Effect of Polyvinylpyrrolidone on Separation Performance of Cellulose Acetate-Polysulfone Blend Membranes

Blend membranes comprising cellulose acetate and polysulfone (CA/PSf) were prepared through a solution casting method using a different concentration of polyvinylpyrrolidone (PVP) as the pore former. Fourier transform infrared spectroscopy (ATR-FTIR) was used to investigate structural properties of membranes. Membranes morphology and its thermal properties were characterized by scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The strength of membranes was studied by mechanical stability. The effect of PVP concentration on separation performance of the prepared membranes was studied. The separation performance of prepared membranes was tested by using an aqueous solution of cadmium metal complexed with humic acid. The results showed that an increase in the PVP concentration in the cast film from 0 to 3 wt% increased the thermal stability, water content (%), pure water flux, and solute rejection. SEM results showed that the pore size decreased but the number of pores increased on an increase in the PVP concentration.     

Ferroelectric liquid crystal dopants with a chiral (R,R)‐2,3‐difluorooctyloxy side‐chain: host dependence of the polarization power

The polarization powers δ_p of four chiral dopants with (R,R)‐2,3‐difluorooctyloxy side‐chains were measured in four liquid crystal hosts with isotropic (I)–nematic (N)–smectic A (SmA)–smectic C (SmC) phase sequences. The four chiral dopants differ in terms of their core structures: 2‐phenylpyridine (MDW950), biphenyl (5), 2‐phenylpyrimidine (6) and 2‐(3‐nitrophenyl)pyrimidine (7). In each case, δ_p varies with the structure of the liquid crystal host, which is consistent with the behaviour of so‐called Type II dopants that normally feature a chiral core structure. The δ_p(host) profile was found to depend on the degree of biaxiality of the dopant core structure, and on the degree of steric coupling between the chiral 2,3‐difluorooctyloxy side‐chain and the core. Conformational analyses at the B3LYP/6‐31G* level suggest that the 2,3‐difluorooctyloxy side‐chain is conformationally more rigid than conventional chiral side‐chains due to the added electrostatic repulsion of the two adjacent fluoro groups combined with the hyperconjugative ‘gauche effect’, and may therefore have a higher degree of biaxiality on the time average. This biaxial character should make the chiral side‐chain more sensitive to variations in quadrupolar ordering imposed by the SmC phase of the liquid crystal host, and may therefore explain the dependence of δ_p on the host structure reported herein.     

Phase diagrams and morphology of polymer-dispersed liquid crystals: An analysis

Thermal and morphological studies of polymer-dispersed liquid crystals (PDLCs) for various compositions of liquid crystalline material 4-undecyloxybenzoic acid (UDBA) in two polymer matrices, polyvinylidenefluoride-co-hexafluoropropylene P(VdF–HFP) or polyethylene oxide (PEO), have been carried out using differential scanning calorimetry (DSC) and polarising optical microscopy (POM). Phase diagrams for different series of PDLCs have been analysed using the Flory–Huggins theory of isotropic mixing and the Maier–Saupe–McMillan theory, to include the anisotropic contributions. Mesogenic transitions of UDBA are observed to be greatly influenced when dispersed in these polymers. The morphologies and miscibility studies of these PDLCs suggest that UDBA is highly miscible in PEO, only partially miscible in poly(methyl methacrylate) (PMMA), but almost immiscible in P(VdF–HFP).     

The influence of solution‐state conditions and stirring rate on the assembly of poly(acrylic acid)‐containing amphiphilic triblock copolymers with multi‐amines

In the effort towards making nanoscale objects and assemblies feasible for use as functional materials, it is imperative to obtain control over the fundamental architectures and essential to understand what experimental conditions cause the manifestation of specific morphologies. A number of factors are known to influence the shape during the self‐assembly of amphiphilic block copolymers in solution, including solvent composition, polymer length, hydrophobicity versus hydrophilicity, as well as the addition of additives that can interact with segments of the block copolymers. This research, focused on developing an understanding of the micellar architectures accessed by the amphiphilic triblock copolymer of acrylic acid, methyl acrylate, and styrene, PAA₈₅‐b‐PMA₄₀‐b‐PS₃₅, as a function of the stirring rate, together with other factors, when undergoing coassembly with ethylenediamine or diethylenetriamine in water/tetrahydrofuran solutions. The work demonstrates that the rate at which the polymer solution was stirred impacts the shape of the solution‐state assemblies formed by the triblock copolymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Fracture Behavior of Covalently Re-Modified MWNT/Epoxy Nanocomposites

Summary: In this work, a surface re-modified multi-walled carbon nanotube (MWNT) was prepared by the chemical attachment of oligomeric unsaturated polyester on the MWNT surface. The re-modified MWNT was incorporated in two concentrations of 0.35 and 0.70 Wt.% into epoxy resin in order to investigate its effect on morphology and mechanical behavior of the MWNT/epoxy nanocomposite. The transmission electron microscopy showed that the re-modification of MWNT surface improves its dispersion state in the epoxy matrix. The tensile measurements for the nanocomposite having different amounts of surface re-modified/not-modified MWNT showed that the fracture mechanism changed from brittle to tough beyond a certain amount of surface re-modified MWNT. The scanning electron microscopy findings on the fracture surface morphology of the resulted nanocomposite substantiated the observed phenomena.     

