Macro–mesoporous silicas complex and the carbon replica

Novel macroporous silicas with ordered mesoporous wall structures (15 nm in pore size) have been synthesized by finely balancing the emulsification of the oil phase with the self-assembly of the amphiphilic block copolymers. The nanocasting method was used to produce hierarchically ordered macro–mesoporous carbon materials. These porous materials have potential applications in catalysis, sorption, separation, etc.     

Effect of Ultrasonication on Droplet Size in Biodiesel Mixtures

Biodiesel fuels have become more attractive recently because of their environmental benefits and cost competitiveness compared to diesel fuel. Many processing improvements have been proposed to increase the conversion rates and the yields of vegetable oil in order to lower production costs and improve biodiesel product quality. In conventional biodiesel production chemistries, alkaline transesterifications of alcohol/oil dispersions should occur primarily near the interface. Ultrasonic mixing has already been shown to increase overall conversion rates for alcohol/vegetable oil mixtures. Our data show that ultrasonic mixing produced smaller droplet sizes than conventional agitation, leading to more interfacial area for the reaction to occur. Droplet size distributions have been measured for conventional impeller and ultrasonic mixing systems using methanol/soybean oil as a model system. The dispersions were stabilized by surfactant in order to obtain droplet size distribution for mixture samples. Ultrasonic mixing produced dispersions with average droplet sizes 42% smaller than those generated using standard impellers.     

Nanostructured latex particles synthesized by nitroxide-mediated controlled/living free-radical polymerization in emulsion

Suspensions of diblock and triblock copolymer particles comprising a poly(n-butyl acrylate) first/central block and polystyrene or poly(methyl methacrylate) second/outer blocks were synthesized by nitroxide-mediated controlled/living free-radical emulsion polymerization. Monofunctional and difunctional alkoxyamines based on the nitroxide SG1 were used as initiators. For the sake of simplicity, sequential monomer additions were performed without any removal of unreacted monomer. Self-assembly of the obtained block copolymers was investigated both under the latex form as well as after different thermal treatments. AFM and TEM analyses revealed the occurrence of “onion-like” lamellar microphases directly inside latex particles for high enough copolymer molar masses and irrespective of molar mass distribution. This particular organization evolved towards more classical block copolymer morphologies upon solvent casting and/or thermal annealing of latex films.     

马来酸酐、甲基丙烯酸羟乙酯共聚物防垢剂的合成及评价

通过实验确定了马来酸酐、甲基丙烯酸羟乙酯共聚物防垢剂的合成条件，并对合成的共聚物进行了性能评价     

乳化液泵曲轴应力的有限元分析

本文利用ANSYS5．7有限元软件,以乳化液泵曲轴为研究对象,对曲轴整体进行有限元分析,提出一种基于整体分析确定多拐曲轴危险相位和基于局部分析确定最大应力危险点的有限元分析方法．继而进行疲劳强度的分析,从而达到优化曲轴结构、提高乳化液泵的设计水平之目的。     

Numerical simulation and experimental study of emulsification in a narrow-gap homogenizer

The present experimental and theoretical study investigates the fragmentation of the oil phase in an emulsion on its passage through a high-pressure, axial-flow homogenizer. The considered homogenizer contains narrow annular gap(s), whereupon the initially coarse oil drops break into fine droplets. The experiments were carried out using either a facility with one or two successive gaps, varying the flow rate and the material properties of the dispersed phase. The measured drop size distributions in the final emulsion clearly illustrated that the flow rate, as well as the dispersed-phase viscosity, and the interfacial tension can significantly affect the drop size after emulsification. The larger mean and maximum drop diameters obtained for the homogenizer with one gap in comparison to those obtained with two gaps (at the same Reynolds number and material parameters of the emulsion phases), highlighted the strong relevance of the flow geometry to the emulsification process. The numerical simulation of the carrier phase flow fields evolving in the investigated homogenizer was proven to be a very reliable method for providing appropriate input to theoretical models for the maximum drop size. The predictions of the applied droplet breakup model using input values from the numerical simulations showed very good agreement with the experimental data. In particular, the effect of the flow geometry—one-gap versus two-gaps design—was captured very well. This effect associated with the geometry is missed completely when using instead the frequently adopted concept of estimating input values from very gross correlations. It was shown that applying such a mainly bulk flow dependent estimate correlation makes the drop size predictions insensitive to the observed difference between the one-gap and the two-gaps cases. This obvious deficit, as well the higher accuracy, strongly favors the present method relying on the numerical simulation of the carrier phase flow.     

