改性聚偏氟乙烯接枝磺化聚(苯乙烯-co-丙烯酸)膜的研制

以过氧化苯甲酰(BPO)作引发剂,通过溶液接枝聚合法把苯乙烯/丙烯酸同时接枝到原硅酸钠改性的聚偏氟乙烯(PVDF)膜上,磺化后得到聚偏氟乙烯接枝磺化聚(苯乙烯-co-丙烯酸)膜(PVDF-g-P(SSA-co-AA)).研究了苯乙烯和丙烯酸的不同比例对膜的接枝反应及其相对湿度对膜电导率和含水量的影响.用傅立叶变换红外光谱(FTIR)检测原硅酸钠改性的PVDF膜经过接枝和磺化后所发生的结构变化,并用扫描电镜(SEM)观察PVDF膜接枝前后的形貌以及接枝磺化后产物PVDF-g-P(SSA-co-AA)膜的形貌及硫和硅分布.结果表明,原硅酸钠改性的PVDF膜与苯乙烯/丙烯酸同时发生接枝聚合反应,环境的相对湿度在20%～80%范围,对添加10wt%Na4SiO4的PVDF-g-P(SSA-co-AA)膜的电导率的影响基本不变,并达到0.0198S·cm-1.原硅酸钠改性的PVDF膜结构在接枝前后和磺化前后发生变化,确认磺化反应不只是在膜表面,同时渗入膜中进行.     

分子水平研究不同嵌段结构苯乙烯/丁二烯共聚物的表面结构

利用具有准单分子层灵敏度的和频振动光谱(SFG)、原子力显微镜(AFM)和接触角(CA)测定技术研究链结构和溶剂对苯乙烯(S)/丁二烯(B)嵌段共聚物表面准分子层化学结构形成的影响.结果表明,两嵌段共聚物SB比三嵌段共聚物SBS更有利于聚丁二烯(PB)组分在膜表面富集.利用PB的选择性溶剂环己烷做溶剂时,SB膜表面层完全由纯的PB组分组成,而SBS表面则是聚苯乙烯(PS)与PB二组分共存.利用PS的选择性溶剂甲苯做溶剂时,SB与SBS表面都是PS与PB二组分共存,其中SBS表面PS组分的含量更高.原因是由于溶剂影响嵌段共聚物分子在溶液中的构象从而影响溶剂挥发后聚合物表面结构的形成.     

新型磺化聚酰亚胺膜的合成与表征

合成了4,4’-二(间氨基苯氧基)联苯-3,3’-二磺酸(mBAPBDS)单体, 采用红外光谱和核磁共振等方法对其结构进行了表征. 使用mBAPBDS, 2-(对胺基苯基)苯并噁唑-5-胺(APBA)和1,4,5,8-萘四甲酸二酐(NTDA)共聚合成了含有噁唑结构的新型磺化聚酰亚胺(NTDA-mBAPBDS/APBA), 通过控制磺化二胺与非磺化二胺的比例来控制磺化程度. NTDA-mBAPBDS/APBA共聚物表现出较好的溶解性、成膜性能和良好的热稳定性, 其磺酸基团分解温度高于300 ℃. 采用溶液浇铸法制备了磺化聚酰亚胺(SPIs)膜, 对膜的吸水率、溶胀度和质子电导率等性能进行了初步的研究. 结果表明, SPIs膜具有适当的吸水率和良好的尺寸稳定性, 其室温电导率在4.72×10－3和9.60×10－3 S/cm之间, 接近于相同条件下Nafion®117的电导率(9.80×10－3 S/cm).     

SEBS/PMMA共混物膜的表面和本体形态结构

用扫描电镜(SEM)和原子力显微镜(AFM)研究了两种不同共混比的聚(苯乙烯-嵌-乙烯/丁烯-嵌-苯乙烯)(SEBS)和聚甲基丙烯酸甲酯(PMMA)共混膜的表面形态和相分离行为。结果表明,当膜厚为25μm时,两种共混膜表面均未见明显的相分离形貌,而在膜体相中可见宏观相分离结构。当膜厚为120 nm时,质量比为30/70的共混膜表面可见明显的“海-岛”状宏观相分离;而质量比为60/40的共混膜表面未见明显宏观相分离,仅有少量PMMA小颗粒嵌于SEBS基体中,形成SEBS趋于包裹PMMA微区的稳定“笼型”结构,其尺度属于介观相分离。退火后,两样品膜的体相形态与表面形貌趋于一致,均呈现宏观的相分离结构。     

