Photo-induced anisotropy in ZnO/PVA nanocomposites prepared by modified electrochemical method in PMA matrix

Substantial photo-induced optical anisotropy was discovered in ZnO/PVA nanocomposites under the influence of external bicolor laser illumination. Zinc oxide nanoparticles were synthesized by electrolysis of a sodium chloride aqueous medium including poly-methacrylic acid (PMA) in a cell system having a soluble zinc anode. The structural analysis of the ZnO powder samples has been carried out by X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM). The polyvinyl alcohol (PVA) embedded ZnO films obtained from the powder samples possess larger grain sizes than those in powder form. The films were prepared from the same polymer matrix but elaborated with two different PVA contents which are respectively 15% and 30%. The photoinduced anisotropy was identified by using two bicolor Er: glass laser beams incident at different angles. Substantial influence of the technological processes on the embedded nanoparticle sizes and related birefringence was explored. The process of laser induced anisotropy shows an occurrence of birefringence saturation.     

Effects of polyethyleneimine-functionalized MCM-41 on flame retardancy and thermal stability of polyvinyl alcohol

Hyperbranched polyethylenimine (PEI)-functionalized mesoporous silica (MCM@PEI) was synthesized and used to produce poly(vinyl alcohol) (PVA) nanocomposites. The modified nanofiller was characterized with infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N₂ adsorption. When compared with pure mesoporous silica (MCM), the MCM@PEI nanoparticles exhibited better dispersion in the PVA matrix. The effects of MCM@PEI on the thermal and flame properties of PVA nanocomposites were also studied. Improvement in the thermal properties was confirmed by enhanced thermal stability and char yield. Incorporation of MCM@PEI in PVA led to a significant drop in the heat release rate and the total heat release.     

改性淀粉/PVA生物降解材料性能的研究

以BPO为引发剂、正庚烷为溶剂在66℃下制得马来酸酐接枝淀粉。将其与聚乙烯醇(PVA)、增塑剂及加工助剂等于HAAKE密炼机中共混,制备了可生物降解热塑性淀粉塑料。研究了接枝改性淀：粉／PVA共混物的力学性能、生物降解性能及热性能等,并用SEM研究了共混物的微观形态。结果表明接枝改性淀粉／PVA共混物拉伸强度为27．57Mpa,60d失重率达65．1％。     

SULPHONATED POLY ETHER ETHER KETONE/ POLYVINYL ALCOHOL/PHOSPHOTUNGSTIC ACID COMPOSITE MEMBRANES FOR PEM FUEL CELLS

Composite membranes with polyvinyl alcohol (PVA),sulphonated poly ether ether ketone (SPEEK) and phosphotungstic acid (PWA) were prepared using solvent casting method.The proton conductivities of such membranes were found to be in the order of 10~(-3) S/cm in the fully hydrated condition at room temperature as measured by impedance spectroscopy.The crystalline properties were studied by X-ray diffraction analysis.The thermal properties were determined by TGA and DSC techniques.The tensile strength and pe...     

Polyamide-imide/polyetherimide dual-layer hollow fiber membranes for pervaporation dehydration of C1–C4 alcohols

To circumvent the common swelling and deteriorated performance of integral asymmetric hollow fiber membranes for pervaporation dehydration, we have developed novel polyamide-imide (PAI)/polyetherimide (PEI) hollow fiber membranes with synergized performance with the aid of dual-layer spinning technology. Dehydration of C1–C4 alcohols has been conducted and the orders of their fluxes and permeances have been analyzed. The hollow fibers spun at 2 cm air gap and annealed at 75 °C exhibit the highest pervaporation performance: separation factors for t-butanol/water and iso-butanol/water binary systems are greater than 50,000 with flux more than 700 g/m² h. A comparison with literature data shows that the newly developed membranes outperform most other polymeric membranes for the dehydration of IPA and butanols. The dual-layer hollow fiber membranes also exhibit good long-term stability up to 200 h. The superior performance can be attributed to (1) the balanced properties of PAI as the selective layer for dehydration pervaporation; (2) the low water uptake and less swelling characteristic of the PEI supporting layer; and (3) the desirable membrane morphology consisting of a fully porous inner layer, a porous interface, and an ultrathin dense-selective outer skin.     

