Synthesis and characterization of cleavable surfactants derived from poly(ethylene glycol) monomethyl ether

A series of noncyclic acetal-linked cleavable surfactants were simply prepared by condensation of aldehydes with poly(ethylene glycol) monomethyl ethers. All of the products were characterized by¹H nuclear magnetic resonance. Their hydrophile-lipophile balance, surface tension, cloud point, critical micelle concentration, and foam height were determined. Hydrolysis kinetic studies, followed by gas chromatography, showed that they had higher hydrolytic reactivity in acidic solution than cyclic acetal-linked cleavable surfactants.     

Reduction of NO2 stored in a commercial lean NO x trap at low temperatures

Isothermal storage of NO₂ and subsequent reduction with different reducing agents (H₂, CO or H₂ + CO) in a lean NO _x trap catalyst was tested by Temperature Programmed Desorption (TPD) and Temperature Programmed Reduction (TPR) experiments at temperatures representative of automotive “cold-start” conditions (<200 °C) using a commercial NO _x trap catalyst. Results from the TPR experiments revealed that no reduction of stored NO₂ to N₂ was observed at 100–180 °C, and at 200 °C 10% reduction only of NO₂ to N₂ was measured. A special affinity of H₂ to form NH₃ was observed during the reduction of stored NO₂. The formation of NH₃ increases with increasing amount of stored NO₂ and decreases with increasing storage temperature. Direct relation exists between the amount of adsorbed and/or stored NO₂ and the formation of H₂O and NH₃.     

Rubber‐toughened polypropylene nanocomposite: Effect of polyethylene octene copolymer on mechanical properties and phase morphology

Rubber‐toughened polypropylene (PP)/org‐Montmorillonite (org‐MMT) nanocomposite with polyethylene octene (POE) copolymer were compounded in a twin‐screw extruder at 230°C and injection‐molded. The POE used had 25 wt % 1‐octene content and the weight fraction of POE in the blend was varied in the range of 0–20 wt %. X‐ray diffraction analysis (XRD) revealed that an intercalation org‐MMT silicate layer structure was formed in rubber‐toughened polypropylene nanocomposites (RTPPNC). Izod impact measurements indicated that the addition of POE led to a significant improvement in the impact strength of the RTPPNC, from 6.2 kJ/m² in untoughened PP nanocomposites to 17.8 kJ/m² in RTPPNC containing 20 wt % POE. This shows that the POE elastomer was very effective in converting brittle PP nanocomposites into tough nanocomposites. However, the Young's modulus, tensile strength, flexural modulus, and flexural strength of the blends decreased with respect to the PP nanocomposites, as the weight fraction of POE was increased to 20 wt %. Scanning electron microscopy (SEM) was used for the investigation of the phase morphology and rubber particles size. SEM study revealed a two‐phase morphology where POE, as droplets was dispersed finely and uniformly in the PP matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3441–3450, 2006     

甲醇吹除气中氢的回收方法

对目前甲醇吹除气中氢回收的两种方法进行了比较、分析。     

2，6－双（5－硝基－2－糠叉）环己酮的制备

用５－硝基糠叉二醋酸酯与环己酮在６０％Ｈ３ＰＯ４溶液中缩合制得标题物。反应混合物在１００℃下搅拌反应５ｈ得６１％的２，６－双（５－硝基－２－糠叉）环己酮。分别经ＩＲ、１ＨＮＭＲ、ＭＳ、ＵＶ、ＴＬＣ和元素分析进行了表征和鉴定。     

Synthesis,degradation, and drug delivery of cycloaliphatic poly(ester anhydride)s

The high melting point of poly(1,4‐cyclohexanedicarboxylic anhydride) [poly(CHDA)] is a disadvantage, in that it is intractable in the melting process of a drug delivery system. This report relates to diols introduced into the polyanhydride main chain to decrease its melting point. Various poly(ester anhydride)s containing ethylene glycol, 1,3‐propanediol, 1,4‐butanediol, or 1,6‐hexandiol [poly(CHDA–XDO)] were synthesized by the esterification reaction and melt polycondensation. FTIR, DSC, WAXD, and intrinsic viscosity of polymers were recorded and hydrolytic degradation, as well as in vitro drug delivery, was conducted. The results show that the samples are stable in an anhydrous environment at room temperature and degrade in water following a surface erosion mechanism. The degradation period of poly(CHDA–XDO) ranged from 130 to 320 h as a result of the different diols and amounts of XDO introduced. The in vitro drug delivery gave 130–350 h of stable delivery along with the typical surface erosion mechanism. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2509–2514, 2002     

