN/m时沉积制备了香豆素取代二乙炔单体LB膜.尽管CODA是非手性的,但其LB膜均表现出明显的宏观手性信号.这是由于在压缩过程中香豆素基团间强烈的π-π堆积,形成了螺旋排列,显示出超分子手性.而CO2DA LB膜无明显CD信号.经254 nm紫外光辐照,CODA LB膜聚合成蓝相,聚二乙炔主链表现出明显的宏观手性.而CO2DA LB膜聚合后无明显的CD信号.薄膜中香豆素功能基团的不规则排列不利于二乙炔单体的固态聚合以及聚二乙炔主链螺旋结构的形成.     

辐射接枝法制备离子交换膜的研究现状

聚合物离子交换膜有多种制备方法，其中高分子材料辐射引发接枝功能性单体是一种文献中屡见报道且简单可行的方法．通过在不同聚合物基体上接枝各种类型的单体，可以改变接枝膜的电化学性能、物理化学等性能．丈中详细介绍了不同的高分子基材辐射接枝各类单体制备聚合物离子交换膜的研究现状．     

修饰Langmuir-Blodget膜法制备聚(3,4-亚乙基二氧噻吩)薄膜结构和导电性能的研究

采用修饰Langmuir-Blodget(LB)膜法以二十烷酸(AA)LB膜为模板,通过3,4-亚乙基二氧噻吩(EDOT)单体在LB膜亲水基团间聚合,制备了二十烷酸/聚(3,4-亚乙基二氧噻吩)(AA/PEDOT)复合LB膜.UV-Vis、FTIR和XPS分析表明EDOT在多层膜中有效聚合,生成了PEDOT导电聚合物;X射线衍射(XRD)和二次离子质谱(SIMS)分析表明薄膜具有较好的层状有序结构,进一步研究发现EDOT在AA多层膜中的聚合破坏了原有LB膜的有序性,这可能与聚合过程对层状结构产生的破坏作用有关;采用四探针仪及半导体测试仪研究了薄膜导电性能,发现AA/PEDOT多层膜的电导率随处理时间的变化产生突变,这与多层膜中导电通道的"逾渗"有关,在有效导电网络连通后电导率发生了突变.测试结果还表明AA层和PEDOT层之间具有较为明显的界面,PEDOT显示出较好的定域性,薄膜具有很好的层状有序结构.     

氟哌酸分子印迹共混膜的制备及结构表征

以氟哌酸为模板分子,α-甲基丙烯酸为功能单体,三甲氧基丙烷三甲基丙烯酸酯为交联剂,利用本体聚合方法制备了具有特异选择性的氟哌酸分子印迹聚合物,并利用聚砜与氟哌酸分子印迹聚合物共混的方法制备了分子印迹聚合物膜.运用红外光谱分析和透射电子显微镜研究了氟哌酸分子印迹聚合物的结构.运用扫描电子显微镜研究了分子识别膜的机理和吸附性能,运用平衡结合实验法证明了分子识别膜对氟哌酸表现出了较高的选择性.     

二价钌有机螯合物Ru(dpphen)2+3与花生酸混合LB膜的结构及光谱特性

对不同组分的Ru(dpphen)2+3［简称Ru(Ⅱ)］与花生酸(AA)在纯水亚相上的混合单分子膜的相容性、分子间相互作用以及凝聚单分子膜的结构进行了研究. 成功地将这种功能单体分子膜转移到固体载片上,制备成混合LB膜. 紫外-可见光谱、发射光谱及小角X光衍射表明这种混合LB膜是一种稳定、均一、具有良好的层状结构, 并且在可见光范围内具有很强的吸收及发射峰的功能膜.     

邻香草醛分子印迹聚合物膜的制备及其透过选择性质的研究

采用紫外光引发原位聚合的方法制备了具有支撑膜的邻香草醛分子印迹聚合物膜. 紫外光度法测定了模板分子和功能单体之间的结合常数和化学计量比(n＝2). 用傅立叶红外光谱和扫描电镜分别测定了膜的结构和表面形貌; 膜渗透实验结果表明在干扰物存在时印迹膜对模板分子表现出良好的选择透过性能. 研究了分子印迹聚合物膜透过的机理、并为分子印迹技术应用于传感器领域增加了理论和实验方法.     

