共聚焦拉曼光谱研究过饱和硝酸铵液滴中NH4+, NO3- 和H2O之间的相互作用

将硝酸铵液滴沉积在石英基底上,通过降低该液滴周围环境的相对湿度,测定了该液滴由低浓度直至过饱和状态下高信噪比的拉曼光谱.其中,相对湿度的变化可以精确控制液滴浓度的改变.在相对湿度(RH)由72.1%降低至37.9%的过程中,硝酸铵液滴v1-NO-3峰位保持在1048cm-1,半峰宽为10cm-1.该现象表明NO-3周围的水分子被NH4+取代后不会对v1-NO-3造成影响,说明水分子和NH4+所形成的氢键具有相同的强度.对2500-4000cm-1范围内的拉曼光谱进行成分分析,2890、3090、3140、3220、3402及3507cm-1分别被指认为NH+4伞状弯曲振动的泛频、NH+4伞状弯曲振动与摇摆振动的组合谱带、NH+4的对称伸缩振动、NH+4的反对称伸缩振动、水峰中强氢键成分和弱氢键成分.从拟合结果得出:强氢键在氢键结构中所占百分含量随液滴相对湿度的降低而减少,弱氢键所占百分含量随液滴相对湿度的降低而增加.该变化趋势是NO-3和NH+4之间复杂相互作用的结果.     

生物滤池中生物膜和出水悬浮物的元素分析和红外光谱比较

对生物滤池中不同高度的生物膜和出水悬浮物的碳氢氮三元素和红外光谱进行了分析比较.元素分析结果表明,悬浮物的无机成份比生物膜高.悬浮物和生物膜的红外吸收光谱图主要由蛋白质的吸收带、碳水化合物的吸收带组成.1655 cm-1处的吸收峰为酰胺Ⅰ带,是C=O的伸缩振动,1542 cm-1的吸收峰是酰胺Ⅱ带,是N-H的弯曲振动和C-N的伸缩振动,1240 cm-1是酰胺Ⅲ带,是C-N的伸缩振动和N-H的弯曲振动引起的.1460 cm-1处的吸收峰为CH3和CH2的弯曲振动峰.悬浮物的蛋白质特征峰强度比生物膜低,而1050cm-1处的吸收峰强度比生物膜大.     

二维红外光谱研究聚碳酸酯薄膜中水的扩散

利用二维衰减全反射红外光谱方法,研究了水在聚碳酸酯(PC)薄膜中的扩散过程,发现水的羟基弯曲振动谱带中可以分辨出分别位于1672、1646和1621 cm-1的吸收峰,而羟基伸缩振动谱带中可以分辨出分别位于3560、3425和3255 cm-1的吸收峰,由此可知水分子在聚碳酸酯薄膜中存在3种状态,分别为与羰基形成强、中强氢键作用的水分子和进入PC微孔中的弱氢键作用的水分子。 经过二维相关分析得到水分子进入PC薄膜的顺序为首先形成中等强度的氢键,然后形成弱和强2种强度的氢键。     

含氮杂冠醚双亲聚合物纳米球的制备及性能

设计、合成了含氮杂冠醚和腺嘌呤的双亲聚合物,聚[N,N-二乙氧基-1,10-二氮杂-18冠-6-5-甲基-腺嘌呤-异酞酸酯](PCASE).SEM观测到在水溶液中该聚合物与5-氟尿嘧啶(5-flu)小分子识别后自发聚集成直径约140～210nm的纳米球,用动态光散射测得水溶液中PCASE/5-flu纳米球的粒径主要集中在120～230nm范围内,FTIR研究了PCASE/5-flu纳米球内聚合物PCASE中腺嘌呤与底物5-氟尿嘧啶的分子识别,结果表明,识别后5-氟尿嘧啶环上C(2)=O伸缩振动峰从1724cm-1位移至1718cm-1,且聚合物中腺嘌呤NH2峰3324cm-1消失,出现了一个新的NH2峰3432cm-1,说明5-氟尿嘧啶环上C(2)=O与聚合物PCASE中腺嘌呤上NH2间形成了氢键.变温红外谱显示,识别后的羰基峰1718cm-1随温度的升高逐渐向高波数回移,并最终稳定在5-氟尿嘧啶环上C(2)=O识别前的1724cm-1处,且识别后产生的新NH2峰3432cm-1随温度的升高逐渐减弱至消失,表明所形成的氢键断裂.     

