超临界二氧化碳制备聚合物微孔膜的研究进展

超临界二氧化碳做非溶剂制备聚合物微孔膜是一个新的研究热点,具有传质系数高、聚合物膜干燥速度快且不破坏结构、溶剂容易回收、CO2可循环使用、CO2的低毒性与环境友好性等特点.本文介绍采用超临界CO2制备聚合物微孔膜的热力学及动力学原理,重点介绍近年来采用此技术制备微孔膜的研究成果,如以聚苯乙烯（PS）、聚丙烯腈（PAN）、聚醚砜（PES）等为基体的微孔聚合物膜.     

两亲性梳状聚醚硅氧烷对相转化法聚偏氟乙烯多孔膜的共混改性作用研究

以聚醚链段为侧链的两亲性梳状聚醚硅氧烷(ACPS)为改性剂,研究了相转化法制备聚偏氟乙烯(PVDF)多孔膜的改性效果与机理.采用SEM、XPS、接触角、水通量等考察了ACPS对膜结构与性能的影响.研究发现,ACPS在相转化成膜过程中不流失,随着制膜液中ACPS含量的增加,相分离速度降低,膜中微孔由指状结构向蜂窝状结构发展,膜强度提高,亲水性显著提高.提出了ACPS在膜表面的富集现象和在膜中的稳定性机理和模型.结果表明,两亲性梳状聚醚硅氧烷在原理上是一类适合于相转化法制备聚合物微孔膜表面亲水化改性的有效物质.     

磺化聚醚酰亚胺/聚醚酰亚胺共混膜的结构与性能

将亲水性的磺化聚醚酰亚胺(SPEI)和疏水性的聚醚酰亚胺(PEI)共混,以N,N-二甲基乙酰胺(DMAc)为溶剂,制备了SPEI(Na型)／SPEI中空纤维超滤膜．研究了纺丝过程中内凝固浴组成比例和空气间隙距离变化对膜结构以及膜分离性能的影响。实验结果表明,随着内凝固浴中DMAc含量的提高,纤维内指状孔减少,水通量下降,而截留率则不受影响;随着空气间隙距离的增大,从膜内壁侧出发的指状孔结构前端逐渐向外壁发展,而膜的外壁侧则逐渐变得致密,同时,膜的外表面可能出现较大的微孔结构,导致膜的水通量随着空气间隙距离的增加而迅速增加后随之下降,而截留率则一直保持下降趋势。     

内凝固浴组成对聚醚酰亚胺中空纤维膜结构和性能的影响

以N,N-二甲基乙酰胺(DMAc)为溶剂,水为外凝固浴,乙醇为内凝固浴,DMAc为内凝固浴添加剂,采用相转化法制备了聚醚酰亚胺(PEI)中空纤维膜,研究了内凝固浴组成和纺丝液浓度对膜结构和性能的影响。实验结果表明,随着内凝固浴中DMAc含量在一定范围内增加,纤维断面指状孔有所减少,内表面由无孔到有微孔出现,但膜的水通量下降,截留率不受影响;随着纺丝液浓度提高,膜的水通量下降,截留率提高。     

聚乙二醇对聚醚砜微孔膜致孔作用的研究

以聚醚砜聚乙二醇溶剂为铸膜液体系、采用干湿相转化法制备微孔滤膜,研究了各种制膜条件对膜孔径结构的影响.实验发现聚乙二醇在体系中起到分散稳定的作用,只有到浓度大于70%时,才会对铸膜液的粘度产生明显影响,聚合物在铸膜液中的溶解状态也随之改变,进而影响膜的结构.不同溶剂NMP、DMF、DMAc、DMSO等极性溶剂或固体溶剂己内酰胺均可制得开孔率较高的微孔膜,但对膜的结构和性能影响差别不大.在本研究体系中,膜的结构取决于聚乙二醇、溶剂的浓度比例关系.     