二价钌有机螯合物Ru（dpphen）3^2＋与花生酸混合LB膜的结构及光谱特性

对不同组分的Ru(dpphen)3^2 [简称Ru(Ⅱ）]与花生酸（AA）在纯水来相上的混合单分子膜的相容性、分子间相互作用以及凝聚单分子膜的结构进行了研究,成功地将这种功能单体分子膜转移到固体载片上,制备成混合LB膜、紫外－可见光谱、发现光谱及小角X光笛射表明这种混合LB膜是一种稳定、均一、具有良好的层状结构,并且可在可见江范围内具有很强的吸收及发射峰的功能膜。     

Synthesis and Investigation of Monoesters of Polymaleic Acids with Azo Group

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Preparation, properties, and reactions of metal-containing heterocycles: Part CVI. Three-dimensional water-soluble platinacyclophanes

Trifunctional primary phosphines of the type 1,3,5-[PH₂(CH₂)_n]₃C₆H₃ (3b–d) were obtained via an Arbusov reaction between the 1,3,5-tris(bromoalkyl)benzenes 1b–d and P(OEt)₃ followed by a reaction of the trisphosphonates 1,3,5-[(EtO)₂P(O)(CH₂)_n]₃C₆H₃ (2b–d) with LiAlH₄. A straightforward conversion of these sensitive key phosphines 3b–d to the corresponding water-soluble ligands 1,3,5-tris[bis(hydroxymethyl)phosphinylalkyl]benzenes 4b–d and 1,3,5-tris[bis(2′-diethylphosphonatoethyl)phophinylalkyl]benzenes 5b–d was achieved by formylation with formaldehyde and hydrophosphonation with diethyl vinylphosphonate, respectively. A five component self-assembly consisting of three equivalents of the platinum(II) complex Cl₂Pt(NCPh)₂ and two equivalents of the ligands 5b–d under high dilution conditions resulted in the formation of the nanoscaled, water-soluble triplatinacyclophanes 6b–d in high yields. However, comparable reactions with the ligands 4b–d led only to polymeric materials, which are insoluble in all organic solvents and water. The structures of the metallacyclophanes 6b–d were elucidated by ³¹P{¹H}-, ¹³C{¹H}-, and ¹⁹⁵Pt{¹H}-NMR spectroscopic investigations.     

Characterization and decomposition mechanism of an unusual nickel, thiocyanate and 4-methylpyridine polymeric complex

The synthesis, characterization, and thermal decomposition of the [Ni(SCN)₂(H⁺SCN)₂(4-mepy)₂] compound with an octahedral structure in polymeric chain were reported, in which SCN groups form bridges among Ni(II) ions. The compound decomposes in water resulting in a pH<4 solution. The FT-IR spectrum presented doublet bands at 2117; 2128 cm⁻¹, 788; 773 cm⁻¹ assigned to ν(C---N) and ν(C---S) stretching modes, respectively, and δ(SCN) deformation modes at 468; 476 cm⁻¹. The Raman spectrum of the compound presented the ν(C---N) stretching as a strong doublet at 2122; 2128 cm⁻¹, ν(C---S) at 783; 770 cm⁻¹, and δ(SCN) at 468; 477 cm⁻¹. No significant changes were observed in the 4-mepy ligand bands compared with the vibrational frequencies of the pure compound or the compound in aqueous solution 0.2 mol l⁻¹. The crystal UV–vis reflectance spectrum presented two bands centered in 626 and 424 nm tentatively assigned to the d→d type transitions, ³A_2g→³T_1g and ³A_2g→³T_1g, for a symmetry close to O_h. The TG curve showed a mass loss between 120 and 200 °C assigned to the loss of the two 4-mepy molecules; from 200 to 265 °C, the loss of the two H⁺SCN groups; and from 265 to 450 °C, the loss of the two SCN groups that formed the bridges among the nickel atoms. Based on these mass loss data, a mechanism of thermal decomposition for the compound was proposed.     

