聚丙烯腈基不对称膜相转化过程中孔结构形成研究

采用L-S相转化法制备聚丙烯腈不对称膜,使用光学显微镜测试非溶剂在铸膜液中的扩散速率,结合光穿透实验、扫描电子显微镜及气体渗透性能测试结果,研究相转化过程中溶剂种类、铸膜液浓度及蒸发时间对成膜过程中孔结构形成过程的影响.结果表明:成膜工艺对相转化过程中的孔结构的形成有明显影响.不同溶剂制备的铸膜液其黏度及溶剂与非溶剂溶解度参数差不同,影响非溶剂在铸膜液中扩散系数.增加铸膜液浓度,其黏度增加;延长蒸发时间,膜的致密层厚度增加,二者都使非溶剂在铸膜液中的扩散系数下降,从而影响相转化过程中孔结构的形成.     

非溶剂添加剂对PES／NMP铸膜液性质的影响

依据文献报道的PES／NMP（聚醚砜／N－甲基吡咯烷酮）制膜体系的浊点数据和特性粘数,从传统的宏观热力学和铸膜液中高分子的构象两方面讨论了非溶剂添加剂的种类和加入量（邻近比）对PES／NMP铸膜液性质的影响。非溶剂添加剂改变了PES／NMP铸膜液的热力学性质和PES分子的构象。这种效应依非溶剂种类的不同而显著不同。非溶剂添加剂对铸膜液性质的影响不仅表现在种类的差别上,也和无因次量－－邻近比密切相关。邻近比可以表征铸膜液的热力学状态和混合溶剂的质量。铸膜液的邻近比增大,混合溶剂的质量下降,铸膜液的热力学稳定性降低,PES分子的构象也由舒展状态逐渐收缩。聚合物分子的构象对成膜过程的影响十分显著,研究成膜机理不能忽视非溶剂添加剂对铸膜液中高分子构象的影响。     

蒸发诱导相分离对聚砜膜结构及性能的调控EI北大核心CSCD

为减缓非溶剂诱导相分离过程中的溶剂与非溶剂之间的质量交换,延迟相转变过程,在铸膜液浸入凝固浴前引入蒸发诱导相分离,通过调节蒸发诱导时间和环境温湿度改变聚砜膜的内部结构及性能。研究表明,随着预蒸发时间的延长,铸膜液质量呈近似线性增加,水蒸气浸入铸膜液的速率高于铸膜液内溶剂的蒸发速率。同时断面形貌图显示,膜孔的形状从典型的指状孔逐渐消失转变为大小均一的细胞状圆孔,表皮层细胞状圆孔的厚度在整个膜截面中也不断增加,直到25 min时,膜截面的指状孔逐渐消失。环境温度升高(湿度减小)加快了1-甲基-2-吡咯烷酮(NMP)与水蒸气之间的质量交换导致指状孔结构出现。在相同蒸发温度时,膜孔隙率从78.39%降至61.12%,平均通孔孔径从0.0616μm降至0.0219μm,水通量从948.85 L/(m^(2)·h)降至4.533 L/(m^(2)·h)。但经过预蒸发过程后的膜力学性能都有所提升。     

CA／CAT共混不对称纳滤膜制备过程中的影响因素探讨

用相转化法制备ＣＡ／ＣＴＡ不对称纳滤一醋酸纤维素（ＣＡ）和三醋酸纤维素（ＣＴＡ）的相对比例，混合溶剂以及其中高挥发性组分的比例，加剂在铸膜液中的含量，铸膜液２以及制膜条件（蒸发时间、凝胶浴组成和温度、热处理时间）对所制膜的性能都有很大的影响，这些因素主要是通过改变皮怪中高聚物聚集体孔和网络的大小和数目来影响所制膜的性能，高聚物聚集体孔上和数目对所制膜的通量截留率起主要作用。     

热力学及动力学因素对L-S相转化法制备非对称膜结构与性能的影响

采用L-S相转化法制备非对称型分离膜的结构与性能取决于其制膜过程的热力学及动力学因素,讨论了聚合物分子量及浓度、溶剂及溶剂化作用、添加剂、铸膜液温度等热力学因素对铸膜液结构的影响,以及溶荆蒸发速度、凝胶速度等动力学因素对于脱溶剂速度的影响,综述了相关的热力学及动力学影响因素的表征方法.     

