凝固浴温度对PVDF铸膜液相分离过程和膜结构的影响

采用皮-亚两步凝胶成膜机理探讨了凝固浴温度对PVDF铸膜液的相分离行为及其膜结构的影响.采用浊度法测定不同温度时铸膜液体系的热力学性质,光透射仪测定不同凝固浴温度时沉淀速率对膜的形态和性能的影响.结果显示:皮层的生成主要受热力学性质控制,随着凝固浴温度的提高,皮层由液固分相转变为液液分相,延时时间缩短,皮层由相互融合的球粒致密结构转变为多孔结构.亚层的生成主要受皮层结构和溶剂/非溶剂相互扩散的影响,膜亚层主要发生液液分相;随凝固浴温度升高,分相速率加快,大孔发展更充分,膜的孔隙率和气通量提高,但结晶度降低.     

添加剂对PVDF相转化过程及膜孔结构的影响

研究了PVP、PEG及LiCl 3种成孔添加剂下PVDF DMAc H2 O 添加剂体系的成膜机理 .无论那种添加剂的铸膜液相转换成膜过程中都存在凝胶分相和液液分相两种相变方式 ,在 30～ 6 0℃时凝胶分相在较低的非溶剂浓度下先于液液分相发生 ,LiCl作为添加剂较PEG、PVP对铸膜液有较强的致凝胶作用 ,成膜过程中凝胶分相段时间依PVP、PEG、LiCl的顺序延长 ,导致液液分相初始分相点处聚合物浓度增大 ,阻止了大孔结构的充分发展 .制得的膜依PVP、PEG、LiCl的顺序有效孔隙率和通量降低 ,结晶度升高 .以LiCl为添加剂制得的膜几乎不改变PVDF膜的疏水性 ,而以PVP或PEG为添加剂的膜隔水压差降低约 2 0kPa .     

扩散致相转化法制备结晶性聚合物多孔膜

介绍了扩散致相转化法制备结晶性聚合物多孔膜的研究现状。其三元等温成膜体系的相图包含液-液分相和固-液分相两种相分离方式,是理解成膜过程的重要工具,总结了成膜机理和膜的结构形貌：单纯S-L相分离生成粒子状对称膜结构;单纯L-L相分离生成蜂窝状非对称膜结构;两种相分离方式竞争发生将生成多样的混合膜结构。铸膜液浓度、非溶剂种类、铸膜溶剂组成、凝胶浴组成、制膜温度是影响膜结构形貌的主要因素。     

聚偏氟乙烯-磺化聚醚砜相容性及其成膜性能

研究了聚偏氟乙烯(PVDF)-磺化聚醚砜(SPES)的相容性及其成膜性能.首先通过溶解度参数、粘度法和目测法研究共混溶液的相容性,接着采用浊度法测定了共混溶液的热力学性质,最后采用浸没沉淀法制备了共混膜并探讨了成膜性能.结果显示,PVDF和SPES为部分相容体系,随着SPES含量的增加,共混溶液相容性逐渐减小,当SPES含量增加到50wt%时,体系发生分相.共混溶液的成膜性能良好,SPES含量增加有利于体系发生液液分相,生成高孔隙率膜,并且极大的提高了PVDF膜的亲水性和水通量.     

溶剂对PVDF铸膜液相转化和微孔膜皮-亚两层结构的不同影响

采用皮-亚分步凝固成膜机理分析了3种不同溶剂对聚偏氟乙烯(PVDF)铸膜液相转化和膜结构的影响,采用浊度法测定铸膜液体系的热力学性质,沉淀速度采用光透射仪测定.结果显示,3种膜的皮层分相主要由热力学性质控制,均发生延时液固分相,生成了相互融合的球粒组成的致密皮层.3体系的亚层分相行为由动力学扩散过程控制;对于二甲基亚砜(DMSO)、N,N-二甲基乙酰胺(DMAc)体系亚层发生瞬时液液分相,结晶化对动力学过程影响小,表现为光透射曲线上分相时间t2短,生成了大孔结构为主的亚层,膜厚度、孔隙率和气通量均高、结晶度低;N,N-二甲基甲酰胺(DMF)体系亚层发生延时液液分相,结晶化对动力学过程影响大,t2长,生成蜂窝状孔结构亚层,其膜厚度、孔隙率和气通量较低,但膜的结晶度高.     