Dissociation reactions of the vinyl radical in the AA″ state

In the present theoretical work we have explored mechanisms of dissociation reactions of the vinyl radical in the A²A″ state (C₂H₃ (A²A″)) and examined possible pathways for nonadiabatic dissociation of C₂H₃ (A²A″) into C₂H₂ (X¹Σ_g⁺). In the calculations we used the complete active space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) methods in conjunction with the cc-pVDZ and cc-pVTZ basis sets. Mechanisms for the following three dissociation channels of C₂H₃ in the A²A″ state were explored: (1) C₂H₃ (A²A″) → C₂H₂ (trans, ³A_u) + H, (2) C₂H₃ (A²A″) → C₂H₂ (cis, ³A₂) + H, and (3) C₂H₃ (A²A″) → H₂CC (³A₂) + H. The CASSCF and CASPT2 potential energy curve calculations for the C₂H₃ (A²A″) dissociation channels (1)–(3) indicate that there is neither transition state nor intermediate for each of the channels. At the CASPT2//CASSCF/cc-pVTZ level, the dissociation energies for channels (1)–(3) are predicted to be 84.3, 91.1, and 86.9 kcal/mol, respectively. For a recently observed nonadiabatic dissociation of C₂H₃ (A²A″) into C₂H₂ (X¹Σ_g⁺) + H [J. Chem. Phys. 111 (1999) 3783], two previously suggested internal conversion (IC) pathways were examined based on our CASSCF and CASPT2 calculations. Our preliminary CASSCF and CASPT2 calculations indicate that the assumed IC pathway via the twisted C₂H₃ (A²A^′) structure might be feasible. The CASSCF/cc-pVTZ geometry optimization and frequency analysis calculations were performed for the four C_2v bridge structures in the ²B₂, ²A₂, ²B₁, and ²A₁ states along the pathways of the 1²A^′ (X²A^′), 1²A″ (A²A″), 2²A″, and 2²A^′ states of C₂H₃, respectively, and the CASPT2//CASSCF/cc-pVTZ energetic results indicate that the assumed IC pathway, via a C_2v (²A₂) structure and then ²A₂/²A₁ surface crossing, be not feasible since at their excitation wavelengths (327.4 and 366.2 nm) the C_2v (²A₂) structure could not be accessed.     

部分还原二氧化钛的NMR和EPR研究

Partially reduced TiO₂ nanomaterials have attracted significant interest because of their visible-light activity for catalysis and photodegradation. Herein, we prepared a partially reduced anatase TiO₂ (Re-A-TiO₂) nanoparticle material using a fast combustion method, demonstrating good activity toward decomposing methyl orange under visible light irradiation. The surface structure of the prepared material, after being surface-selectively ¹⁷O-labeled with H₂¹⁷O (¹⁷O-enriched water), was studied via ¹⁷O and ¹H solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and electron paramagnetic resonance (EPR) spectroscopy, and the obtained results were compared to those of non-reduced anatase TiO₂ (A-TiO₂). The EPR results showed that the concentrations of paramagnetic species (i.e., oxygen vacancies (OV) and Ti³⁺) in Re-A-TiO₂ were much higher than that in A-TiO₂, while the former was associated with a higher OV/Ti³⁺ ratio. The intensities of the EPR signals were significantly affected by the adsorbed water, and this phenomenon was explored in combination with ¹H NMR spectroscopy. The ¹H species on Re-A-TiO₂ appeared at larger chemical shifts, denoting the increased acidity of the sample, and these ¹H species on Re-A-TiO₂ were more difficult to remove than those on A-TiO₂. On the other hand, different features were observed for the signals arising from the two-coordinated oxygen atoms (μ₂-O) in ¹⁷O NMR, suggesting a typical anatase TiO₂(101) surface on A-TiO₂, but a more complex surface environment for Re-A-TiO₂. Furthermore, a larger amount of hydroxyl groups (OH) were observed on Re-A-TiO₂ compared to that on A-TiO₂, indicating a larger proportion of exposed (001) facets on Re-A-TiO₂. However, the μ₂-O signals broadened and became similar when the drying temperature was increased to 100 ℃, indicating a non-faceted anatase TiO₂ surface in such conditions. Based on the EPR and NMR results, a significant fraction of the OH species is believed to be formed from the reaction of the paramagnetic centers and adsorbed water molecules. The ¹H→¹⁷O cross polarization (CP) MAS and two-dimensional heteronuclear correlation (2D HETCOR) NMR spectra were used to verify the spatial proximity of the hydrogen and oxygen species, confirming the spectral assignments of a strongly adsorbed water and one type of surface OH species. In particular, the ¹H NMR signals at approximately 11 ppm were ascribed to the hydrogen species in the intramolecular hydrogen bond. In summary, this study investigated the paramagnetic species and surface structure of anatase TiO₂ materials by combining EPR along with ¹H and ¹⁷O solid-state NMR spectroscopy. The differences in the surface structures of Re-A-TiO₂ and A-TiO₂ should be closely related to their different properties toward the photodegradation of methyl orange.     