蒸发对新型聚芳醚腈酮超滤膜性能的影响

以聚芳醚腈酮(PPENK)为膜材料,以氮甲基吡咯烷酮为溶剂及添加剂制成稳定的铸膜液,使用水为凝胶浴,相转化法制备PPENK超滤膜．研究了铸膜液在空气中的蒸发温度及时间对超滤膜孔隙率、孔结构、纯水通量及截留率等膜性能的影响．结果表明,在实验室所选择的蒸发时间和蒸发温度范围内这两种因素对超滤膜性能影响不大,通过控制合适的蒸发时间和蒸发温度,可以制得具有高通量和高截留率而且表面无缺陷结构高质量超滤膜．     

CA/CTA共混不对称纳滤膜制备过程中的影响因素探讨

用相转化法制备ＣＡ／ＣＴＡ不对称纳滤膜．二醋酸纤维素（ＣＡ）和三醋酸纤维素（ＣＴＡ）的相对比例,混合溶剂以及其中高挥发性组分的比例,添加剂在铸膜液中的含量,铸膜液浓度以及制膜条件（蒸发时间,凝胶浴组成和温度,热处理时间）对所制膜的性能都有很大的影响．这些因素主要是通过改变皮层中高聚物聚集体孔和网络孔的大小和数目来影响所制膜的性能．高聚物聚集体孔的大小和数目对所制膜的通量和截留率起主要作用．     

改性淀粉膜的制备及生物降解性能

以控制释放肥料为模型,采用膜失重率法、膜形态分析法和CO2产量测定法考察了不同成膜因素如取代度、铸膜液溶剂及铸膜液浓度对酯化改性淀粉膜生物降解性能的影响。结果表明,改性淀粉取代度越高,铸膜液溶剂挥发性越低,铸膜液浓度为16%时,膜土壤降解速率越小。30℃恒温时,初步优化的改性淀粉膜在土壤中30d失重率为20%,21d降解成CO2的比率为1.98%。改性淀粉膜在土壤中能降解且有较小降解速率,能够满足控制释放肥料对膜降解性的要求。     

改性淀粉膜的制备及生物降解性能EI北大核心CSCD

以控制释放肥料为模型,采用膜失重率法、膜形态分析法和CO2产量测定法考察了不同成膜因素如取代度、铸膜液溶剂及铸膜液浓度对酯化改性淀粉膜生物降解性能的影响。结果表明,改性淀粉取代度越高,铸膜液溶剂挥发性越低,铸膜液浓度为16%时,膜土壤降解速率越小。30℃恒温时,初步优化的改性淀粉膜在土壤中30d失重率为20%,21d降解成CO2的比率为1.98%。改性淀粉膜在土壤中能降解且有较小降解速率,能够满足控制释放肥料对膜降解性的要求。     

PVDF在空纤维滤膜的形态结构

用Ｌ－Ｓ相转换法制备了聚偏氟乙烯中空纤维不对称滤膜，铸膜液由聚合物，溶剂和添加剂组成。用电子显微镜考察了聚合物浓度，添加剂用量及种类对膜形态结构的影响。     

Polyamide 4,6 membranes for the encapsulation of Langerhans islets: preparation, physico-chemical properties and biocompatibility studies