A generalist herbivore in a specialist mode Metabolic,sequestrative, and defensive consequences

Adults of a generalist herbivore, the lubber grasshopper,Romalea guttata, can be converted to functional specialists by feeding them exclusively on catnip,Nepeta cataria. No obvious adverse effects on adult development resulted from this enforced monophagy. Notwithstanding the fact thatR. guttata has had no coevolutionary relationship with this Eurasian mint, it readily sequesters compounds that are identical to or derived from the terpenoid lactones that are characteristic ofN. cataria. R. guttata appears to both biomagnify minor allelochemicals and to sequester metabolites of theNepeta terpenes in its paired defensive glands. The levels of autogenously produced phenolics are not affected by feeding onN. cataria and the defensive secretions of catnip-fed grasshoppers are more repellent to ants than those of wild-fed acridids. Metabolites of theN. cataria monoterpenes are sequestered in the defensive glands when catnip is added to the natural diet ofR. guttata. The ability of a generalist,R. guttata, to facilely bioaccumulate a potpourri of foreign allelochemicals when feeding in a specialist mode is analyzed in terms of its biochemical, physiological, and functional significance. Sequestration is examined as a response to the enteric effronteries represented by the phytochemicals that can be characteristic of the overload in a monophagous diet.     

Characterization of ramie yarn treated with sodium hydroxide and crosslinked by 1,2,3,4‐butanetetracarboxylic acid

Ramie yarns were treated with various concentrations of NaOH at room temperature and subsequently crosslinked with 1,2,3,4‐butanetetracarboxylic acid (BTCA). The microstructure and tensile properties of the treated yarns were characterized. X‐ray diffraction (XRD) and FTIR were used to study the crystalline structure of the resultant ramie yarns. The results showed that the maximum change in the structure of the alkali‐modified ramie took place at 16% NaOH, which would completely transform cellulose I to cellulose II. At the same time, the crystallinity index and fiber orientation decreased to the minimum value while the absorption properties were enhanced. The average degree of polymerization (DP ) of the treated ramie yarns slightly decreased after NaOH treatment. Tensile properties including tenacity, breaking elongation, and modulus of the treated yarns were also investigated. Scanning electron microscopy (SEM) was used to investigate the breakage of the treated yarns. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1857–1864, 2004     

Evaluation of the thermal and mechanical properties of poly(ε‐caprolactone), low‐density polyethylene,and their blends

The thermal and mechanical properties of low‐density polyethylene (LDPE), poly(ε‐caprolactone) (PCL), and their blends were evaluated. Differential scanning calorimetry showed that increasing the PCL content of the blend did not change the LDPE melting temperature, but reduced the crystallinity by up to 16.8%. This behavior was related to interactions between the PCL chains and the crystalline phase of LDPE. Tensile strength and elongation at break values for the blends were lower than those for the pure polymers, which suggested an incompatibility between the polymers. The values for Young's modulus under tensile increased when PCL was added to LDPE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3909–3914, 2004     

Surface morphology and nodule formation mechanism of cellulose acetate membranes by atomic force microscopy

By the use of atomic force microscopy (AFM), formation mechanism of nodular structure in cellulose acetate membranes was systematically investigated. Elementary factors affecting the nodule formation were delineated on the basis of both kinetic and thermodynamic considerations. It was shown that (1) the exact nature of nodular structure is thermodynamic equilibrium glassy state; nodular structure will vanish in the rubbery state; (2) the thermodynamic factor affecting nodule formation is the membrane formation temperature; with the membrane formation temperature decreasing, more chain segments are able to form nodular structures; (3) nodule formation is dependent on the segment rearrangement; variation of the solvent environment is the major kinetic factor affecting the segment rearrangement and nodule formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1328–1335, 2003