Electrochemical synthesis and characterization of novel electrochromic poly (3,4-ethylenedioxythiophene-co-Diclofenac) with surfactants

Copolymers prepared from 3,4-ethylenedioxythiophene (EDOT) and Diclofenac (DCF) through cyclic voltammetric method exhibited electroactive and electrochromic behaviours. Addition of DCF produced bathochromic shift of the EDOT main absorption band from 253.4 to 269.7 nm in the UV-vis spectra. The cyclic voltammetric studies were carried out with different feed concentration of DCF and in the presence of two different surfactants, SDS and CTAB on glassy carbon electrode surface. Effect of scan rate on the three types of electroactive copolymer films was studied. The three different copolymers showed good adherence on the glassy carbon electrode surface in aqueous 0.1 M KCl medium. Spectroelectrochemical analysis of copolymer film was carried out on Indium-Tin-Oxide (ITO) plate and it showed multicolor electrochromic behaviour when the applied potential was changed. The color of the copolymer was changed from neutral yellow to brown and to violet in 0.1 M KCl medium. Among the three different copolymers, the copolymer prepared in presence of CTAB resulted in high contrast colors. The electrochromic parameters such as coloration efficiency, optical contrast, response time and stability were also evaluated. The surface morphology of the copolymer films was characterized by SEM analysis.     

Preparation of planar and oblate particles from emulsion polymerization using polymerizable comb-like branched emulsifiers

This paper presents a method for preparation of planar polymeric microstructures by emulsion polymerization using polymerizable branched emulsifier. Planar, oblate and spherical particles can be prepared by changing the volume and functionality of the hydrophobic tail of the comb-like polymerizable emulsifier, together with altering the monomers. Emulsifiers with bulky tails favored the formation of planar microstructure. The polymerizable emulsifiers were immobilized on the latex particles. Hindered desorption of the emulsifier from the latex improved the latexes' stability and facilitate the formation of planar and oblate particles. The polymerization conversion also depends on the molecular characteristics of the emulsifiers and monomers.     

Synthesis and characterization of poly(1,5-naphthylene vinylene) and its copolymers with poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene)

Poly(1,5-naphthylene vinylene) (PNV) and its copolymers with poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) were synthesized via a liquid-solid two-phase reaction. The liquid phase was a tetrahydrofuran (THF) solution of the monomers, 1,4-bis(bromomethyl)-2-methoxy-5-(2-ethylhexyloxy)benzene (MOEHODCX) and 1,5-bis(bromomethyl) naphthalene (DBMN), and contained a certain amount of tetrabutylammonium bromide (TBAB) as a phase transfer catalyst. The solid phase was potassium hydroxide particles with diameters smaller than 2 mm. The structures of the polymers were studied by infrared and Raman spectroscopies. The solutions of the copolymers emitted green light. The UV-vis and photoluminescence spectral bands of the copolymers showed blue shifts with the increase in their PNV contents. A polymer light-emitting diode was fabricated with the copolymer prepared by copolymerization MOEHODCX and DBMN with feeding molar ratio of 1:1, and its luminescence efficiency was measured to be 0.069.     

Crystallization-driven migration of the low surface energy segment of a copolymer to the bulk

[(BA-C8)₁₈-(6FBA)]_n was synthesized by condensation polymerization of poly(bisphenol A-co-octane) containing 18 repeat units with bromine end groups, (Br-(BA-C8)₁₈-Br), and 4,4′-(hexafluoroisopropylidene)diphenol (6FBA). This copolymer was confirmed to be semicrystalline after a single melting temperature was detected by differential scanning calorimetry. The changes in the surface chemical composition were measured using time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy, the changes in the surface energy were measured using contact angle measurements, and the changes in the surface morphology were detected using atomic force microscopy as the copolymer crystallized. A decrease in the surface fluorine concentration with time was detected because of the movement of the low surface energy units (6FBA) to the bulk during the development of the crystalline phase. This result shows that the decrease in the enthalpy as a result of crystallization overcomes the increase in the surface free energy due to the migration of the low surface energy units to the bulk and the decrease in entropy due to demixing.