Selective swelling of polysulfone/poly(ethylene glycol) block copolymer towards fouling-resistant ultrafiltration membranes

Fouling resistance of ultrafiltration (UF) membranes is critical for their long-term usages in terms of stable performance, so convenient approaches to prepare fouling-resistant membranes are always anticipated. Herein, we demonstrate the facile fabrication of antifouling polysulfone-block-poly(ethylene glycol) (PSF-b-PEG, SFEG) composite membranes. SFEG layer was coated onto macroporous supports and cavitated by immerging them in acetone/n-propanol following the mechanism of selective swelling induced pore generation. Thus-produced SFEG membranes possessed high permeance and excellent mechanical strength. Meanwhile, the structures and separation performances of the SFEG layers can be continuously tuned through simply changing swelling durations. More importantly, the hydrophilic PEG chains were spontaneously enriched onto the pore walls through swelling treatment, endowing intrinsic antifouling property to the SFEG membranes. Bovine serum albumin (BSA)/humic acid (HA) fouling tests proved the prominent fouling resistance of SFEG membranes, and the fouling resistance is expected to be long-standing because of the firm connection between PEG chains and PSF matrix by covalent bonding.     

共聚PP及PP/CaCO3高填充体系的流变行为研究

以双螺杆挤出机制备了共聚PP/CaCO₃高填充复合材料,表征了CaCO₃粒子在基体中的分散行为,并对共聚PP及复合体系的流变行为进行了研究。结果表明:纯共聚PP的熔体呈现出明显的假塑性流体行为,提高熔体温度,熔体的弹性有所增强;高填充共聚PP/CaCO₃复合体系及高填充共聚PP/HDPE/CaCO₃复合体系的熔体的剪切行为与纯共聚PP的类似,高填充的CaCO₃粒子仅对共聚熔体的表观粘度产生轻微影响;共聚PP中大量存在的CaCO₃粒子,降低了熔体的假塑性行为;提高剪切速率是调节高填充共聚PP/HDPE/CaCO3_复合体系粘度的有效手段。     

油酸修饰纳米CaCO3对PP结晶行为和力学性能的影响

Oleic acid (OA)-modified CaCO3 nanoparticles were prepared using surface modification method. Infrared spectroscopy (IR) was used to investigate the structure of the modified CaCO3 nanoparticles, and the result showed that OA attached to the surface of CaCO3 nanoparticles with the ionic bond. Effect of OA concentration on the dispersion stability of CaCO3 in heptane was also studied, and the result indicated that modified CaCO3 nanoparticles dispersed in heptane more stably than unmodified ones. The optimal proportion of OA to CaCO3 was established. The effect of modified CaCO3 nanoparticles on crystallization behavior of polypropylene (PP) was studied by means of DSC. It was found that CaCO3 significantly increased the crystallization temperature, crystal-lization degree and crystallization rate of PP, and the addition of modified CaCO3 nanoparticles can lead to the for-mation of β-crystal PP. Effect of the modified CaCO3 content on mechanical properties of PP/CaCO3 nanocompo-sites was also studied. The results showed that the modified CaCO3 can effectively improve the mechanical proper-ties of PP. In comparison with PP, the impact strength of PP/CaCO3 nanocomposites increased by about 65% and the flexural strength increased by about 20%.     

Preparation and performance of a new sulfonate copolymer scale inhibitor

用水作溶剂,（NH₄）₂S₂O₈/NaHSO₃氧化还原体系作为引发剂,以2-丙烯酰胺基-2-甲基丙烷磺酸（AMPS）、马来酸酐（MA）为单体,与自制的聚乙二醇-衣康酸酯通过溶液聚合制备了一种新型磺酸基聚合物阻垢剂。用红外光谱和热分析方法对聚合物进行了表征和分析。探讨了单体配比、引发剂用量、反应温度对聚合物阻垢性能的影响。结果表明,该共聚物对于碳酸钙盐具有优异的阻垢效果。阻垢剂用量为15 mg/L时,对碳酸钙的阻垢率可达到95%以上。     

Spray coating of polysulfone/poly(ethylene glycol) block polymer on macroporous substrates followed by selective swelling for composite ultrafiltration membranes