Porous polyamide 4,6 membranes developed as semi-permeable and biocompatible membranes for the encapsulation of pancreatic islets were prepared by precipitation in water. Different membrane morphologies were obtained by varying the molecular weight of polyamide 4,6, the solvent evaporation time and the composition of the casting solution. Each membrane was submitted to differential scanning calorimetry and water flux measurements to study the total water content and the different kinds of water in correlation with its permeability performances. Their biocompatibility was first evaluated by a surface protein adsorption test. Of the various membranes, the one prepared by immersion in water after 5 minutes of solvent evaporation, of 15% KS200 polyamide 4,6 solution added with 1% of polyvinylpyrrolidone K30 seems to be the most promising. This membrane is characterized by a low adsorption of proteins, a high hydraulic coefficient and an asymmetric structure. Such a membrane represents a good candidate to be an efficient immunological barrier. It also exhibits good glucose and insulin diffusion properties. Moreover, rat islets cultivated on its surface were not affected by its presence and no important cell adhesion was noticed when implanted in mice. This membrane exhibits most of the properties suitable for the islet encapsulation with a view to developing a bioartificial pancreas.     

Influence of cross-linking density on swelling and estradiol permeation of chitosan membranes

Chitosan membranes were obtained by a casting/solvent evaporation method and cross-linking with sodium tripolyphosphate. The effect of cross-linking time was studied and the cross-linked membranes were characterized with respect to equilibrium water content, sodium content, IR spectroscopy and permeability to a model drug (Estradiol). Sodium content increased with increasing cross-linking time. Equilibrium water content was higher in the membrane with the lowest cross-linking time. This membrane also showed a higher flux of Estradiol compared with the other which exhibited an increment in equilibrium water content and flux of Estradiol with the increase in cross-linking duration. These dissimilar results could be explained by a significant correlation between the hydrophilicity of the membrane and the hydrophobicity of Estradiol.     

聚酰胺复合膜的改性及其选择渗透性

非对称性的反渗透(RO)聚酰胺(PA)复合膜可以通过溶剂处理方法改性成为渗透汽化(PV)分离有机物水溶液的均相膜．实验选用了PA良溶剂(甲酸、乙酸、磷酸、盐酸、苯酚)作为PA膜的改性剂．溶剂改性条件(改性剂类型、浓度和处理时问)对改性膜的吸着性有明显影响．用质量分数8％的乙酸处理1h的PA膜，较之未改性膜，优先吸水性增强，对水的溶胀率SW增大，对异丙醇的溶胀率SIPA减小．乙酸处理的PA膜的SW与SIPA差值在所有溶剂处理的膜中最大，相应地PV分离IPA水溶液时，膜的分离因子和渗透通量也最大，处理过程溶剂分子与PA高分子链的接触和PA膜中微囊内高分子链段向外运行，是PA膜结构改变的主要因素．溶剂处理改变了膜的结构的机理能很好地解释非对称性RO膜的改性．     

壳聚糖复合不对称膜的制备及生物组织相容性研究

用分步流延干燥法制备了一种由壳聚糖（CS）、聚乙烯醇（PVA）、羧甲基壳聚糖（CM-CS）构成的新型人工皮肤医用材料——壳聚糖复合不对称膜（C-P-C膜），其上层为CS层，中间为PVA层，下层为CM-CS层。研究结果表明，可通过调节CS、PVA、CM-CS的加入量来控制复合不对称膜各层的厚度和膜的水蒸气通透性，C-P-C膜具有良好的透光性和吸水率。生物相容性实验发现，C-P-C膜是无毒材料，不会引起创伤感染，随着植入C-P-C膜时间的延长，组织炎症反应明显减轻，6周时，炎症浸润程度低于手术缝合线。C-P-C膜能够明显地促进创面愈合，能有效地密封出血创面且具有显著的止血作用。     

Processes and states during polymer film formation by simultaneous crosslinking and solvent evaporation