特殊形貌CdSe纳米晶的制备

CdSe纳米晶是II-VI族半导体中研究最多的材料之一,由于其发射波长随纳米晶的尺寸而改变,从而可以覆盖从绿到红的宽光谱范围,因此CdSe纳米晶可以应用于生物标记和荧光显示等领域,各种制备CdSe纳米晶的方法也应运而生。因制备方法的不同,所得CdSe纳米晶的粒径、相结构及形貌也不同,进而影响CdSe纳米晶的性质。本文归纳了7种典型的制备一些特殊形貌的CdSe纳米晶的最新方法,并对各种方法的优缺点作了简单评价。最后,对这一领域未来的研究和发展方向作了展望。     

凝胶介质中仿生矿化过程的研究

本文综述了凝胶介质中仿生矿化过程的研究进展。仿生矿化是当前化学、生物学和材料科学的研究前沿和热点。近年来,越来越多的生物学证据表明：生物体中的蛋白质和多糖等生物大分子,往往通过超分子组装形成凝胶状基质网络,进而对生物矿化过程施加影响。因此,凝胶介质中的仿生矿化研究对深入了解生物矿化机理,以及从理论上指导先进功能材料的设计和合成具有重要意义。迄今为止,研究人员已经对天然和合成高分子凝胶、超分子水凝胶和无机凝胶等多种凝胶介质中的仿生矿化过程进行了研究。结果表明：凝胶介质主要通过其三维网络结构限制反应离子在其内部的扩散速率,并掺杂到无机矿物的晶体结构中,从而影响生成晶体的形貌和构造。而且在有机基质(如水溶性有机高分子和自组装单层等)的协同作用下,凝胶介质中的仿生矿化过程也呈现出与水溶液中不同的特点。此外,本文还介绍了当前对凝胶介质中矿物形貌的调控和矿化机理的几种不同观点,并对该领域未来的研究和应用进行了展望。     

Synthesis of Strontium Carbonate by the Induction of Microbiology

Spherical strontium carbonate was synthesized by the induction of microbial bacillus pasteurii at ambient temperature with strontium chloride and urea as the raw materials. The phase composition, particle size and morphology of the product were studied by XRD and SEM. The results indicated that the strontium carbonate synthesized by the induction of microbial bacillus pasteurii was of good dispersion and uniform particle size. The spherical strontium carbonate particles obtained by adding different control agents were constructed by numerous flakes or olive-shaped nano-particles. The products were orthorhombic according to their XRD patterns.     

Synthesis and characterization of poly(methacrylic acid)‐based molecularly imprinted polymer nanoparticles for controlled release of trinitroglycerin

In this study, a novel molecularly imprinted polymer (MIP) based on methacrylic acid (MAA) monomer was synthesized to control release of trinitroglycerin (TNG) as a vasodilator drug for adjusting the cardiac conditions. For this purpose, TNG nanospheres based on poly(methacrylic acid) (PMAA) were prepared by using the precipitation polymerization process. The synthesized TNG nanospheres‐based MIP samples were characterized by means of Fourier transform infrared spectroscopy and field‐emission scanning electron microscopy in order to investigate their provided active functional groups within the cavities as well as morphology, respectively. The results showed that the appropriate non‐covalent bindings between the TNG (template) and PMAA provided within the MIP samples with imprinting factor of 1.98 were achieved by optimizing the amounts of trimethylolpropane trimethacrylate (TRIM) as a cross‐linker and MAA as a functional monomer. On the basis of these obtained conditions, the polymeric nanospheres containing TNG were formed in shape of spherical particles with an average diameter sizing about 40 nm. These remarkable results were obtained by the use of 1:10 molar ratio of TRIM/TNG and 1:6 molar ratio of MAA/TNG. Moreover, in‐vitro release of the TNG from the MIP samples to phosphate buffer solution (pH = 7.4) indicated that the MIP samples had a moderate and gradual release compared with the non‐imprinted polymer samples. These outcomes conducted us to consider the samples as carriers for adjusting potentially cardiac conditions. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrochemically produced responsive hydrogel films: influence of added salt on thickness and morphology

We report on electrochemically prepared hydrogel layers of poly-N-isopropylacrylamide (pNIPAm) and on the influence that the supporting electrolyte has on their thickness and morphology. Ions that are destabilizing in the Hofmeister sense increase the thickness. The effect correlates well with the ion's tendency to lower the lower critical solution temperature (LCST) of pNIPAm films. AFM micrographs show small-scale globules. When the films were produced in the presence of a destabilizing salt (such as ammonium sulfate) one also observes larger features, resembling wrinkles. We attribute the globules to nucleated growth of surface-attached microgels, whereas the wrinkles presumably are produced by the collapse of hydrogen bubbles underneath a well-crosslinked film. Adding a chain transfer agent to the reactant solution reduces the lateral heterogeneities.