N_2O分子C~1Π态的吸收光谱及解离动力学

通过四波混频差频的方法产生高分辨的真空紫外激光,用以测量143.6至146.9 nm范围内的射流冷却N2O分子吸收光谱,对应于C1Π←X1Σ+的吸收跃迁.谱图显示出三个分立的振动谱峰叠加在宽吸收背景上,谱峰间隔分别是521和482 cm-1.前人的高精度量子化学计算表明C1Π态在N—O键长方向表现为无势垒的排斥态,而在N—N键伸缩及N2O弯曲振动方向则表现为束缚态,因此观测到的振动谱峰被归属为激发态的Feshbach共振.通过反Fourier变换可以得到Feshbach共振对应的非稳定周期轨道的特征周期为61 fs,相应的振动频率为546 cm-1.鉴于这一频率与弯曲振动频率非常接近,非稳定周期轨道被认为是由C1Π态的弯曲振动与解离运动相互作用而形成的,N—N伸缩振动没有参与形成非稳定周期轨道.由此,N2O分子C1Π态光激发-解离过程得以清晰地阐述.     

化学亚胺化程度对正性光敏聚酰亚胺影响

选用2,2′-双三氟甲基-4,4′-联苯二胺(TFDB)与二苯醚四甲酸二酐(ODPA)作为聚合物的基本骨架进行缩聚反应生成聚酰胺酸,再经过化学亚胺化得到可溶性聚酰亚胺(PI)。通过调节2-甲基吡啶在亚胺化试剂中的含量以达到控制酰亚胺化程度的目的,探讨不同亚胺化程度的PI胶的显影性能。结果表明,当n(2-甲基吡啶)∶n(乙酸酐)=1∶5时,所合成的光敏聚酰亚胺的显影性能最优。     

原位红外光谱法研究电纺聚酰胺酸纳米纤维膜热亚胺化过程

以均苯二酐和二苯醚二胺为原料合成聚酰胺酸溶液,通过静电纺丝法制得聚酰胺酸纳米纤维膜.利用原位红外技术研究亚胺化进程,并以优化的条件制得聚酰亚胺纳米纤维膜.研究结果表明,当升温速率为2℃/min时,在350℃可实现100%亚胺化;升温速率过快,纳米纤维膜的亚胺化程度较低;采用快速-慢速相结合的升温方法,则可以有效地提高亚胺化效率.     

BaF2/La2O3催化剂上甲烷氧化偶联反应活性氧物种的原位红外光谱

用原位红外光谱研究了BaF2/La2O3催化剂上甲烷氧化偶联反应的活性氧物种.结果表明,催化剂经O2预吸附后,在1 108~1 118 cm-1处出现超氧物种O2-的O-O键伸缩振动峰.经18O2同位素交换实验后,原1 108~1 118 cm-1处谱峰的强度减弱,同时在1 086和1 051 cm-1处出现(O18O)-物种和18O2-物种的吸收峰.同位素交换实验进一步确证了1 108~1 118cm-1处谱峰确为O2-物种的吸收峰.在700℃下,O2-物种能够活化CH4生成C2H4,而且O2-物种的消耗量和C2H4的生成量呈很好的消长对应关系.超氧物种O2-是BaF2/La2O3催化剂上甲烷氧化偶联反应的活性氧物种.     

喷雾干燥法制备水分散聚酰亚胺

利用喷雾干燥法制备了具有良好水分散性的聚酰胺酸微纳米颗粒, 其初次分散浓度可达20%, 并具有良好的再分散性. 这种微纳米颗粒经过处理后可进一步亚胺化形成透明的聚酰亚胺薄膜, 红外光谱和热失重测试结果表明薄膜已经完全亚胺化, 说明这种微纳米颗粒可应用于制备聚酰亚胺水性涂料. 同时, 对影响产物形貌的几种因素进行了初步研究.     

聚酰亚胺LB膜研究：Ⅱ.聚酰胺酸N,N—二甲基十八铵盐LB膜的表征 …

聚酰胺酸Ｎ,Ｎ－二甲基十八铵盐ＬＢ膜具有严格排列的周期结构,其亚胺化可以在比聚酰胺酸更为温和的条件下进行。测定了沉积在单晶硅片上的聚酰亚胺涂膜的热分解性能。于真空和高温下聚酰亚胺ＬＢ膜会热解并与基片硅反应而生成规则结构的ＳｉＣ准单晶膜。     

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.     

In situ infrared spectroscopy study on imidization reaction and imidization-induced refractive index and thickness variations in microscale thin films of a poly(amic ester)

Poly(amic ester) (PAE) is a soluble precursor of polyimide that has attracted interest from both the microelectronic and the flat-panel display industries because of its several important advantages, including excellent solubility, high hydrolytic stability, and solvent-free film formation, over the polyimide precursor, poly(amic acid), for which monomer-polymer equilibration always occurs in solution due to its carboxylic acid groups. In this study, poly(3,4'-oxydiphenylene pyromellitamic diethyl ester) (PMDA-3,4'-ODA PAE) was chosen as a PAE precursor, and its thermal imidization behavior in microscale thin films was investigated quantitatively for the first time using time-resolved infrared (IR) spectroscopy. In addition, the variations of the film refractive index and thickness with temperature and time were determined in detail from the time-resolved IR spectra and are fully interpreted in this paper by considering the imidization kinetics of the precursor.     

