Thieno[3,2-b]thiophene as π-bridge at different acceptor systems for electrochromic applications

Benzoselenadiazole, quinoxaline and thieno[3,2-b]thiophene are the units preferred in conducting polymers due to their electrochemical properties. There are no reports in the literature on polymers containing both moieties. In this study, novel benzoselenadiazole, quinoxaline and thieno[3,2-b]thiophene based monomers; 4-(3a,6a-dihydrothieno[3,2-b]thiophen-2-yl)-7-(thieno[3,2-b]thiophenyl)benzo[c][1,2,5]selenadiazole (BSeTT) and 2,3-bis(3,4-bis(decyloxy)phenyl)-5,8-dibromo-2,3-dihydroquinoxaline (QTT) were synthesized via Stille Coupling and polymerized electrochemically. These polymers were characterized in terms of their spectroelectrochemical and electrochemical properties by cyclic voltammetry and UV–Vis–NIR spectroscopy. Spectroelectrochemistry analysis of PBSeTT revealed an electronic transition at 525 nm corresponding to π–π* transition with a band gap of 0.93 eV whereas PQTT revealed electronic transitions at 440 and 600 nm corresponding to π–π* transitions with a band gap of 1.30 eV. Electrochromic investigations showed that PBSeTT has gray color PQTT switching between green and gray. Switching time of the polymers was evaluated by a kinetic study upon measuring the percent transmittance (%T) at the maximum contrast point.     

Terminal defined chain-growth polycondensation of 4-chloropyridine

This work examines the polycondensation of 4-chloropyridine derivatives using an N-(4-tert-butylbenzyl)-4-chloropyridinium (BPymCl) initiator and ion exchange reagents NaBPh₄, NaBF₄, and TBABF₄. The ¹H NMR spectra demonstrate that the product quantity is proportional to the total conversion of the monomer and the initiator. The MALDI-TOF MS spectrum shows that the product contains more than 9 monomer units. The polymerization was well-terminated via the addition of dimethylaminopyridine. These results indicate that the polycondensation proceeds in a chain-growth manner. This polycondensation could be a new example of a controlled polymerization with a well-defined end group.     

Patterning a π-conjugated polyelectrolyte through sequential polymerization of a bifunctional ionic liquid monomer

An electronically conductive polyelectrolyte is prepared by the sequential polymerization of a bifunctional imidazolium-based ionic liquid (IL) monomer, composed of a thienyl and vinyl containing cation paired with a tetrafluoroborate anion. In the first step, potentiodynamic electropolymerization of the thienyl moiety forms a cationic polyalkylthiophene that is soluble in select organic solvents. Cyclic voltammetry (CV) was used to determine the polymer p-doping potential (0.31 V) and the bipolaronic state (1.49 V). The polymer exhibits electrochromism, converting from red in the neutral state (λ_max = 443 nm) to dark blue in the polaronic state (λ_max = 819 nm). The solution-processable polymer can be cast into a film, masked and patterned by UV-initiated free radical polymerization of the vinyl moiety. Small-angle X-ray scattering (SAXS) revealed that the insoluble crosslinked polyalkylthiophene–polyvinylimidazolium adopts a lamellar structure with a lattice spacing of 3.3 nm. Four-probe d.c. conductivity measurements determined the de-doped electrical conductivity was 1.0 × 10⁻² S/cm. The results underscore the importance of the anion in controlling the polymerization of IL monomers.     

Nanostructured poly(3-hexylthiophene-2,5-diyl) films with tunable dimensions through self-assembly with polystyrene

Poly(3-hexylthiophene-2,5-diyl) is among the most widely used conjugated polymers for opto-electronic applications. To enhance its properties, researchers have attempted to nanostructure this polymer using various processes including breath figure arrays, nanolithography and elaborated organic synthesis. We here demonstrate a simple process to nanostructure the conjugated polymer using self-assembly with polystyrene and selective removal of one of the phases. The influence of the molecular weight of each polymer on the thin film morphology was systematically studied by atomic force microscopy. Using this approach, we observe two types of nanostructure, namely, nanoporous and nanoisland structures, of which the dimensions can be tuned by modifying the molecular weight of each polymer in the blend. This simple process introduces a cost-effective alternative to produce thin films of conjugated polymer with average nano-features from 100 nm up to 500 nm which could be used in a wide range of applications.     

聚醚型阳离子聚氨酯聚电解质插层蒙脱土的性能

研究了以阳离子聚氨酯对大分子蒙脱土(MM T)的插层行为,得到了稳定的新型水基聚氨酯纳米复合树脂。插层效果分别用傅立叶变换红外技术(FT-IR)、差热分析(DSC)、热重分析(TGA)和透射电镜(TEM)进行了表征。FT-IR表明纳米MM T粒子与聚氨酯分子间存在物理与化学作用,S i-O键的伸缩振动吸收由1037 cm-1移动到1015 cm-1。由于蒙脱土上的S i-O-H与聚氨酯聚合物上的NH的氢键作用,连接S i原子的羟基的弯曲振动由915 cm-1上移至918 cm-1。透射电镜(TEM)表明阳离子聚氨酯具有较好的插层行为。差热分析(DSC)和TGA的结果显示,纳米片层硅酸盐与聚氨酯的相互作用使聚氨酯的Tsg和热稳定性均呈现大幅度的提高。     