内凝固浴流速对聚醚酰亚胺中空纤维膜结构与性能的影响

以N,N-二甲基乙酰胺为溶剂,水为内、外凝固浴,制备聚醚酰亚胺中空纤维膜,研究了内凝固浴流速对膜的形态结构、分离性能以及力学性能的影响。实验结果表明：随着内凝固浴流速的提高,纤维外径略有下降、内径有较大程度的提高、壁厚减小,其它结构无明显变化。与此相对应,膜的力学性能有一定程度的下降,而水通量有很大程度的提高,截留率变化不大。当内凝固浴流速／纺丝液流速大于0．4时,纤维内壁表面产生较大的轴向应力,把处于相分离早期的分子链或分相微区拉开,产生了微孔。     

工艺条件对 LLDPE/POE/CaCO3微孔膜的孔结构及防水透湿性能的影响

用拉伸致孔法制备了 LLDPE/POE/CaCO3防水透湿微孔膜,研究了拉伸倍数及体系组成对微孔膜的微孔结构及防水透湿性能的影响.用 SEM 对微孔膜的微孔结构进行考察,用压汞法对微孔膜的孔径及其分布和微孔的孔隙率进行研究.用静水压法及正杯法分别研究了微孔膜的防水和透湿性能.结果表明:拉伸倍数及 CaCO3用量对微孔膜的孔径、孔隙率及防水透湿性能有明显影响.     

氟碳链封端聚醚酰亚胺改性环氧树脂的相分离研究--分子量的影响

采用差示扫描量热仪(DSC), 扫描电子显微镜(SEM)和时间分辨光散射(TRLS)研究不同分子量的氟碳链封端聚醚酰亚胺对改性环氧树脂的相分离的影响. 结果表明, 氟碳链端基的引入, 由于低表面能氟碳链封端聚醚酰亚胺的阻隔作用, 而使相分离速度降低, 相结构演变时间缩短, 固化后的相结构相间距缩小. 随着氟碳链封端聚醚酰亚胺分子量的增加, 相结构由分散相转变为双连续相. 因此可以通过改变聚醚酰亚胺的端基及分子量调控相结构.     

氟碳链封端聚醚酰亚胺改性环氧树脂的相分离研究

采用差示扫描量热仪(DSC), 扫描电子显微镜(SEM)和时间分辨光散射(TRLS)研究不同分子量的氟碳链封端聚醚酰亚胺对改性环氧树脂的相分离的影响. 结果表明, 氟碳链端基的引 入, 由于低表面能氟碳链封端聚醚酰亚胺的阻隔作用, 而使相分离速度降低, 相结构演变时间缩短, 固化后的相结构相间距缩小. 随着氟碳链封端聚醚酰亚胺分子量的增加, 相结构由分散相转变为双连续相. 因此可以通过改变聚醚酰亚胺的端基及分子量调控相结构.     

静电纺丝法制备聚醚酰亚胺纤维膜的结构和介电性能研究

采用静电纺丝法制备了聚醚酰亚胺(PEI)纤维膜,通过扫描电子显微镜(SEM)和偏振红外对PEI纤维膜的微观结构进行研究.实验结果显示纺丝液溶剂决定了PEI的可纺性,以N-甲基吡咯烷酮(NMP)为溶剂时,空气湿度显著地影响纺丝过程以及纤维的形态.在相同纺丝工艺条件下,随着纺丝液浓度的增加,所得PEI取向纤维沿辊筒收集方向的排列规整性提高,纤维平均直径由405 nm增加到3.25 μm.PEI纤维膜介电性能的研究表明,取向纤维膜的介电常数很小,最低可达到1.1,其介电损耗也维持在较低的水平,纤维膜的接收方式以及热牵伸处理会对PEI纤维膜的介电性能产生影响.     

漆酚醛胺聚合物多孔膜的制备

以漆酚醛胺聚合物(UFDP)为成膜材料,利用水辅助自组装的固体基板展开法和水面展开法制备了漆酚醛胺聚合物多孔膜.研究了在静态(即不在聚合物表面吹扫氮气)高湿度环境下聚合物溶液浓度、环境湿度和固体基板等因素对多孔膜形貌的影响.结果表明,水面展开法更有利于形成单层的多孔膜而固体基板展开法得到的是多层的多孔膜.当UFDP聚合物浓度为6.0 mg/mL,环境相对湿度为90%时,用水面展开法制得的单层多孔膜的孔径分布较均匀.     