用于燃料电池的磺化聚芳醚砜质子交换膜材料的直接合成与性能研究

将磺化二氯二苯砜(SDCDPS)、二氯二苯砜(DCDPS)与4,4′-联苯酚(BP)通过亲核缩聚反应得到一系列具有不同磺化度的磺化聚芳醚砜(SPAES)共聚物.通过FT-IR,TGA和DSC等分析方法对其结构及性能进行表征.并用透射电镜对其内部形态进行分析,建立了结构与性能之间的关系.研究了不同磺化度对膜性能的影响.结果表明,聚合物中磺酸基团的增多导致了磺化聚芳醚砜膜的吸水率、离子交换容量、质子传导率和甲醇渗透系数的增加.通过对膜的综合性能评价发现,磺化度为0.8的磺化聚芳醚砜膜在80℃时的质子传导率为0.116S/cm,100℃时的质子传导率为0.126S/cm,均高于Nafion117膜(0.114S/cm和0.117S/cm),且甲醇渗透系数为8.4×10-7cm2/s,远远低于Nafion117膜(2.1×10-6cm2/s).     

苯乙烯在阴离子型聚氨酯纳米水分散液中聚合过程的研究

采用自乳化法制备出阴离子聚氨酯纳米水分散液,以其作为乳化剂使苯乙烯单体在其中进行聚合,制备出不同聚苯乙烯与聚氨酯质量比的阴离子型PS/PU纳米复合物水分散液;对苯乙烯单体的聚合过程进行了研究;采用光子相关谱仪和透射电镜对其微观结构、粒径及其分布进行了测试,结果表明,该方法能够制备出稳定的具有核壳结构的PS/PU纳米复合物水分散液,但当苯乙烯单体浓度增大到一定程度(PS/PU质量比为50∶100)时,粒子不稳定而发生聚集.     

聚苯乙烯/层状双金属氢氧化物纳米复合材料的制备与表征

由离子交换法制备4,4′-偶氮二(4-氰基戊酸)根(ACP)单独插层和ACP/对苯乙烯磺酸根(VBS)复合插层的层状双金属氢氧化物(LDH),再通过原位悬浮聚合制得聚苯乙烯(PS)/LDH纳米复合材料,对插层改性LDH和复合材料进行了结构和性能表征.X-射线衍射和元素分析表明ACP可以单独或与VBS一起插入到LDH层间.透射电镜和X-射线衍射分析表明采用ACP/VBS复合插层LDH与苯乙烯原位聚合得到的复合材料中LDH剥离程度高,熔融加工后LDH基本以纳米层板形式分散在PS基体中.LDH的引入可明显提高PS的热稳定性,而熔体流动性下降.     

四甲基氢氧化铵改性聚偏氟乙烯接枝苯乙烯磺化膜的制备和性能

使用四甲基氢氧化铵(TMAH)甲醇溶液在液相中改性聚偏氟乙烯(PVDF),挥发溶剂得到改性聚偏氟乙烯膜(g-PVDF-M),再以过氧化苯甲酰(BPO)为引发剂,将苯乙烯接枝到g-PVDF-M膜中,磺化后制得改性聚偏氟乙烯接枝苯乙烯磺化(PVDF-g-PSSA)膜.利用傅里叶变换红外光谱(FTIR)和能谱仪的扫描电子显微镜分析了PVDF-g-PSSA膜(TMAH-25)的结构、形貌及硫元素分布情况.通过电化学工作站和气相色谱仪研究了TMAH在甲醇中的不同含量对PVDF-g-PSSA膜质子电导率和甲醇渗透率的影响.结果表明,TMAH使PVDF脱去HF生成碳碳双键,并且苯乙烯接枝到改性的聚偏氟乙烯膜中,磺化后S元素在PVDF-g-PSSA膜内部均匀分布;PVDF-g-PSSA膜的质子电导率和甲醇渗透率随TMAH在甲醇溶液中质量分数的增加而增大;TMAH的质量分数为25%时,PVDF-g-PSSA膜的电导率达1.28×10~(-2)S/cm,甲醇渗透率为4.58×10~(-7)cm~2/s.热重分析(TGA)表明,PVDF-g-PSSA膜的热稳性良好,耐热温度高达195℃,PVDF-g-PSSA膜作为电解质材料的直接甲醇燃料单电池(DMFC)功率密度达到16.45 mW/cm~2.     