聚偏氟乙烯/左旋聚乳酸的相容性及其共混膜的结构和性能研究

动态力学分析(DMA)、溶度参数法、聚合物混合焓法对聚偏氟乙烯(PVDF)和左旋聚乳酸(PLLA)的相容性分析结果显示,随着共混体系中PLLA的增加,PVDF和PLLA之间的相容性变差。扫描电镜(SEM)、广角X-射线衍射(WAXD)和拉伸实验对共混膜中PVDF/PLLA配比对其微观结构和力学性能影响的分析结果显示,随PLLA含量从10%增加到50%,共混膜由均匀致密结构变为存在缝隙的多孔结构,共混膜结晶度增加,断裂伸长率下降,断裂强度先增加后下降,在PLLA含量为40%时,强度达到最大。     

TEP-DMAc混合溶剂对PVDF膜性能的影响

利用非溶剂相转化法(NIPS)制备聚偏氟乙烯(PVDF)膜,考察了聚乙二醇(PEG200)与N,N-二甲基乙酰胺(DMAc)的质量比对膜分相速率和膜性能的影响,讨论了以磷酸三乙酯(TEP)和DMAc的混合液作溶剂对PVDF膜凝胶速率、膜结构和膜通量的影响。结果表明:PEG200的加入减弱了溶剂对聚合物的溶解能力,但铸膜液的分相行为由延迟分相转变为瞬时分相,膜通量提高。随着混合溶剂中TEP含量的增大,铸膜液的黏度增大,分相速率减慢;在高质量比m(TEP)/m(DMAc)时,膜表面的孔增多,指状孔膜结构逐渐消失,整个膜截面呈海绵状,膜通量变大,力学性能提高。     

聚左旋乳酸/聚氧化乙烯共混物的拉伸行为及结构转变

采用熔融共混方法制备了聚左旋乳酸(PLLA)和超高分子量聚氧化乙烯(PEO)共混物, 通过差示扫描量热(DSC)、 扫描电子显微镜(SEM)和二维广角X射线散射(2D-WAXS)等方法系统研究了PEO的加入对不同温度下PLLA拉伸行为及拉伸过程中微观结构变化的影响. 结果表明, PLLA/PEO共混物为非均相体系, PEO粒子均匀分布在PLLA中形成两相结构. PEO的加入能够显著降低PLLA的玻璃化转变温度(T_g), 在25～60 ℃范围内显著提高PLLA的拉伸性能. 在60 ℃拉伸时, PEO的加入提高了PLLA在拉伸过程中的结晶和形变能力. 在80 ℃拉伸时, 共混物的拉伸断裂伸长率下降, 但共混物的结晶速度仍高于纯PLLA样品.     

热致相分离法偏二氯乙烯-氯乙烯共聚物多孔膜的制备及性能

以偏二氯乙烯-氯乙烯共聚物[P(VDC-co-VC)]为成膜聚合物, 邻苯二甲酸二甲酯(DMP)为稀释剂, 采用热致相分离(TIPS)法制备了具有多孔结构的P(VDC-co-VC)膜. 通过聚合物-稀释剂二元体系相图、 场发射扫描电镜(FESEM)、 差示扫描量热仪(DSC)、 X射线衍射(XRD)、 原子力显微镜(AFM)、 纯水通量、 接触角、 孔径及其分布、 截留率及力学性能等研究了聚合物含量对P(VDC-co-VC)多孔膜结构和性能的影响. 结果表明, P(VDC-co-VC)-DMP二元体系成膜过程以液-液(L-L)分相为主, 随着聚合物含量增加, 膜的横截面由类花瓣状结构向胞腔状结构转变, 膜的孔连通性降低, 结构变得较为致密, 同时膜上表面孔隙率降低, 粗糙度增大. L-L分相时间和聚合物含量的变化, 导致膜结晶度先降低后增大. 聚合物含量的增加使膜上表面接触角、 断裂强度及蛋白截留率增加, 但膜的平均孔径、 孔隙率及纯水通量先增加后减小. 当聚合物质量分数为30%时, 所得膜通透性较优, 断裂强度可达7.5 MPa.     