Porous thin films based on photo-cross-linked star-shaped poly(D,L-lactide)s

Self-assembly processes and subsequent photo-cross-linking were used to generate cross-linked, ordered microporous structures on the surfaces of well defined four-arm star-shaped poly(D,L-lactide) (PDLLA) thin films. The four-arm star-shaped PDLLAs were synthesized using an ethoxylated pentaerythritol initiator. Solutions of the PDLLAs were cast in a humid environment, and upon solvent evaporation, ordered honeycomb structures (or breath figures) were obtained. Correlations between molar mass, polymer solution viscosity, and pore dimensions were established. The average pore dimension decreased with increasing polymer solution concentration, and a linear relationship was observed between relative humidity and average pore dimensions. Highly ordered microporous structures were also developed on four-arm star-shaped methacrylate-modified PDLLA (PDLLA-UM) thin films. Subsequent photo-cross-linking resulted in more stable PDLLA porous films. The photo-cross-linked films were insoluble, and the honeycomb structures were retained despite solvent exposure. Free-standing, structured PDLLA-UM thin films were obtained upon drying for 24 h. Ordered microporous films based on biocompatible and biodegradable polymers, such as PDLLA, offer potential applications in biosensing and biomedical applications.     

Facile way of dynamically tailoring microporous structures in polyvinylidene fluoride films prepared by thermally induced phase separation

Polyvinylidene fluoride (PVDF) films were prepared via thermally induced phase separation (TIPS) using diphenyl carbonate as the diluter in an attempt to disclose the competitive relationship between crystal growth and droplet growth during phase separation process. By varying the quenching temperature different temperature gradient fields were established, which were theoretically evaluated via enthalpy transformation method. The effects of polymer concentration and quenching temperature on evolution of hierarchical morphologies in TIPS films were systematically investigated. According to the morphological characteristics, the cross-sectional morphology of the films with lower polymer concentration (Φ_P = 25%) could be divided into three layers; while that of higher polymer concentration counterpart (Φ_P = 55%) only presented a bi-layered structure. The reason for this could be ascribed to the effect of cooling rate on both crystal growth and droplet growth during TIPS process, which further determined the formation of the hierarchical structure in microporous films. With an increasing quenching temperature, both pore size and porosity of PVDF films increased, accompanied by an improvement on both thermal stability and dynamic mechanical thermal property. The present study could insightfully supply a facile route to fabricate structure-controllable microporous films of crystalline polymers via an appropriate regulation of the TIPS quenching parameters.     

热诱导相分离法制备亲水性乙烯-丙烯酸共聚物微孔膜

选择 3种不同丙烯酸含量的乙烯 丙烯酸共聚物 (EAA)为原材料 ,二苯醚 (DPE)为稀释剂 ,采用热诱导相分离法 (TIPS)制备了亲水性高分子微孔膜 .接触角实验证明 ,EAA为亲水性高分子材料 .利用熔点仪根据浊度的变化测绘出 3种不同EAA/DPE体系的双结点线以及通过DSC得出相应 3体系的结晶温度曲线 .实验结果还表明 ,随着乙烯 丙烯酸共聚物中丙烯酸含量的增加 ,结晶温度曲线向低温方向移动 ,相对应的膜孔直径也增加 .此外 ,随着EAA DPE体系中EAA初始浓度的逐渐增加 ,膜孔直径逐渐变小 ,当体系中EAA初始浓度高于 5 0 %时 ,不再出现微孔结构     

Nanostructure formation in polymer thin films influenced by humidity

The influence of relative humidity (RH) during the film preparation on the surface morphology and on the material distribution of the resulting technical polymer blend films consisting of poly (methyl methacrylate) (PMMA) and poly (vinyl butyral) (PVB) is investigated by atomic force microscopy. Both pure polymers and polymer blends with different compositions of PVB/PMMA dissolved in tetrahydrofuran (THF) were used. Polymer films prepared under dry conditions (RH < 20%) are compared with those that have the same polymer composition but were prepared under increased humidity conditions (RH > 80%). The films consisting of the pure polymers showed a nonporous surface morphology for low‐humidity preparation conditions, whereas high‐humidity preparation conditions lead to porous PVB and PMMA films, respectively. These pores are explained as the result of a breath figure formation. In the case of the polymer blend films containing both polymers, porous or phase‐separated surface structures were observed even at low‐humidity conditions. A superposition of the effects of phase separation and breath figure formation is observed in the case of polymer blend films prepared under high‐humidity conditions. Atomic force microscopy (AFM) images taken before and after the treatment with ethanol as a selective solvent for PVB indicate that PMMA is deposited on top of a PVB layer in the case of the low‐humidity preparation process whereas for high‐humidity conditions the silicon substrate is covered with a PMMA film. Copyright © 2006 John Wiley & Sons, Ltd.     