大环化合物改性聚苯乙烯纳米纤维膜对染料吸附性能的研究

通过静电纺丝的方法制备吡啶酮大环化合物改性聚苯乙烯纳米纤维膜(PS/PBPM纳米纤维膜)用于水溶液中染料的去除。PS/PBPM纳米纤维膜的结构和表面形貌通过红外光谱和扫描电镜进行了表征。结果表明,改性后的纤维表面变得粗糙,比表面积相应增大;吸附过程符合准二级动力学模型和Langmuir等温吸附模型;该吸附剂对孔雀石绿具有很好的选择性,最大吸附容量能达到466.02mg/g;PS/PBPM纳米纤维膜的吸附性能在酸性条件下可恢复,具有良好的重复使用性能。     

层状共连续PA6/SEBS体系的结晶取向及其低膨胀化机理研究

研究了注射成型尼龙6/苯乙烯-乙烯/丁烯-苯乙烯嵌段共聚物(PA6/SEBS)体系中微结构形态,SEBS含量,PA6结晶取向对线膨胀系数(CLTE)的影响.研究表明,当SEBS含量超过20wt%,PA6/SEBS注射成型体系形成层状共连续结构时,可以明显地降低流动方向的热膨胀系数.TEM和WAXD分析表明,该层状共连续结构中不仅SEBS微层取向,而且大多数PA6片晶垂直于SEBS微层生长,其中晶胞b轴(PA6分子链)倾向于沿流动方向取向.程序升温WAXD研究表明,PA6/SEBS(60/40)体系中各晶轴的线膨胀系数差别很大,其中晶胞b轴为-5.8×10-5K-1.具有负膨胀系数的晶胞b轴沿着流动方向取向可能是除层状共连续结构效应以外导致材料低膨胀化的第二种驱动力.     

Studies of the solution properties of sulfonated-(styrene-(ethyrene-CO-butylene)-styrene) block copolymer

The dilute solution properties of lightly sulfonated hydrogenated styrene-butadiene-styrene block copolymer (S-SEBS) dissolved in tetrahydrofunan (THF) were studied by viscometry. The ring conformation in dilute regime can be deduced from the intrinsic viscosity data. It is believed that this special conformation results from the location of ionic group at both two-end blocks. The intermolecular aggregation can be observed when the solutions undergo the freezing–thawing process in the same concentration region. The extent of aggregation is affected by the freezing–thawing cycle times, water content in THF, and the counterion radii, etc. The properties of the aggregation equilibrium are also discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2677–2681, 1998     

Langmuir monolayer and Langmuir–Blodgett films of amphiphilic triblock copolymers with water-soluble middle block

Langmuir monolayers and Langmuir–Blodgett (LB) film morphology of amphiphilic triblock copolymers are studied using surface pressure-area measurements and atomic force microscopy (AFM), respectively. The triblock copolymers are composed of long water-soluble poly(ethylene oxide) (PEO) chains as middle block with very short poly(perfluorohexylethyl methacrylate) (PFMA) end blocks. The surface pressure-area isotherms show phase transitions in the brush regime. This phase transition is due to a rearrangement of PFMA block at the air–water interface. It becomes more significant with increasing PFMA content in the copolymer. LB films transferred at low surface pressures from the air–water interface to hydrophilic silicon substrates show surface micelles in the size range of 50–100 nm. A typical crystalline morphology of the corresponding PEO homopolymer is observed in LB films of copolymers with very short PFMA blocks, transferred in the brush region at high surface pressure. This crystallization is hindered with increasing PFMA content in the copolymer.     