Coating film formation with simultaneous crosslinking and solvent evaporation, accompanied by passage of the polymer film through glass transition region, is a complex process by which temporary or permanent anisotropic and gradient network structures can be formed. Evaporation and crosslinking are processes that are interdependent. The changes in structure (growth of branched molecules and network evolution) are a function of reaction kinetics, which gets diffusion controlled when the system passes through the glass transition region. Structural changes are determined by branching, gelation, and network build-up and depend on the architecture of network precursors. Thermodynamic interactions of polymer with solvents affect the solvent activity which determines the vapor pressure of the solvent over the film and thus the evaporation rate. The glass transition temperature increases as a result of both the decreasing solvent content and conversion of functional groups into bonds. By interplay of these two factors more or less solvent can be locked in by vitrification. The roles and intensity of these basic processes and interrelations are discussed. Some older results are reviewed and new experimental evidence is added. The interrelations are illustrated by time dependences of solvent evaporation and conversion of functional groups for solvent-based high-solids polyurethane systems composed of a hydroxyfunctional star oligomer and triisocyanate and by the role of the ratio of evaporation to crosslinking rates. Evidence was obtained of gradient formation in which appearance of a glassy surface layer is an important event in the history of film formation that determines solvent retention and other film characteristics.     

Asymmetric polyurethane membrane with inflammation-responsive antibacterial activity for potential wound dressing application

By combining solvent evaporation with wet phase inversion technique, an asymmetric polyurethane membrane (ASPU) was constructed from a sulfanilamide-conjugated PU, as a potential candidate for wound dressing application. As a result of the combined membrane-formation method, the ASPU membrane was constituted by an integral and dense skin layer supported by a porous sublayer. The skin layer was found impermeable to pathogenic organisms, while the sublayer was intended for draining excessive exudates. Compared with typical PU membrane dressings commercially available, the ASPU membrane exhibited a reasonable moisture vapor transmission rate, as well as significantly improved gas circulation and exudate absorption capabilities, which synergistically optimized the wound microenvironment for proper healing. Furthermore, the sulfanilamide-conjugated PU constituting ASPU membrane was designed as susceptible to urease, a representative hydrolase derived from inflammation-causing pathogens. In the presence of urease, urea linkages adjacent to sulfanilamide monomeric units were found catalytically cleaved, enabling release of free antibiotic sulfanilamide that held pharmacological activity from ASPU membrane. When incubated without urease, those cleavage sites exhibited substantially high resistance against hydrolysis so that no sulfanilamide release was detected throughout the incubation period. In this inflammation-responsive manner, the anti-inflammatory efficiency of antibiotics was significantly enhanced, while undesirable side effects associated with antibiotic abuse was minimized. Cell culture assay further revealed that the ASPU membrane displayed no cytotoxicity toward normal human dermis fibroblasts, suggesting a biocompatible potential. Based on these results, the multifunctional ASPU membrane designed in this study might be clinically suitable as an ideal biomedical dressing for wound care.     

Development of asymmetric gradational-changed porous chitosan membrane for guided periodontal tissue regeneration

A novel kind of guided tissue regeneration (GTR) barrier membrane has been fabricated using an immersion–precipitation phase inversion technique (IPPI) with biodegradable natural polymer–chitosan. The membrane had an asymmetric gradational-changed porous structure including a dense skin layer, a transition region and a sponge-like porous layer. The concentration of chitosan solution and solvent evaporated time were two key factors that had significant effect on the porosity, average pore size, absorbed water ratio and mechanical properties of the porous membrane. The porous membrane not only degraded but maintaining the structure integrity for 5–6 weeks in the enzyme solution that can meet the demand for GTR. The biological experiment results showed the asymmetric membranes did not cause anaphylactic reaction, hemolysis, cytotoxicity and pyrogenic effect. All of the results indicated that the porous chitosan membrane had excellent biocompatibility and biodegradation, which could be used as a barrier for preventing apical migration of gingival epithelial cells and promoting growth of periodontal ligament cells in periodontal therapy.     

蒸发时间对两级凝胶法制备的聚醚砜膜结构和性能的影响

主要探讨了蒸发时间对用两级凝胶法(dual—bath coagulation method)所制得的聚醚砜(PES)超滤膜的性能和结构的影响．结果表明，随着蒸发时间的延长，水通量先减小后增大；肌肝和尿素去除率均是先升高而后降低，然后再升高的趋势；膜的孔隙率上升，平均孔径下降．在蒸发时间为10s时，肌肝和尿素去除率最高，且水通量适中，是血液净化用聚醚砜膜的最佳成形条件．