Nitrate removal of drinking water by means of catalytically active membranes

The reduction of nitrate to nitrogen in aqueous solutions by means of catalytically active membranes has been investigated. A heterogeneous catalyst (Pd/Cu) has been incorporated in a microporous polyetherimide membrane. After saturation with hydrogen nitrate containing water was filtered through these membranes. The nitrate reduction was studied as a function of pH, volume flow and temperature. It could be demonstrated that the catalyst remained active in the polymer matrix. The calculated activation energy for nitrate reduction is indicating that the reaction is dominated by mass transfer and diffusion.     

Fabrication of Honeycomb-Structured Poly(DL-lactide) and Poly[(DL-lactide)-co-glycolide)] Films and their Use as Scaffolds for Osteoblast-Like Cell Culture

Summary: Surfactant-free honeycomb-structured Poly(DL lactide) (PDL LA) and Poly-(DL lactide-co-glycolide) PDL LGA thin films were fabricated by water droplet templating methods. Thin films with uniform pore structure were obtained after controlled evaporation of solvents in a humid atmosphere. Solvent, polymer concentration and humidity were found to be important factors in the formation of honeycomb-structured thin films. Preliminary cell culture studies with MG-63 osteoblast-like cell lines showed promising degrees of cell attachment and proliferation on these films, suggesting that they are applicable as scaffolds for tissue engineering.     

A novel polypropylene microporous film

The structure and properties of a polypropylene microporous film prepared by biaxial stretching of non-porous polypropylene film of high β-crystal content were investigated. The porosity of these films can be as high as 30–40%, and the average pore size was around 0.05 μm. The films were found to have the structure of a two-phase interpenetrating network; both the polypropylene and the pore regions were three-dimensionally continuous. The advantages of the biaxially stretched microporous films are the combination of high permeability to fluids with good mechanical properties and almost circular pore shape with narrow pore size distribution. The application of this microporous film for battery separators, filtration membranes and substrates of functional polymer composites is discussed.     

Phase-inversion gradient-porous films on the basis of polyamidoimides derived from phthalimidobenzenedicarbonyl dichloride and various diamines

Morphology of microporous films prepared from aromatic polyamidoimides under different molding conditions was studied by scanning, transmission, and atomic force microscopy with the specific attention given to the nanosize skin layer. The films were manufactured by the phase inversion molding of aromatic polyamidoimides which were synthesized by low-temperature polycondensation of phthalimidobenzenedicarbonyl dichloride with various diamines. Comparison of the parameters of films, including their wettability and X-ray photoelectron spectroscopy data, gave additional information on factors affecting the mechanism of formation of microporous membranes in the system polymer (polyamidoimide)-solvent (N-methylpyrrolidin-2-one)-non-solvent (water).     

甲醇气氛静态呼吸图法制备蜂窝状有序多孔膜

以原子转移自由基聚合方法合成的聚二甲基硅氧烷-b-聚苯乙烯(PDMS-b-PS)为铸膜材料,在静态呼吸图的基础上,首次在甲醇氛围下利用PDMS-b-PS的二硫化碳溶液铸膜得到了高度规整的蜂窝状有序多孔结构.研究了聚合物溶液浓度对孔径的影响,并与水蒸汽氛围制备的孔结构进行了比较.结果表明,甲醇气氛下制备的多孔膜的孔径比水蒸汽氛围下的大,且孔的断面形貌呈“U”形;孔径随着溶液浓度的增大而减小.该研究有利于呼吸图法制备有序结构材料技术的进一步发展,有助于人们更加准确与全面地认识呼吸图机理.