草酸对非对称膜成膜过程中热力学、流变学和凝胶动力学的影响

以酚酞基聚芳醚砜/草酸/N,N-二甲基乙酰胺为铸膜液体系, 考察了草酸对非对称膜成膜过程中的热力学、流变学和凝胶动力学的影响. 结果表明, 草酸的加入, 在热力学上加速了铸膜液的相分离. 成膜过程中凝胶动力学的研究结果表明, 凝胶前锋位移的平方与时间不是简单的线性关系. 将凝胶过程与非对称膜的结构相对应, 分为4个连续的凝胶过程, 凝胶速度曲线由4段具有不同速度常数的线段组成. 在凝胶过程中, 凝胶速度常数最大的是皮层.     

Effect of the polarity of additional solvent on membrane formation in polysulfone/N-methyl-2-pyrrolidone/water ternary system

Asymmetric polysulfone membranes were prepared by wet phase inversion method with different demixing rate of casting solutions. The influent factor of demixing rate was focused on the polarity of additive in the polysulfone/N-methyl-2-pyrrolidone/water ternary system. With increasing the polarity of alcohols in the casting solution, the decrease in skin layer thickness was observed and then a poor separation performance of membranes can be obtained. It was found that the polar additive caused the rapidly demixing of casting solution in coagulation bath and formed porous asymmetric membranes with defective skin layer. In the other case, chloroform was used as the non-polar additive in casting solution. With increasing the mount of chloroform in the casting solution, the increase in skin layer thickness was observed and then lead to a good separation performance of these membranes. It was found that of the non-polar additive delays the demixing rate of casting solution in this ternary system. The separation performance of these asymmetric membranes were characterized by the measurement of dehydration of ethanol/water mixture by pervaporation and observed the morphology by scanning electron microscopy. It was found that the separation performance of asymmetric polysulfone membrane strongly depends on the polarity of adding solvent in polysulfone/N-methyl-2-pyrrolidone/water ternary system.     

Preparation and biodegradation of electrospun PLLA/keratin nonwoven fibrous membrane

As a kind of natural protein, wool keratin was used to improve the cell affinity of poly(l-lactic acid) (PLLA). After small keratin particles were prepared from keratin solution by spray-drying process, they were blended with PLLA solution. PLLA/keratin nonwoven fibrous membrane was produced by electrospinning the blend solutions. The release rate of keratin from the composite membrane was detected by Fourier transform infrared (FTIR) after PLLA/keratin membranes were degraded in PBS up to 4 weeks. The chemical compositions of the PLLA/keratin surface were examined by X-ray photoelectron spectroscope. Although more than half of the keratin was removed from PLLA/keratin membrane during the first few hours of degradation, some keratin particles were still embedded in the PLLA fibers. Osteoblast cells were used to evaluate the cellular behaviors of the composite membrane. After 7 days culturing, more cells were observed on PLLA/keratin membranes than on pure PLLA membranes. MTT assay and alkaline phosphatase (ALP) activity results suggested that keratin could improve the interactions between osteoblast cells and the polymeric membranes.     

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.     

Characteristics of polyethersulfone/sulfonated polyimide blend membrane for proton exchange membrane fuel cell

Solution-cast membranes from sulfonated polyimide (SPI) and its blend were prepared from polyethersulfone (PES) and SPI. The water uptake and swelling were tested and compared between the SPI membrane and the four kinds of blend membranes. Through comparison of the stability of the membranes, we concluded that the PES could greatly increase the stability of the whole membrane and restrict the swelling. However, the PES did not decrease the water uptake very much. We also compared the fuel cell performance with different membranes. The performance was decreased when the content of the PES in the blend membrane increased. The loss of the fuel cell performance with the blend membranes did not decrease very much before the content of the PES was exceeded 20%. It was prospected that the blend membrane could increase the stability of the SPI and, more importantly, even replace the commercial Nafion membranes.     

