Emulsion polymerisation

The instability of supported liquid membranes has been a major impediment to practical applications. To address this shortcoming, we have developed a method to form semi-permeable polyamide skin layers in situ on supported liquid membranes containing an anion-exchange extractant (trioctylamine) and a neutral extractant (tributyl phosphate). These skin layers encapsulate large extractant molecules within the membranes but allow the transport of small species across the membranes. A liquid±liquid interfacial polymerization reaction was employed to form the polyamide skin layers utilizing monomers that are compatible with the extractants. SEM examination of the membranes shows the polyamide skin layer to be about 1 micron thick with pore sizes below resolution. Membranes with polyamide skin layers showed a typical¯ux of 1 mmol/s m 2 of Cr(VI), about half that exhibited by similar membranes without skin layers. # 1998 Elsevier Science B.V. All rights reserved.

Step and repeat ultraviolet (UV) nanoimprint lithography has advantages such as metal-direct patterning, develop-less process, low line-edgeroughness and easy operation. However, the dirty-template-causing resist pattern peeling and the defect present challenges that must be resolved for mass-produce nano-devices. The approach to use the chemical adhesion by cationic polymerisation between resist material and the photoreactive underlayer during UV irradiation was investigated as the next generation of clean separation technology between template and resist material in step and repeat UV nanoimprint lithography. The obtained chemical adhesion between epoxy groups of the new fluorinated sol-gel silicon-based resist polymer and epoxy groups of novolac-type photoreactive underlayer was achieved with excellent 80 nm patterning dimensional accuracy by replication of imprint process cycles over 32 times, and was one of the key to reduce the resist pattern peeling and defect numbers.

rounded by a polymer shell (1-3). The technique of poly-Polymer encapsulation of small silica particles, using dispermer encapsulation is becoming more and more popular since sion polymerization of styrene in aqueous ethanol medium with polymer-encapsulated particles offer very interesting actual poly(N-vinyl pyrrolidone) (PVP) as stabilizer, is described. Siland potential applications. Encapsulated pigments are inica particles, directly synthesized by the Stö ber process in an volved in the manufacture of cosmetics, inks, and paints to aqueous ethanol medium, are either unreacted (hydrophilic improve the compatibility between the filler and the binder. character) or coated with 3-(trimethoxysilyl) propyl methacry-The process of encapsulation is of particular interest in agrilate (MPS) (hydrophobic character) , which is grafted at the culture and pharmaceutical industries to produce controlledsilica particle surface. When the bare silica particles are used release products such as encapsulated pesticides and drugs as the seed, there is a strong tendency of the silica beads to cover the surface of the polystyrene particles and obviously en-(4). Encapsulation technologies have developed to reduce capsulation does not occur. On the contrary, when the silica toxicity, to mask taste and odor, to facilitate storage or transsurface is made hydrophobic by coating, the inorganic particles port, and to improve the stability of the encapsulated product. are entirely contained in the polystyrene particles as evidenced Polymer-encapsulated inorganic particles may also have inby microscopy techniques (TEM, SEM, AFM). It is shown that teresting properties in areas such as adhesives, textiles, opsome polystyrene chains are then chemically bonded to the silica tics, and electronics (5). particles, through the coupling agent MPS, and that only a small Most methods of encapsulation employ, so far, mechaniamount of bonded polystyrene, compared to the total polystycal processes. Recently, a new encapsulation technology has rene synthesized, is sufficient to obtain encapsulation of the been developed which consists in the coating of fine inorsilica particles with the entire amount of polystyrene syntheganic powders (submicrometer in size) in aqueous system sized during the polymerization. Under our experimental condiby emulsion polymerization. This new polymer-encapsulations, each polystyrene latex particle contains, on average, 4 to 23 silica beads depending, in particular, on the size of the silica. tion process is of particular interest in the paint industry We believe that it is possible to control the composite particle where a uniform distribution of the pigment in the matrix size and morphology by a convenient choice of the composition is required. Latex-encapsulated pigments offer many advanof the system. Moreover, this new polymer-encapsulation protages. The encapsulation of titanium dioxyde with poly cess could be used to synthesize other organic-inorganic com-(methyl methacrylate) has been extensively studied by Caris posite particles, using, for example, other monomers or mineret al. (6-9), who used titanate coupling agents to improve als.