光子晶体编码微球载体的层层自组装稳定

单分散羧基功能化的交联聚甲基丙烯酸甲酯(PMMA)纳米粒子以液滴为模板自组装成三维胶体光子晶体微球,并层层自组装(LBL)包覆上支化的聚乙烯亚胺(PEI)和聚苯乙烯磺酸钠(PSS)高分子聚电解质对,加以戊二醛(GA)交联。制得的三维胶体光子晶体微球结构有序稳定,可用作性能稳定的编码载体。     

TiO2-incorporated polyelectrolyte composite membrane with transformable hydrophilicity/hydrophobicity for nanofiltration separation

The wettability of the membrane surface has shown obvious influent on the separation performance of the membrane. In this work, a hydrophilic PDA-[PDDA/TiO₂]⁺ Cl⁻ membrane was prepared by a one-step codeposition of poly(diallyldimethylammonium chloride) (PDDA) polyelectrolyte solution containing positively charged TiO₂@PDDA nanoparticles with the assistance of dopamine (DA). Such positively charged membrane can be transformed into a hydrophobic membrane PDA-[PDDA/TiO₂]⁺ PFO⁻ via the counterion exchange between Cl⁻ and PFO⁻ (perfluorooctanoate). The transformation between hydrophilicity and hydrophobicity is reversible. For both hydrophilic and hydrophobic membranes, the nanofiltration performances were respectively investigated by the aqueous solution and ethanol solution of dyes including methyl blue (MB), Congo red (CR) and Evans blue (EB), and as well metal salt aqueous solution. The consecutive running stability and anti-fouling performance of both hydrophilic and hydrophobic membranes were explored. The results revealed that both membranes showed high nanofiltration performances for retention of dyes in (non)aqueous solution. For the hydrophilic membrane, the rejection of salts in a sequence is MgSO₄ > Na₂SO₄ > MgCl₂ > NaCl. Moreover, both of the hydrophilic and hydrophobic membranes showed high stability and antifouling property.     

Preparation of conjugated linoleic acid from safflower oil

Synthetically prepared mixtures of conjugated linoleic acid (CLA) are widely used in animal and cell culture studies to investigate the potential effects of the Δ9c, 11t-18:2 isomer found in food products from ruminant animals. Alkali isomerization of linoleic acid is a common method used in the synthesis of a mixture of CLA isomers containing predominantly the Δ9c, 11t-18:2 and Δ10t, 12c-18:2 isomers. Some biological activity might also be mediated by the Δ10t, 12c-18:2 isomer. Currently few published methodologies exist describing procedures for the enrichment of these two isomers. A method is described herein to take advantage of an inexpensive oil, safflower oil, for use in synthesis of CLA and a procedure to enrich the Δ10t, 12c-18:2 isomer.     

有机相中壳聚糖-海藻酸固定化脂酶的特性

研究了壳聚糖 海藻酸固定化脂酶在有机相反应中的稳定性与活性。考察了凝胶时间、壳聚糖浓度及壳聚糖分子质量对固定化脂酶包埋率与活性的影响 ,确定了适宜 pH值与批反应时间。同时讨论了溶剂极性和操作时间对固定化酶稳定性的影响。测定了固定化脂酶水解橄榄油反应的动力学参数。结果表明 ,壳聚糖 海藻酸聚电解质膜可提高固定化酶的包埋率与稳定性     

Supplemental Conjugated Linoleic Acid Consumption Does Not Influence Milk Macronutrient Contents in all Healthy Lactating Women

The term “conjugated linoleic acid” (CLA) refers to a group of positional and geometric isomers that are derived from linoleic acid and are found primarily in meat and milk products from ruminant animals. Due to the array of putative benefits associated with various forms of CLA, there has been recent interest in supplementing human diets with these fatty acids especially when weight loss is desired. However, in many animal models, CLA has been shown to decrease milk fat production. There is some concern, therefore, that maternal CLA supplementation during lactation might inadvertently decrease nutrient supply to the nursing infant. However, there is only limited research on the effect of CLA consumption on milk fat content in women. Based on previously published work from our laboratory, we hypothesized that CLA supplementation would reduce the milk fat percentage in lactating women in a dose-dependent manner. Breastfeeding women (n = 12) were assigned randomly to treatments of 4 g/day safflower oil (SFO), 2 g/day CLA plus 2 g/day SFO, or 4 g/day CLA in a double blind, 3 × 3 Latin square design. Conjugated linoleic acid supplements contained approximately equal amounts of cis9,trans11–18:2 and trans10,cis12–18:2; the two most common isoforms of CLA. Milk was collected by complete breast expression on the last day (day 5) of each intervention period and analyzed for macronutrient and fatty acid composition. On day 4 of each intervention period, infant milk consumption was estimated by 24 h weighing of the infant. Washout periods were 9 days in length. We observed a dose-dependent increase in the concentrations of cis9,trans11–18:2 and trans10,cis12–18:2 in the milk fat. However, we detected neither a change in overall macronutrient composition nor infant milk consumption. These data do not support those obtained from animal models or our previous human work suggesting that consumption of CLA mixtures necessarily reduces milk fat. It is possible that either (1) the interpretation of our previously published data should be reevaluated, and/or (2) there are important intra- and inter-species differences in this regard.