Polysulfone(PSF) is extensively used for the production of ultrafiltration(UF) membranes thanks to its high strength,chemical stability,and good processibility.However,PSF is intrinsically hydrophobic,and hydrophilic modification is always required to PSF-based membranes if they are intended to be used in aqueous systems.Facile strategies to prepare hydrophilic PSF membranes are thus highly demanded.Herein we spray coat a PSF-based amphiphilic block polymer onto macroporous substrates followed by selective swelling to prepare flat-sheet PSF UF membranes.The polymer is a triblock polymer containing PSF as the majority middle block tethered with shorter block of polyethylene glycol(PEG) on both ends,that is,PEG-b-PSF-b-PEG.We use the technique of spray coa ting to homogeneously dispense diluted triblock polymer solutions on the top of macroporous supports,instantly resulting in uniform,defect-free polymer coating layers with the thickness down to ～1.2 μm.The bi-layered composite structures are then immerged in ethanol/acetone mixture to generate mesoscale pores in the coating layers following the mechanism of selective swelling-induced pore generation,thus producing composite membranes with the mesoporous triblock polymer coating as the selective layers.This facile strategy is free from additional hydrophilic modification and much smaller dosages of polymers are used compared to conventional casting methods.The pore sizes,porositie s,hydrophilicity,and consequently the separation properties of the membranes can be flexibly tuned by changing the swelling duration and the composition of the swelling bath.This strategy combining spray coating and selective swelling is upscalable for the production of highperformance PSF UF membranes.     

Investigation on Self-assembled Blend Membranes of Polyethylene-block-poly(ethylene glycol)-block-polcaprolactone and Poly(styrene-block-methyl methacrylate) with Polymer/gold Nanocomposite Particles

A block copolymer of polyethylene-block-poly(ethylene glycol) and polycaprolactone was prepared via co-ordination–insertion polymerization. Blend membranes of poly(styrene-block-methyl methacrylate) and polyethylene-block-poly(ethylene glycol)-block-polcaprolactone were used as matrix. Gold/polystyrene nanoparticles were used as nanofiller in polyethylene-block-poly(ethylene glycol)-block-polcaprolactone/poly(styrene-block-methyl methacrylate)/gold/polystyrene nanoparticles membranes. The double gyroid pattern was depicted by blend chains in polyethylene-block-poly(ethylene glycol)-block-polcaprolactone/poly(styrene-block-methyl methacrylate)/gold/polystyrene nanoparticles. An improvement of 22% in tensile strength and 54% in tensile modulus was observed with 1 wt% nanoparticle addition. Polyethylene-block-poly(ethylene glycol)-block-polcaprolactone/poly(styrene-block-methyl methacrylate)/gold/polystyrene nanoparticles 1 showed water flux of 45.2 mL cm^?2 min^?1 and salt rejection ratio of 17.5%. Efficiency of gold nanoparticles–polystyrene nanoparticles reinforced membranes in removal of heavy metal ions was 100%.     

Dual responsive block copolymer coated hollow mesoporous silica nanoparticles for glucose-mediated transcutaneous drug delivery

A self-regulated anti-diabetic drug release device mimicking pancreatic cells is highly desirable for the therapy of diabetes. Herein, a glucose-mediated dual-responsive drug delivery system, which combines pH- and H₂O₂-responsive block copolymer grafted hollow mesoporous silica nanoparticles (HMSNs) with microneedle (MN) array patch, has been developed to achieve self-regulated administration. The poly[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl acrylate]-b-poly[2-(dimethylamino)ethyl methacrylate] (PPBEM-b-PDM) polymer serves as gate keeper to prevent drug release from the cavity of HMSNs at normoglycemic level. In contrast, the drug release rate is significantly enhanced upon H₂O₂ and pH stimuli due to the chemical change of H₂O₂ sensitive PPBEM block and acid responsive PDM block. Therefore, incorporation of anti-diabetic drug and glucose oxidase (GOx, which can oxidize glucose to gluconic acid and in-situ produce H₂O₂) into stimulus polymer coated HMSNs results in a glucose-mediated MN device after depositing the drug-loaded nanoparticles into MN array patch. Both in vitro and in vivo results show this MN device presents a glucose mediated self-regulated drug release characteristic, which possesses a rapid drug release at hyperglycemic level but retarded drug release at normoglycemic level. The result indicates that the fabricated smart drug delivery system is a good candidate for the therapy of diabetes.     