Fraction of excited-state oxygen formed as b Σg in solution-phase-photosensitized reactions II. Effects of sensitizer substituent

The fraction F_Σ of excited-state oxygen formed as b ¹Σ_g⁺ was determined for a series of triplet-state photosensitizers in CCl₄ solutions. F_Σ was determined by monitoring the intensities of (a) O₂(b ¹Σ_g⁺) fluorescence at 1926 nm (O₂(b ¹Σ_g⁺)→O₂(a ¹Δ_g) and (b) O₂(a ¹ Δ_g) phosphorescence at 1270 nm (O₂(a ¹Δ_g) → O₂(X³Σ_g⁻)). Oxygen excited states were formed by energy transfer from substituted benzophenones and acetophenones. The data indicate that F_Σ depends on several variables including the orbital configuration of the lowest triplet state and the triplet-state energy. The available data indicate that the sensitizer-oxygen charge transfer (CT) state is not likely to influence F_Σ strongly by CT-mediated mixing of various sensitizer-oxygen states.     

Pyrrole studies part 41. Reactivity of 3,4-diformyl-2,5-dimethylpyrrole with diaminoalkanes. An unusual formation of 2-azafulvenes

3,4-Diformyl-2,5-dimethylpyrrole (1) reacts with ,ω-diamino-alkanes, NH₂(CH₂)_nNH₂t' to form either the potentially tautomeric 2:2 macrocyclic adduct (7a) (8), when N = 2, or the potentially tautomeric 1:1 bicyclic adduct (18) (19), when N = 4, 5, 6, and 12. ¹H and ¹³C N.m.r. spectral data indicate that the 2-azafulvene structures predominate for both types of cycloadducts. Only polymeric material was obtained when N = 3.     

Reactivity and electronic property of decaphenylmetallocenes of Mo and W atoms

The perphenylmetallocene complexes (η⁵-C₅Ph₅)₂W (1), [(η⁵-C₅Ph₅)₂W]⁺I₃⁻ (1⁺I₃), (η⁵-C₅Ph₅)₂Mo (2) and [(η⁵-C₅Ph₅)₂Mo]⁺I₃⁻ (2⁺I₃) have been prepared. Hydrogenation of 1 in THF produces (η⁵-C₅Ph₅)₂WH₂ (4), while (η⁵-C₅Ph₅)₂WHCl (3) is afforded in 1,2-dichloroethane solvent. Carbonylation of 1 produces (η⁵-C₅Ph₅)₂W(CO) (5). Treatment of 1 with the strong acid CF₃SO₃H leads to the dicationic species [(η⁵-C₅Ph₅)₂W]⁺²[CF₃SO₃]⁻₂ (1⁺²Tf₂) after crystallization. The structures of 2⁺I₃ and 1⁺²Tf₂ have been determined by an X-ray diffraction study. The magnetic susceptibility study indicates a ³E_2g ground-state for 1 and 2, and a ⁴A_2g ground-state for 1⁺ and 2⁺.     

Ab initio study of the electronic spectrum of dichlorocarbene CCl2

The equilibrium geometries, excitation energies, force constants and vibrational frequencies for seven low-lying electronic states X ¹A₁, ¹B₁, ³B₁, ¹A₂, ³A₂, ¹B₂ and ³B₂ of dichlorocarbene CCl₂ have been calculated at the MRSDCI level with a double-zeta plus polarization basis set. Our calculated equilibrium geometry for the X ¹A₁ state, excitation energy for X ¹A₁ → ¹B₁ and vibrational frequencies for the X ¹A₁ and ¹B₁ states are in good agreement with experimental data. The electronic transition dipole moments, oscillator strengths for the ¹B₁ → X ¹A₁ and ¹B₂ → X ¹A₁ transitions, radiative lifetimes for the ¹B₁ and ¹B₁ states are calculated using MRSDCI wavefunctions, predicting results in reasonable agreement with experiment.     

Ab initio molecular orbital study of potential energy surface for the H2NO(B1)→NO(Π)+H2 reaction

The mechanism of the H₂NO(²B₁)→NO(²Π)+H₂ reaction has been examined using ab initio molecular orbital methods. Ground-state and first-excited-state potential surfaces were plotted at the FOCI/cc-pVTZ level of theory as functions of two appropriate internal degrees of freedom. A conical intersection was found on the C_s pathway that is symmetric with respect to the plane perpendicular to the molecular plane of C_2v H₂NO(²B₁). It is therefore considered that trajectories that start from H₂NO(²B₁) towards the product region detour around the conical intersection, pass through the neighborhood of the transition state that is located at the saddle point on the C_s pathway, and finally reach the products, NO(²Π)+H₂. Thus we can explain the mechanism of the H₂NO(²B₁)→NO(²Π)+H₂ reaction, which has remained unclear to date.