顺丁烯二酸酐封端的新颖聚酰亚胺的合成及其结构性能研究Ⅰ．酰胺酸的合成及亚胺化动力学研究

报道合顺丁烯二酸酐基团的二苯甲酮四羧酸二酐双对氨基二苯醚酰胺酸（ＭＰＷ）的合成．该产物可用来制备具有优良性能的新颖聚酰亚胺。产物结构通过红外光谱、元素分析等进行表征。本文建立了用单谱ＤＳＣ法研究酰胺酸亚胺化动力学的新方法。结果表明其亚胺化反应级数ｎ＝３，在亚胺化过程中反应活化能及频率因子不随亚胺化程度增加而变化，数值亦保持不变。     

Controlled formation of optically reflective and electrically conductive silvered surfaces on polyimide film via a direct ion-exchange self-metallization technique using silver ammonia complex cation as the precursor

Double-surface-silvered polyimide films have been successfully fabricated using silver ammonia complex cation ([Ag(NH3)2]+) as the silver precursor and 3,3',4,4'-benzophenonetetracarboxylic dianhydride/4,4'-oxidianile- (BTDA/ODA-) based poly(amic acid) (PAA) as the polyimide precursor via a direct ion-exchange self-metallization technique. The process has been clarified to involve the loading of silver(I) into PAA via ion exchange, the thermally induced reduction of silver(I) to silver(0) and the concomitant imidization of PAA to polyimide upon thermal treatment, the subsequent silver-catalyzed and oxygen-assisted decomposition of the polyimide overlayer, and the self-accelerated aggregation of silver clusters on the film surface to produce well-defined surface silver layers. By employing [Ag(NH3)2]+ solution with a concentration of only 0.01 M and an ion-exchange time of no more than 10 min, the controlled formation of highly reflective and conductive silver surfaces upon thermal treatment at 300 degrees C for less than 4.5 h indicates that the present work provides an efficient route and an effacious silver species for polyimide surface metallization. Although the alkaline characteristics of [Ag(NH3)2]+ have a strong hydrolysis effect on the polyimide precursor chains, the final metallized films retain the key mechanical and thermal properties of the pure polyimide. Films were characterized by ATR-FTIR, XPS, ICP-AES, SEM, TEM, DSC, TGA, reflectivity, conductivity, and mechanical measurements.     

Kinetic study of low‐temperature imidization of poly(amic acid)s and preparation of colorless,transparent polyimide films

Conventional synthesis of polyimides includes high‐temperature (160–350 °C) imidization of poly(amic acid)s. In the present work, imidization has been carried out at much lower temperatures (40–160 °C). 1,2,4,5,‐cyclohexanetetracarboxylic dianhydride (HPMDA) or pyromellitic dianhydride (PMDA) was polymerized with an aromatic diamine, 4,4′‐diaminodiphenylmethane (DDPM), to give poly(amic acid)s, which were then imidized chemically. Imidization was more than 90% complete even at the very low imidization temperature of 40 °C. It was found that the imidization occurs in two steps: an initial rapid cyclization and a subsequent slower cyclization. The activation energy for the rapid process was determined to be 4.3 kJ/mol, and that of the slower process, 4.8 kJ/mol. As the imidization temperature decreases, the transmittance of the resulting polyimides tends to gradually increase, the cutoff wavelength decreases and the color becomes pale. A partially aliphatic polyimide based on HPMDA and DDPM prepared at 40 °C yielded thin films that were highly transparent and colorless, and had good flexibility, solubility and thermal stability. The polyimide films prepared in this study may be good candidates for flexible, transparent plastic substrates in the display industry. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1593–1602     

Structure and properties of a photosensitive polyimide: Effect of photosensitive group

The photosensitive poly(p-phenylene biphenylteracarboximide) (BPDA-PDA) precursor was synthesized by attaching photocross-linkable 2-(dimethylamino)ethyl methacrylate (DMAEM) monomer to its poly(amic acid) through acid/base complexation. The polyimide thin films were prepared by a conventional cast/softbake/thermal imidization process from the photosensitive precursors with various concentrations of DMAEM. The structure and properties of the polyimide films were investigated by small-angle and wide-angle x-ray scattering, refractive indices and birefringence analysis, residual stress and relaxation analysis, stress-strain analysis, and dynamic mechanical thermal analysis. In comparison with the polyimide film from the poly(amic acid), the films, which were imidized from the photosensitive precursors, exhibited a better molecular order and microstructure; however, they exhibited less molecular orientation in the film plane. Despite the enhancement in both the molecular order and microstructure, the film properties (i.e., mechanical properties, thermal expansion, residual stress, optical properties, dielectric constant, and water sorption) degraded overall due to both the decrease in molecular in-plane orientation and the formation of microvoids caused by the bulky photosensitive group during thermal imidization. That is, on one hand, the PSPI precursor formation provides an advantageous, direct patternability to the BPDA-PDA precursor, and on the other hand, it results in degraded properties to the resulting polyimide film. © 1995 John Wiley & Sons, Inc.     

