Effect of imidazolium ionic liquid type on the properties of nitrile rubber composites

We investigated the influence of hydrophilic and hydrophobic imidazolium ionic liquids on the curing kinetic, mechanical, morphological and ionic conductivity properties of nitrile rubber composites. Two room temperature ionic liquids with a common cation—1‐ethyl‐3‐methylimidazolium thiocyanate (EMIM SCN; hydrophilic) and 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI; hydrophobic)—were used. Magnesium–aluminium layered double hydroxide (MgAl‐LDH; also known as hydrotalcite) was added to carboxylated acrylonitrile–butadiene rubber (XNBR) whereas fumed silica Aerosil 380 was used in acrylonitrile–butadiene rubber (NBR) as reinforcing fillers. NBR compounds were vulcanized with a conventional sulfur‐based crosslinking system whereas XNBR compounds were cured with MgAl‐LDH. The optimum cure time reduction and tensile properties improvement were obtained when both ionic liquids were added at 5 parts per hundred rubber (phr). The results revealed that EMIM SCN and EMIM TFSI induced an increase in the AC conductivity of nitrile rubber composites from 10^?10 to 10^?8 and to 10^?7 S cm^?1, respectively (at 15 phr ionic liquid concentration). The presence of ionic liquids in NBR slightly affected the glass transition temperature (T_g) whereas the presence of EMIM TFSI in XNBR contributed to a shift in T_g towards lower temperatures from ?23 to ?31 °C, at 15 phr loading, which can be attributed to the plasticizing behaviour of EMIM TFSI in the XNBR/MgAl‐LDH system. Dynamic mechanical analysis was also carried out and the related parameters, such as the mechanical loss factor and storage modulus, were determined. © 2013 Society of Chemical Industry     

Evolution of rheological properties of the nanofluids composed of laponite particles and Mg-Fe layered double hydroxide nanosheets

The thixotropic clay suspensions composed of laponite particles and Mg-Fe layered double hydroxide nanosheets were examined. By adding a very small amount of the layered double hydroxide nanosheets overall rheological properties of the host laponite suspension have been changed. Though the particle concentration of the mixture suspension is only about 1 wt%, the mixture quickly becomes a gel in a day by the electrostatic attraction between nano-materials. When a constant shear rate is applied to the mixture gel suspension, at short time, stress increases linearly with elastic deformation of the mixture. Beyond the maximum of stress, while the solid-like gel structure is being broken down with time of shearing, the stress increases again by reflecting shear enhanced association of solid phase. This is likely that the mixture suspension shows partially the behavior of memory effect.     

Geomaterials: their application to environmental remediation

Abstract

Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. This article reviews three important classes of geomaterials. The first one is smectites—layered silicates with a cation-exchange capacity. Smectites are useful for removing pollutants and as intercalation compounds, catalysts and polymer nanocomposites. The second class is layered double hydroxides (LDHs). They have an anion-exchange capacity and are used as catalysts, catalyst precursors, sorbents and scavengers for halogens. The third class of geomaterials is zeolites—microporous materials with a cation-exchange capacity which are used for removing harmful cations. Zeolite composites with LDHs can absorb ammonium and phosphate ions in rivers and lakes, whereas zeolite/apatite composites can immobilize the radioactive iodine. These geomaterials are essential for environmental remediation.     

Geomaterials: their application to environmental remediation

Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. This article reviews three important classes of geomaterials. The first one is smectites—layered silicates with a cation-exchange capacity. Smectites are useful for removing pollutants and as intercalation compounds, catalysts and polymer nanocomposites. The second class is layered double hydroxides (LDHs). They have an anion-exchange capacity and are used as catalysts, catalyst precursors, sorbents and scavengers for halogens. The third class of geomaterials is zeolites—microporous materials with a cation-exchange capacity which are used for removing harmful cations. Zeolite composites with LDHs can absorb ammonium and phosphate ions in rivers and lakes, whereas zeolite/apatite composites can immobilize the radioactive iodine. These geomaterials are essential for environmental remediation.     

Self-assembly behavior of polymer-assisted clays

Layered silicate clays are natural crystallites that are well recognized for their practical uses, but little is known about their self-assembly behavior. In this review, we summarize the recent literature on clay interactions with organic polymers as well as clay self-assembly with organic involvement. We place emphasis on two aspects of these non-covalent interactions: first, plate-like clays can have a considerable impact on polymer properties such as hydrogels and clay films, and also on the encapsulation of bio-molecules. Second, through ionic intercalation with polymeric amine-salts, the clay layered structure units can be modified and enabled to self-assemble into ordered arrays such as rod-, dendrite-, and fiber-like microstructures. The silicate self-assembled morphologies such as worm-like and hollow microspheres were obtained in epoxy matrices and during spray drying, respectively. A mechanism was proposed for the clay self-assembly in two orientations, platelet face-to-face (ionic attraction) and edge-to-edge (organic hydrophobic effect). Further, the layered clays after the exfoliation into random platelets (1 nm in thickness) had strong propensity toward self-piling without any organic influence. Formation of lengthy rods or fibrils up to 5 μm in length and their hierarchical transformation under transmission electron microscope (TEM) electron beam bombardment and ultrasonication were observed. The clay thin-platelet geometric shape and surface ionic charge are two important parameters for the self-assembling tendency. The high surface of clay platelet has a significant impact on polymer interactions and drives the self-organization of inorganic-organic structures.     