The polymerization of ARB type reversible step growth polymerization in semibatch reactors has been simulated. It is assumed that the condensation byproduct W and the monomer PI both can vaporize, but P, is refluxed back to the reactor. Raoults law as well as Flory-Huggins theory have been used to account for vapor-liquid equilibrium. The degree of polymerization, pn, and the polydispersity index DN have been computed for various situations. The results are found to be most sensitive to the total pressure and the equilibrium constant. A limiting total pressure history Pdt) has been obtained, going below which does not help to increase pn. The final set of equations incorporate both equalities as well as inequalities, and a simple and efficient computational scheme has been suggested to solve them.

This paper describes a modeling and simulation study for the polyurethane synthesis by bulk copolymerization of dicyclohexylmethane 4,4diisocyanate with a mixture of a polyether diol and 1,4-butane diol, in a co-rotating twin-screw extruder. The process model is based on linear chain growth theory, a kinetic expression previously published in literature and the axial dispersion model, in both the hypothesis of non-segregated and totally segregated fluid structures. The numerical simulations evidenced that the effect of segregation phenomenon appears to be significant, particularly in the evaluation of the product polydispersity. Also, the polymerization process features an important sensitivity of the polymer molecular weight in respect to the inlet monomer molar ratio.

The effects of varying the concentrations of cross-linker N, N′-methyelene-bis-acrylamide (BIS) from 2% to 4%, and 2-hydroxyethylacrylate (HEA) monomer from 2% to 4% at 5% gelatin on the dose response of BIS–HEA–gelatin (BHEAG) aqueous polymer gel dosimeters have been studied using magnetic resonance imaging (MRI) for relaxation rate (R2) of water proton. The dosimeters were irradiated with 60Co teletherapy γ-ray

Aluminium complexes bearing the N,N-chelating ligand 1,4-bis(2-hydroxy-3,5-di-tert-butyl)piperazine (1) have been synthesised. Both monometallic and bimetallic aluminium methyl complexes (2 and 3, respectively) were prepared by treatment of 1 with the appropriate amount of AlMe 3. Complex 2 can be converted to 3 by addition of excess AlMe 3. Bimetallic aluminium-ethyl complex 4 was also prepared. Treatment of 1 with AlEt 2 Cl afforded the monometallic chloride complex 5.

This article continues earlier work (Comput. Chem. Eng. 24 (2000) 209) concerning the design and control of isothermal reactorseparator-recycle systems. The multiplicity behaviour of six reaction systems of increasing complexity, from one-reactant, ÿrst-order reaction to chain-growth polymerisation, is investigated. Below a critical value of the plant Damkohler number, Da ¡ Da cr , the only steady state involves inÿnite ow rates. Feasible steady states become possible if the critical value is exceeded, Da ¿ Da cr . For one-reaction systems, one stable steady state is born at a transcritical bifurcation. For consecutive-reaction systems, including polymerisation, a fold bifurcation can lead to two feasible steady states. Moreover, the transcritical bifurcation is destroyed when two reactants are involved. If the gel-e ect is included, a maximum of four steady states are possible. When multiple steady states exist, the achievable conversion is constrained by the instability of the low-conversion branch. This has practical importance for polymerisation systems when the radicals' quasi-steady state assumption is not valid or the gel e ect is signiÿcant. ?