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N₂ permeation, overall porosity, critical water entry pressure (CEP_w), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N₂ permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m^-1. CEP_w of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m^-2·h^-1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.     

衣康酸共聚物合成工艺的优化及其阻垢性能研究

以衣康酸(IA)、烯丙氧基羟丙基磺酸钠(AHPS)、烯丙基聚氧乙烯醚(APEG)为单体,通过自由基聚合的方式,合成出IA-AHPS-APEG三元共聚物。利用中心复合设计法建立了数学模型,结合静态阻碳酸钙垢测试,对聚合反应的引发剂用量、反应温度和反应时间进行了优化。通过FT-IR技术分析了聚合物IA-AHPS-APEG的分子结构,利用TG、SEM和XRD等技术分析了碳酸钙垢和硫酸钙垢的形貌和晶体结构变化,探究了聚合物IA-AHPS-APEG的阻垢机理。结果表明,优化后的IA-AHPS-APEG可以抑制碳酸钙和硫酸钙晶体的正常生长,并使碳酸钙晶体发生晶格畸变,其对碳酸钙的阻垢率最高可达93.2%,对硫酸钙的阻垢率接近100%。     

Time-resolved gel permeation chromatographic study on poly(N-isopropylacrylamide)-block-poly(ethylene glycol) prepared by soap-free emulsion polymerization

To synthesize an amphiphilic block copolymer of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) (NE), an aqueous soap-free emulsion polymerization system was employed where poly(N-isopropylacrylamide) (PNIPA), polymerized from the radically activated chain ends of poly(ethylene glycol) (PEG), forms micelle cores stabilized by PEG brush chains emanating there from. When this polymerization was carried out at temperatures equal to or higher than 34 °C, narrowly-dispersed NE, which cannot be obtained by solution polymerization, was successfully obtained. To elucidate the living nature of the soap-free emulsion polymerization, time-dependent monomer conversion and molecular weight of NE was investigated by time-resolved gel permeation chromatography (GPC). The results indicate that the compartmentalization of end radicals into micelles cores leads to the quasi-living behavior of the polymerization.     

聚丙烯微孔膜的表面矿化修饰及其亲水性能

为了改善聚丙烯微孔膜(MPPM)的表面亲水性,通过组合多巴胺氧化聚合和交替浸渍矿化修饰技术,在MPPM表面构建了均匀的CaCO₃矿物层,实现了利用CaCO₃矿物对膜表面进行亲水化修饰的目的。采用FTIR、XPS、ESEM、EDX和水接触角对矿化膜表面进行了相应的表征。考察了溶液浓度、浸渍循环次数及聚多巴胺涂覆率等对CaCO₃矿化率的影响。结果证实,CaCO₃矿物均匀地负载在MPPM表面,膜的亲水性因CaCO₃固有的润湿性而明显改善。纯水通量测试结果表明,矿化膜具有强的水渗透能力,纯水通量大(高达6450 L·m^-2·h^-1),渗透阻力小,施加0.01 MPa的外压,水即可透过膜。油水乳液分离研究发现,矿化膜能有效地分离一定范围的油水乳液,水通量大(> 1800 L·m^-2·h^-1),且膜容易用水清洗,展现出理想的油水乳液分离应用前景。     

P123对聚醚砜纳米纤维膜结构和性能的影响

通过静电纺丝法制备了聚醚砜(PES)/聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物(P123,PEO₂₀PPO₇₀PEO₂₀,M_a=5800)纳米纤维膜,考察了P123含量对纺丝液的黏度和表面张力的影响,以及对所制备的纳米纤维膜的结构和性能的影响。实验结果表明:P123含量从3%(质量)增至9%时,其纺丝液的黏度由300 mPa·s增至1000 mPa·s,表面张力在36.5～37.8 mN·m^-1范围内;P123改性的PES纳米纤维直径约为360 nm,分布均匀,其表面也比较光滑,取向趋于一致;此外,该纳米纤维膜具有良好的机械性能和耐溶胀性能,较大的比表面积(>39 m²·g^-1),孔隙率,可用作催化剂载体。     