聚苯乙烯-聚(4-乙烯基吡啶)嵌段共聚物LB膜结构形态的研究

采用氯仿作为铺展溶剂,将嵌段共聚物聚苯乙烯-聚(4-乙烯基吡啶)(PS-b-P4VP)稀溶液铺展于空气与水界面上,利用Langmuir-Blodgett(LB)膜技术转移至固体基底.研究了不同的嵌段比、表面压和小分子1-芘丁酸(PBA)的加入对嵌段共聚物气液界面聚集组装的影响.研究发现随着亲水段(P4VP)的增加,聚集组装结构由纳米片状、带状转变成纳米条状、纳米点状结构.表面压对纯PS-b-P4VP聚集组装产生影响,表面压增大,组装体排列紧密;随着表面压的继续增大,单层聚集结构遭到破坏,发生堆叠.加入PBA小分子后,PBA与PS-b-P4VP形成氢键,形态发生明显变化,原来的片状结构转变为条状或点状结构.     

Structures of palmitoyl-L and DL-lysine monolayers at the air-water interface--polarization modulation infrared reflection absorption spectroscopic study

Polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) was applied to measure the IR spectra of palmitoyl-DL-lysine (L-PL) and palmitoyl-DL-lysine (DL-PL) at the air-water interface. The spectra in the amide I and II regions were simulated by using the extinction coefficients of the amide I and II bands of L-PL and DL-PL determined by the analyses of the IR external reflection spectra of the Langmuir-Blodget (LB) films prepared on a Ge plate (Yasukawa et al. J. Mol. Struct. 2005, 735-736, 53), indicating the angle between the plane of the secondary amide group (the amide plane) and the surface normal in the L-PL monolayer to be about 20 degrees and the angle in the DL-PL monolayer to be about 37 degrees. Comparison of the tilt angles with the corresponding angles in the LB films (about 20 degrees for the LB film of L-PL; about 49 degrees for the LB film of DL-PL) indicated that, upon being transferred to the solid substrate from the air-water interface, the L-PL monolayer keeps the orientation of the amide plane virtually unchanged, while the DL-PL monolayer changes the orientation appreciably to a horizontal direction. The orientation change of the amide plane was interpreted as due to the accommodation of irregularly oriented palmitoyl groups into the LB films of DL-PL on the solid substrate.     

Formation, structure, and morphology of triazole-based Langmuir-Blodgett films

The formation, morphology, and structure of two-dimensional Langmuir-Blodgett (LB) assemblies of octadecyltriazole (ODT)-based metal-containing oligomers presenting, in the case of iron, the spin-crossover phenomenon is studied with Brewster angle microscopy, IR dichroism, X-ray diffraction, and atomic force microscopy. Two processes occurring at the air-water interface are confirmed to dominate the mechanism of formation of these LB films, the instability of the coordination polymers at the air-water interface and recoordination of metal ions in the subphase at the interface during the LB deposition process. The Langmuir film allowing the LB film formation is mostly made of ODT. The films do present a lamellar structure in which the ODT molecules are tilted and incorporate coordinated isolated metal ions and oligomers of metal ions. The morphology of the LB films is globally flat but with a rather high roughness resulting from inhomogeneities related to phenomena occurring during the LB film formation. These observations are in agreement with the relative affinity of the metal ions with ODT and the relative stability of the coordination polymers at the air-water interface, which have been determined for the group Cu-Fe-Co-Ni.     

甲基丙烯酸—磷脂酰乙醇甲基丙烯酰胺共聚物LB膜的研究

制备了不同摩尔比的甲基丙烯酸-磷脂酰乙醇甲基丙烯酰胺共聚物,研究了这种共聚物在水面的表面压力(π)-分子面积(A)曲线、共聚物制成的MOS LB膜的电容(C)-电压(V)特性及此LB膜的相变温度。     

Surface chemistry studies of (CdSe)ZnS quantum dots at the air-water interface

Trioctylphosphine oxide- (TOPO-) capped (CdSe)ZnS quantum dots (QDs) were prepared through a stepwise synthesis. The surface chemistry behavior of the QDs at the air-water interface was carefully examined by various physical measurements. The surface pressure-area isotherm of the Langmuir film of the QDs gave an average diameter of 4.4 nm, which matched very well with the value determined by transmission electron microscopy (TEM) measurements if the thickness of the TOPO cap was counted. The stability of the Langmuir film of the QDs was tested by two different methods, compression/decompression cycling and kinetic measurements, both of which indicated that TOPO-capped (CdSe)ZnS QDs can form stable Langmuir films at the air-water interface. Epifluorescence microscopy revealed the two-dimensional aggregation of the QDs in Langmuir films during the early stage of the compression process. However, at high surface pressures, the Langmuir film of QDs was more homogeneous and was capable of being deposited on a hydrophobic quartz slide by the Langmuir-Blodgett (LB) film technique. Photoluminescence (PL) spectroscopy was utilized to characterize the LB films. The PL intensity of the LB film of QDs at the first emission maximum was found to increase linearly with increasing number of layers deposited onto the hydrophobic quartz slide, which implied a homogeneous deposition of the Langmuir film of QDs at surface pressures greater than 20 mN.m(-1).     