Effectiveness of natural and synthetic blocking reagents and their application for detecting food allergens in enzyme-linked immunosorbent assays

Blocking is an important step before an enzyme-linked immunosorbent assay (ELISA) can be performed. It reduces non-specific binding to the microtiter plate to a minimum. For detecting food allergens by means of ELISA, the problem with protein blocking solutions is obvious. The blocker might interfere with the antibodies of the assay and leads to false positive results. Therefore, other blocking solutions are greatly needed. There are some alternatives like synthetic blockers or carbohydrates. Comparisons of these different blocking agents, namely proteins, carbohydrates, and synthetic blockers, were made at different reaction conditions. The incubation periods and temperatures were varied, as well as the pH. The best combinations were evaluated and compared, in respect of their blocking efficiency. The two best non-proteinaceous blockers, i.e. polyvinylalcohol and Ficoll, were subsequently applied to ELISA tests for the determination of α-casein and peanut. The study showed that Ficoll and PVA did as well as BSA in buffer solution. Therefore, they can be considered as alternative blocking reagents for ELISA, especially for the detection of food allergens.     

高强度聚乙烯醇水凝胶微球的制备

以三氯甲烷/丙酮为凝固液, 用高压静电技术制备了高强度、物理交联的聚乙烯醇(PVA)水凝胶微球. 研究了凝固液组成、PVA溶液浓度、温度和湿度、电场强度、进样速度及微球冷冻次数等对PVA微球的形貌、粒径和强度的影响. 结果表明, 采用常压水蒸气控制PVA溶液温度与湿度的高压静电技术, 可克服高浓度PVA溶液在强电场下出现微丝现象, 形成的水凝胶微球具有强度高、粒径在一定范围内可控的特点.     

反气相色谱法与Hansen溶解度参数法测定聚乙烯醇溶解度参数及相关热力学性质

采用反气相色谱（IGC）法,以聚乙烯醇（PVA）为固定相,脂肪族、芳香族、醇、酮及卤代烃5类18种化合物为探针分子,研究PVA的溶解性质并获得了PVA在383.15～423.15 K范围内的溶解度参数（δ₂）及相关热力学性质,并与Hansen溶解度参数法（HSP）测得的溶解度参数（δ_T）进行比较。结果表明,5类溶剂对PVA溶解能力的趋势为酮类 >醇类 >卤代烃、芳香类、脂肪族类>脂环族,卤代烃、芳香类和脂肪族类溶剂的溶解能力相似;在测试温度范围内PVA的δ₂随温度升高而增加;采用IGC法外推出室温（298.15 K）下PVA的δ₂为27.69 （J/cm³）^0.5,与HSP法测得室温下PVA的δ_T（27.77 （J/cm³）^0.5）一致。PVA溶解度参数及相关热力学参数的研究为其应用及相关研究提供了定量依据。     

PVA栅绝缘层浓度对P3HT有机场效应晶体管性能的影响

采用溶液制备法制备了用PVA作为绝缘层、P3HT作为有源层的有机场效应晶体管,,研究了不同浓度PVA栅绝缘层对器件性能的影响。实验结果显示,以质量分数为8%的PVA溶液制备的栅绝缘层具有最好的性能,器件的场效应迁移率为0.31 cm²·V^-1·s^-1,阈值电压为-6 V。进一步分析了PVA栅绝缘层浓度对器件性能提高的原因,结果表明,对于制备溶液化的有机场效应晶体管,选取合适的PVA栅绝缘层浓度非常重要。     

煅烧温度对Cu掺杂ZnO纳米粉体的制备及发光性能的影响

在PVA溶液中制备ZnO∶Cu纳米粉体的前驱体,经过煅烧获得ZnO∶Cu纳米粉体,考察煅烧温度对制备过程及发光性能的影响。利用XRD、TEM分析了产物的结构和形貌,XRD分析结果表明,当煅烧温度高于500℃时,可以使PVA完全分解,制备出具有六角纤锌矿结构的ZnO∶Cu粉体。TEM结果表明,粉体呈球形,大小均匀,分散性好,平均粒径为20～25 nm。在342 nm波长光的激发下,在ZnO∶Cu的室温PL光谱中可以观察到两个中心波长位于458 nm和486 nm的较强的蓝光发射峰,经400℃煅烧处理的ZnO∶Cu纳米粉体的蓝光发射最强。煅烧后的ZnO∶Cu只有微弱的绿光发射(510～530 nm),Cu的掺杂使ZnO的绿光发射变为蓝光发射。蓝紫光的发射波长随煅烧温度的升高产生明显的红移,由300℃时的404 nm红移至600℃时的422nm,发射强度随温度升高先增大后减小。