Preparation and characterization of polyimide/mesoporous silica hybrid nanocomposites based on water-soluble poly(amic acid) ammonium salt

Recently, mesoporous silica was blended with polyimide to develop low dielectric constant (k) materials with improving mechanical and thermal properties of polyimide by utilizing both the nanoporous structure and silica framework. However, even the use of mesoporous silica did not show a significant decrease of k due to the phase segregation in between polyimide and the mesoporous silica materials. In this work, we attempted to prepare polyimide/mesoporous silica hybrid nanocomposites having relatively good phase mixing behavior by utilizing polyimide synthesized from a water soluble poly(amic acid) ammonium salt, which lead to low k up to 2.45. The thermal properties of polyimide were improved by adding mesoporous silicas. For this work, we have fabricated mesoporous silicas through surfactant-templated condensation of tetraethyl orthosilicate (TEOS). Pyromellitic dianhydride (PMDA)-4,4′-oxydianiline (ODA) polyimide was prepared from poly(amic acid) ammonium salt, which had been obtained by incorporating triethylamine (TEA) into PMDA-ODA poly(amic acid) in dimethylacetamide (DMAc), followed by thermal imidization.     

The effect of film thickness on the depth‐wise chain orientation of rod‐shaped polyimide

Controlling the chain orientation of polyimide is important because it affects the physical and electrical properties of the film. When a polyimide film is thick, the chain orientation has an inhomogeneous distribution along the thickness direction. In this study, poly(amic acids), the precursor of polyimide, with different coating thicknesses are dried, and the distribution of chain orientation in the thickness direction is investigated by measuring the residual solvent content with Raman spectroscopy. The effect of film thickness on the imidization rate is also studied by measuring the depth‐wise degree of imidization at the curing step. With the final cured polyimide film, the depth‐wise chain orientation is quantified by introducing the Fraser distribution function using polarized Raman spectroscopy. The thicker film has a lower degree of in‐plane orientation of polyimide chains, particularly near the substrate. This distribution of polyimide chain orientation in the thickness direction is similar to that of poly(amic acid) after drying. Fast imidization with higher solvent content for thick polyimide retards the formation of a well‐ordered structure with a high degree of in‐plane orientation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 848–857     

Poly(ether‐imide) and related sepiolite nanocomposites: investigation of physical,thermal, and mechanical properties

Novel poly(ether‐imide) and sepiolite nanocomposites were synthesized based on a unique diamine monomer with the aim of improving physical and mechanical properties of final polyimide films. The diamine was polycondensed with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride to produce related poly(ether amic acid) prepolymer. Pure poly(ether‐imide) and nanocomposite films were prepared via thermal imidization process of poly(ether amic acid). Coexistence of ether, pyridine, and phenylene functional groups in the diamine chemical structure resulted in flexible polyimide films with significant thermal, physical, and mechanical properties. Thermal stability, glass‐transition temperature, dimensional stability, and tensile properties of polymer and nanocomposites were studied and compared. Morphology of nanocomposites was also investigated using scanning and transmission electron microscopic methods to study the distribution and dispersion behavior of sepiolite nanofibers in the polyimide matrix. By introduction of sepiolite nanoparticles, overall improvement of properties was observed in respect to pure polyimides. Copyright © 2015 John Wiley & Sons, Ltd.     

Surface structure of semicrystalline polyimide films

The surface structure of thin films based on poly[4,4′-bis(4″-N-phenoxy)diphenyl]amic acid of 1,3-bis(3′,4-dicarboxyphenoxy)benzene and the product of its thermal imidization—a semicrystalline polyimide—poly[4,4′-bis(4″-N-phenoxy)diphenyl]imide of 1,3-bis(3′,4-dicarboxyphenoxy)benzene—at various stges of thermal imidization and after melting and subsequent annealing has been studied by methods of transmission, scanning electron, and atomic force microscopies. The topological structure of the film surface has been described in terms of the discrete cluster model. Under heating to 200 and 280°C, a continuous network of the infinite cluster appears; subsequent annealing leads to disintegration of the network to discrete fragments that practically correspond to clusters in the starting poly(amic acid) film. The polyimide film heated to 280°C crystallizes in the form of needle crystals stable to the argon plasma. The surface morphology of polyimide films recrystallized from melt is of the spherulite character.