Fabrication of densely packed titania nanosheet films on solid surface by use of Langmuir-Blodgett deposition method without amphiphilic additives

Densely packed exfoliated nanosheet films such as Ti0.91O2, Ti0.8M0.2O2 (M = Co, Ni), Ti0.6Fe0.4O2, and Ca2Nb3O10 on solid substrates were prepared by the LB transfer method without any amphiphilic additives at the air-water interface. Nanosheet crystallites covered nearly 95% on the solid surface with minimum overlapping of nanosheets. The LB transfer method of the Ti0.91O2 nanosheet monolayer film is applicable for not only hydrophilic substrates such as quartz, silicon, indium-tin oxide (ITO), and glass but also the hydrophobic Au surface. On the basis of these points, the LB transfer method has advantages compared to the alternating layer-by-layer method, which makes use of oppositely charged polyelectrolytes such as poly(ethylenimine) (PEI). Adsorption of hydrophobic Ti0.91O2 nanosheets at the air-water interface is responsible for this LB transfer deposition method. The addition of tetrabutylammonium bromide into the subphase assisted the adsorption, causing an increase in the adsorbed amount of Ti0.91O2 nanosheets at the air-water interface.     

Polymer-surfactant layered heterostructures by electropolymerization of phenosafranine in Langmuir-Blodgett films

Langmuir-Blodgett (LB) films of the water-soluble dye phenosafranine (PS) have been prepared by its adsorption from aqueous dye solution to an arachidic acid (AA) monolayer at the air-water interface. Atomic force microscopy (AFM) images of the LB films revealed the effect of change in pH of deposition on the degree of complexation of AA with the PS dye. Well-defined circular islands and holes were observed which disappeared with the increase in pH. Polarized absorption studies indicated that the dye molecules are oriented uniaxially with their long axis titled at a constant angle to the surface normal of the LB film. Within the restricted geometry of the LB film, the PS dye was electropolymerized to form a two-dimensional film of poly(phenosafranine) sandwiched between arachidic acid layers. The film was characterized by IR spectroscopy, cyclic voltammetry, and AFM. X-ray diffraction studies reveal the presence of a layer structure in the AA-PS LB film before and after polymerization. The polymer film showed highly anisotropic electrical conductivity of ca. 10 orders of magnitude. This indicates the formation of two-dimensional polyPS layers between arachidic acid layers resulting in a layered heterostructure film having alternate conducting and insulating regions. Also, the conductivity of the polyPS prepared from LB film was found to be approximately 2.5 times higher than the conductivity of polyPS prepared by solution polymerization method.     

Effect of water and air-water interface on the structural modification of Ni-arachidate Langmuir-Blodgett films

Nickel arachidate (NiA) Langmuir-Blodgett (LB) films have been deposited on hydrophilic Si(0 0 1) substrates by three (up-down-up) and five (up-down-up-down-up) strokes. During deposition, substrates were kept inside the water subphase for different times after each down stroke. Structural information of all the LB films have been obtained from X-ray reflectivity (XRR) studies. One and two symmetric monolayer (SML) was deposited on top of the asymmetric monolayer (AML) in three and five stokes respectively. All the preformed LB films were then used to go through the air-water interface with the same speed that was used at the time of film deposition. Structural information obtained from the XRR studies show that mainly the top layer density decreases after passing through the air-water interface but the layered structure remains the same. Information obtained from both the XRR and atomic force microscopy (AFM) studies suggest that molecules peeled from the top SML layer do not reincorporate with the LB film through tail-tail hydrophobic interaction. Our study shows that NiA LB film has better stability compared with cadmium arachidate LB film inside the water subphase without forming any out-of-plane molecular reorganization.