聚砜-纳米Al2O3共混超滤膜的制备与表征

以无机纳米Al2O3粒子作为共混剂与聚砜共混,采用相转化法制得分散均匀的聚砜一纳米Al2O3共混超滤膜。用扫描电镜观察膜表面微观结构及孔分布,测定了膜的孔隙率、纯水通量,并研究了其机械柔韧性能。结果表明,在聚砜膜中适量地添加纳米Al2O3粒子,可改善其亲水性和机械柔韧性能。当添加的Al2O3的质量分数为3％时,膜的水通量和孔隙率最大。     

Effect of Hydrogen Reduction of Silver Ions on the Performance and Structure of New Solid Polymer Electrolyte PEI/Pebax2533/AgBF4 Composite Membranes

In this paper, the effect of hydrogen reduction of silver ions on the performance and structure of new solid polymer electrolyte polyetherimide (PEI)/Pebax2533 (Polynylon12/tetramethylene oxide block copolymer, PA12-PTMO)/AgBF₄ composite membranes is investigated. For PEI/Pebax2533/AgBF₄ composite membranes prepared with different AgBF₄ concentration, the permeances of propylene and ethylene increase with the increase of AgBF₄ concentration due to the carrier-facilitated transport, resulting in a high selectivity. But for propylene/propane mixture, the mixed-gas selectivity is lower than its ideal selectivity. The hydrogen reduction strongly influences the membrane performance, which causes the decrease of propylene permeance and the increase of propane permeance. With the increase of hydrogen reduction time, the membranes show a clearly color change from white to brown, yielding a great selectivity loss. The data of X-ray diffraction and FT-IR prove that silver ions are reduced to Ag⁰ after hydrogen reduction, and aggregated on the surface of PEI/Pebax2533/AgBF₄ composite membranes.     

聚苯乙烯磺酸钠掺杂正渗透膜的制备及其性能

通过两步无皂乳液聚合法,改变第二步对苯乙烯磺酸钠的加入量,制备表面携带磺酸根基团量不同的纳米粒子（PSS）,并将其应用于正渗透（FO）膜的制备。采用红外光谱仪（FTIR）和光电子能谱仪（XPS）表征粒子组成,通过扫描电子显微镜（SEM）表征膜的表面和断面形貌,测定膜孔隙率和亲水性,考察表面磺酸根量不同的聚合物粒子对膜结构性能的影响。结果表明,PSS的引入能提高膜的孔隙率,改善膜的亲水性,且随着粒子表面携带的磺酸根基团量增多,膜的孔隙率与亲水性也随之提高。这是因为PSS粒子可以支撑内部孔道,且表面携带的亲水基团-SO3Na可以提高膜的亲水性,影响活性层的形成。所制备的FO膜性能也得到相应改善,水通量达到了61.1L/(m²·h),为纯聚砜膜的2.8倍,盐截留率达到93.2%,J_s/J_v值仅为0.31g/L,性能得到极大提升。     

Cellulose acetate and sulfonated polysulfone blend ultrafiltration membranes. II. Pore statistics,molecular weight cutoff,and morphological studies

The determination of the pore size, porosity, number of pores, molecular weight cutoff (MWCO), and morphology of an ultrafiltration membrane is necessary for predicting the performance of a membrane for a specific application. For ultrafiltration membranes prepared from cellulose acetate and sulfonated polysulfone in the presence and absence of various concentrations of the additive poly(ethylene glycol) 600, pore statistics and MWCOs were determined in studies with dextrans of different molecular weights. Surface and cross‐sectional morphologies of the membranes were analyzed with scanning electron microscopy at different magnifications. The pore size increased with increasing concentrations of sulfonated polysulfone and additive in the casting solution. Similarly, the MWCOs of the membranes ranged from 19 to 150 kDa, depending on the various polymer blend compositions and additive concentrations. Results from scanning electron microscopy provided qualitative evidence for the trends observed for the pore statistics and MWCO results. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 430–444, 2002; DOI 10.1002/app.10414     