耗散粒子动力学模拟Nafion膜和PVA/Nafion共混膜的介观结构

采用耗散粒子动力学模拟方法研究了水化Nafion膜和水化聚乙烯醇(PVA)/Nafion共混膜的微结构.模拟结果表明水化Nafion膜和水化PVA/Nafion共混膜均能形成相分离的微结构.在水化Nafion膜中,水与磺酸根混合形成管状的水团簇.随着膜内水含量增多,管状水团簇的尺寸逐渐变大并在膜内形成连续的水通道.在水化PVA/Nafion共混膜中,PVA、水、磺酸根混合形成亲水性区域.共混膜中PVA的质量分数和水含量共同影响膜的微结构.当膜中PVA质量分数较低时,PVA主要分布在Nafion的磺酸根基团周围;PVA质量分数升高后,PVA会在膜内单独成一相.当膜中的水含量相对较低时,水分子会溶解于PVA中,此时膜内不存在单独的水团簇;膜中的水含量增多后,膜内会形成接近于球形的水团簇.本文工作可为直接甲醇燃料电池用的PVA改性Nafion膜的开发提供参考.     

Demixing Time and Temperature Influence on Porosity and Interconnection of PLLA Scaffolds Prepared via TIPS

Scaffolds suitable for tissue engineering applications were prepared by Thermally Induced Phase Separation (TIPS) starting from a ternary solution PLLA/dioxane/water. The experimental protocol consisted of three consecutive steps, a first quench from the homogeneous solution to an appropriate demixing temperature (within the binodal region), a liquid-liquid demixing stage for a given time and a final quench from the demixing temperature to a low temperature (within the spinodal region). A large variety of morphologies, in terms of average pore size and interconnection were obtained upon modifying the demixing time and temperature, owing to the interplay of nucleation and growth processes during the residence in the metastable state. An interesting combination of micro and macro-porosity was observed for longer demixing times (above 30 min at 35 °C).     

磺化聚芳醚砜/磺化聚酰亚胺复合质子交换膜的制备与性能研究

利用溶液浇铸法制备了一系列双磺化型磺化聚芳醚砜/磺化聚酰亚胺(SPAES/SPI)复合质子交换膜.扫描电子显微镜(SEM)结果显示复合膜不存在明显的相分离,表明二者具有很好的相容性.由于SPI的引入,复合膜在甲醇中稳定性较纯SPAES具有大幅的提高,比Nafion112低得多的甲醇吸收率表明了这些复合膜具有比后者更低的甲醇透过率.复合膜显示了与单组分膜相类似的高温分解稳定性,磺酸基团的分解温度达到了290℃以上.复合膜显示出远高于纯SPAES膜的尺寸稳定性能,在130℃高温中200h处理后,所有的复合膜均保持了高的机械性能,而此时纯SPAES膜已经溶解于水中.而且由于两种磺化聚合物间的复合,复合膜维持了较高的IEC水平,显示了较高的质子导电率,在80%相对湿度时的质子导电率与Nafion112相近,而在水中的质子导电率均高于Nafion112.     

Preparation and characterization O-lauroyl chitosan/poly (L-lactic acid) blend membranes by solution-casting approach

O-Lauroyl chitosan/poly(L-lactide) (OCS/PLLA) blend membranes with different compositions were prepared by solution-casting approach using chloroform as common solvent. The experimental results of FT-IR, DSC and WAXD indicated that inter-association hydrogen-bond interactions existed between OCS and PLLA in the blend membranes. And SEM observation confirmed that the blend membranes with suitable compositions were compatible.     

PPESK纺丝液相分离行为与气体分离膜结构性能的关系

以含二氮杂萘酮结构的聚芳醚砜酮(PPESK)为制膜材料纺制了中空纤维气体分离膜,通过浊点滴定和线性浊点关联式(LCP关系式)计算,对PPESK三元纺丝液体系的相分离行为进行了研究,得到了PPESK三元纺丝液体系相图的相平衡曲线;并由PPESK/N,N-二甲基乙酰胺(DMAc)/γ-丁内酯(GBL)和PPESK/DMAc/丙酸(PA)体系相分离数据计算了PPESK的θ溶剂中GBL和PA与DMAc的比例.结果表明,在PPESK/DMAc/PA和PPESK/DMAc/H2O体系中,浊点滴定实验得到的相平衡曲线与依据LCP关系式计算得到的相平衡曲线吻合;体系热力学性质稳定的纺丝液体系易于制备出结构致密、选择性高的中空纤维气体分离膜;非溶剂添加剂(NSA)/DMAc混合溶剂的θ组成对膜性能有至关重要的影响,NSA/DMAc高于θ组成时,膜性能发生突变,NSA/DMAc低于θ组成时,制得的膜性能良好;力学性能测试表明PPESK中空纤维膜具有良好的机械强度.