Vaginal suppositories containing Lactobacillus acidophilus: development and characterization

Objective: The aim of this study was to develop and characterize suppositories for vaginal delivery of Lactobacillus acidophilus.

Methods: Formulations were performed in order to select suitable excipients based on suppository formation feasibility and cytotoxicity. Solid body and hollow-type suppositories were prepared by melting and molding using poly(ethylene glycol) (PEG) 400 and 4000 or Witepsol (WIT) H12 as excipients. L. acidophilus was incorporated in the molten mass before molding solid body suppositories or added as suspension into the cavity of hollow-type suppositories and sealed molten excipients. Cytotoxicity of the selected excipients was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and lactate dehydrogenase assays against VK2/E6E7, HEC-1-A and HeLa cells. Suppositories were characterized regarding organoleptic characteristics, mass uniformity, disintegration, breaking strength and L. acidophilus in vitro release.

Results: PEG 400, PEG 4000 and WIT H12 showed the absence of toxicity when tested using three different vaginal cell lines. Obtained vaginal suppositories presented uniform and mild texture, a content of about 1?×?10⁸ colony-forming units, completely disintegrated in simulated vaginal environment in less than 60?min and provided sustained in vitro release of L. acidophilus. Release studies further demonstrated that incorporation of freeze-dried bacteria did not result in significant loss of viable bacteria, thus supporting that vaginal suppositories may possess good properties to promote the replacement of the vaginal flora in situations of urinary tract infection.

Conclusion: Hollow-type suppositories showed to be promising delivery vehicles for vaginal delivery of probiotics.     

水滑石在阻燃聚丙烯腈纤维改性中的应用研究

在经十二烷基硫酸钠柱撑的水滑石层间进行丙烯腈的原位聚合反应，用红外光谱和X-射线衍射对聚合物样品进行了结构分析与表征，并对聚丙烯腈／柱撑水滑石共混物样品的燃烧性能进行了研究。结果表明：丙烯腈单体在水滑石片层之间发生原位聚合反应，生成聚丙烯腈大分子，并使水滑石片层间距有一定程度的增大；共混物的极限氧指数从18．1％提高到了25．5％，同时共混物的热重曲线向高温方向发生了偏移，阻燃性能得到一定程度改善。     

A review of botanical characteristics, phytochemistry, clinical relevance in efficacy and safety of Lycium barbarum fruit (Goji)

Lycium barbarum has been used as a traditional Chinese medicine (TCM) to nourish liver and kidney, and brighten the eye. The fruits are dried or freshly squeezed for their juice and concentrated for beverages. Among various constituents, a group of polysaccharides (LBP) with a Glycan-O-Ser glycopeptide structure has been most researched and considered to be important for the efficacy of L. barbarum. Studies indicate effects of L. barbarum on aging, neuroprotection, general well-being, fatigue/endurance, metabolism/energy expenditure, glucose control in diabetics, glaucoma, anti-oxidant properties, immunomodulation, anti-tumor activity and cytoprotection. In addition to TCM, L. barbarum can be sold as a dietary supplement or classified as a food based upon the long and safe traditional usage. This review is to provide background and updated information of chemical constituents and efficacies with safety including a new direction for research and current regulatory situation of L. barbarum.     

Phytochemistry and medicinal uses of the bael fruit (Aegle marmelos Correa): A concise review

Aegle marmelos, a plant indigenous to India has been used by the inhabitants of the Indian subcontinent for over 5000 years. The leaves, bark, roots, fruits and seeds are used extensively in the Indian traditional system of medicine the Ayurveda and in various folk medicine to treat myriad ailments. Bael fruits are of dietary use and the fruit pulp is used to prepare delicacies like murabba, puddings and juice. Bael fruits are also used in the treatment of chronic diarrhea, dysentery, and peptic ulcers, as a laxative and to recuperate from respiratory affections in various folk medicines. Scientific studies have validated many of the ethnomedicinal uses and reports indicate that the fruit possesses broad range of therapeutic effects that includes free radical scavenging, antioxidant, inhibition of lipid peroxidation, antibacterial, antiviral, anti-diarrheal, gastroprotective, anti-ulcerative colitis, hepatoprotective, anti-diabetic, cardioprotective and radioprotective effects. For the first time, this review critically assesses the nutritional values, phytochemistry and preclinical pharmacological properties of the bael fruit. Attempts are also made at emphasizing the dietary and pharmaceutical potential of bael fruit that has been largely underutilized and neglected.     

植物乳杆菌乳酸脱氢酶的抽提与初步纯化

研究了从植物乳杆菌RS2 2中提取胞内乳酸脱氢酶的工艺过程,探讨了超声破碎时菌体质量浓度、处理量及处理时间对破碎效果的影响;对酶的提取工艺研究表明,0.05mol/L磷酸缓冲液(pH7.0)添加0.10～0.30mol/LNaCl可达到较好的抽提效果;对硫酸铵盐析去杂蛋白质及DEAE离子交换层析工艺进行了初步优化.在优化的工艺条件下,酶的总回收率为40.2%,比酶活提高到原来的18.9倍.