工艺参数对选择性激光烧结PS/SBS/纳米CaCO3制件弯曲强度影响

针对聚苯乙烯(PS)粉末选择性激光烧结(SLS)成型件强度较低的问题,采用机械混合法制备了PS/苯乙烯–丁二烯–苯乙烯嵌段共聚物(SBS)/纳米CaCO₃复合粉末,通过单因素实验分析了SLS工艺参数对成型件弯曲强度的影响,并通过正交试验和极差分析获得了最优工艺参数组合。实验结果表明,烧结件的弯曲强度随着激光功率的增大而升高,随着扫描速度、扫描间距和分层厚度的增大而降低;激光功率对PS/SBS/纳米CaCO₃复合粉末烧结件弯曲强度的影响最大,分层厚度对弯曲强度的影响最小,扫描速度和扫描间距的影响介于两者之间;最佳工艺参数组合为:激光功率27 W,扫描速度1300 mm/s,扫描间距0.24 mm,单层厚度0.22 mm。在此工艺参数组合下PS/SBS/纳米CaCO₃复合粉末烧结件的弯曲强度为13.38 MPa;改性纳米CaCO₃与PS和SBS的相容性较好,能有效起到增强的作用。     

同质增强型PMIA中空纤维膜污染及其MBR工艺处理城市生活污水

以碳酸钙悬浮液、活性污泥混合液及蛋白溶液作为过滤介质,采用标准堵塞过滤和沉积过滤数学模型预测3 h内膜污染类型,结合膜孔径分布、过滤介质粒径分布和污染阻力分布,研究同质增强型聚间苯二甲酰间苯二胺（PMIA）中空纤维超滤膜污染机理。将同质增强型PMIA中空纤维膜应用于MBR系统处理城市生活污水,监测其长期运行的出水水质;借助场发射扫描电镜和特征X射线能谱仪对比分析水洗和化学清洗效果。研究结果表明,当过滤介质为蛋白时,t-t/V线性相关系数为0.9940,膜污染符合标准堵塞模型;当过滤介质为碳酸钙悬浮液和污泥混合液时,V-t/V线性相关系数分别为0.9733、0.9994,二者较为符合沉积模型。应用于MBR中的同质增强型PMIA中空纤维膜对COD、NH₄⁺-N、TP的平均去除率分别为97.78%、96.71%、49.81%,出水水质较好。经化学清洗后膜表面元素接近于原膜,清洗效果较佳。     

可逆加成-断裂链转移聚合制备聚氯乙烯-b-聚乙二醇-b-聚氯乙烯共聚物

合成了含黄原酸酯端基的聚乙二醇（X-PEG-X）大分子链转移剂,并以其为可逆加成-断裂链转移试剂调控氯乙烯（VC）溶液和悬浮聚合,合成聚氯乙烯-b-聚乙二醇-b-聚氯乙烯（PVC-b-PEG-b-PVC）三嵌段共聚物。X-PEG-X调控VC溶液聚合得到的共聚物的分子量随聚合时间增加而增大,分子量分布指数小于1.65。X-PEG-X具有水/油两相分配和可显著降低水/油界面张力的特性,以X-PEG-X为链转移剂和分散剂,通过自稳定悬浮聚合也可合成PVC-b-PEG-b-PVC共聚物,共聚物颗粒无皮膜结构,分子量随聚合时间增加而增大;由于VC悬浮聚合具有聚合物富相和单体富相两相聚合特性,共聚物分子量分布指数略大于溶液聚合共聚物。通过乙酸乙烯酯（VAc）扩链反应进一步证实了PVC-b-PEG-b-PVC的“活性”,并合成PVAc-b-PVC-b-PEG-b-PVC-b-PVAc共聚物。水接触角测试表明PVC-b-PEG-b-PVC的亲水性优于PVC。     

密度和黏结性可控的PE/POE/CaCO3体系颗粒流道调整剂的制备

采用聚乙烯（PE）、聚烯烃弹性体（POE）和碳酸钙（CaCO₃）共混制备了聚合物类颗粒流道调整剂,考察了不同CaCO₃含量和PE与POE比例条件下的PE/CaCO₃、POE/CaCO₃、PE/POE/CaCO₃三类颗粒流道调整剂的密度、熔点熔程、黏结性能、力学性能差异。结果表明,颗粒流道调整剂的密度随CaCO₃含量增加而增大,实现了1.05~1.20 g/cm³范围内可调;结合PE的熔融特性和POE的黏结性能,实现了黏结性能由PE/CaCO₃共混物熔融黏结转为POE/CaCO₃、PE/POE/CaCO₃体系软化黏结的可控调节;通过调节CaCO₃含量、PE与POE比例可以改变流道调整剂颗粒的熔点熔程和拉伸强度,相同CaCO₃含量时PE/POE/CaCO₃体系颗粒的拉伸强度随PE含量升高而增大。