The goal of this research is to investigate the occurrence of covalent grafting of polymer chains onto graphene oxide (GO) sheets during aqueous miniemulsion radical polymerizations of common vinyl monomers. Styrene, benzyl methacrylate and t-butyl methacrylate were polymerized via miniemulsion polymerization using GO as sole surfactant, and the characterisation of GO isolated post-polymerization was investigated by a range of experimental techniques. (Fourier-Transform Near Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Photoelectron spectroscopy (XPS), Raman spectroscopy and X-Ray Diffraction (XRD)). All experimental techniques show consistently that significant grafting occurs for all three monomers under these conditions. Furthermore, Raman spectroscopy indicated that the mechanism of grafting involves the sp 2 carbons present in the GO structure, and not the oxygen-containing functional groups (e.g. epoxy, hydroxyl and carboxyl). The extent of grafting was quantified by XPS, revealing that polymer grafting occurred at levels in the approximate range of 20-60 wt% (grafted polymer relative to the total mass of GO and grafted polymer). Miniemulsion polymerization using GO as surfactant is an attractive approach for synthesis of polymer/GO nanocomposites, and the present results are important in regards to the specific structures and performances of such materials.

A lumped parameter model of an industrial HDPE reactor is presented. Discontinuity in the mode of operation makes either a set of 15 DAEs or a set of 12 DAEs applicable to this system at any instant. The reactor switches back and forth from one model to another reaching a time averaged steady state. The DAEs are integrated by DASSL. Using the Box-Complex procedure, the sum of squares of errors between plant data and model prediction is minimised and the model tuned. The tuned parameters agree with the literature values. Sensitivity analysis of the model shows that manipulation of pressure will yield a faster change in the reactor conditions as compared to manipulating the catalyst feed rate.

Tissue engineering (TE) aims to regenerate critical size defects, which cannot heal naturally, by using highly porous matrices called TE scaffolds made of biocompatible and biodegradable materials. There are various manufacturing techniques commonly used to fabricate TE scaffolds. However, in most cases, they do not provide materials with a highly interconnected pore design. Thus, emulsion templating is a promising and convenient route for the fabrication of matrices with up to 99% porosity and high interconnectivity. These matrices have been used for various application areas for decades. Although this polymer structuring technique is older than TE itself, the use of polymerised internal phase emulsions (PolyHIPEs) in TE is relatively new compared to other scaffold manufacturing techniques. It is likely because it requires a multidisciplinary background including materials science, chemistry and TE although producing emulsion templated scaffolds is practically simple. To date, a number of excellent reviews on emulsion templating have been published by the pioneers in this field in order to explain the chemistry behind this technique and potential areas of use of the emulsion templated structures. This particular review focusses on the key points of how emulsion templated scaffolds can be fabricated for different TE applications. Accordingly, we first explain the basics of emulsion templating and characteristics of PolyHIPE scaffolds. Then, we discuss the role of each ingredient in the emulsion and the impact of the compositional changes and process conditions on the characteristics of PolyHIPEs. Afterward, current fabrication methods of biocompatible PolyHIPE scaffolds and polymerisation routes are detailed, and the functionalisation strategies that can be used to improve the biological activity of PolyHIPE scaffolds are discussed. Finally, the applications of PolyHIPEs on soft and hard TE as well as in vitro models and drug delivery in the literature are summarised.

The effect of thermal treatment of whey proteins (50 g/100 g) at 75, 80, 85, 90 and 95 C before enzymatic treatment with microbial transglutaminase was evaluated by rheological measurements. Thermal denaturation of whey proteins was determined by differential scanning calorimetry (DSC); and the gel point and turbidity were also evaluated after addition of transglutaminase at different pH values in protein solutions. A significant (p < 0.05) interaction was observed between transglutaminase and thermal treatments. At temperatures higher than 85 C the apparent viscosity measurements of whey protein solutions with transglutaminase were significantly higher than those of the control samples. DSC analysis showed that thermal denaturation occurred at temperatures close to 82 C, and the enzymatic reaction was enhanced at higher temperatures. The gel point of whey proteins decreased with transglutaminase addition. This decrease became greater as a function of reaction time due to the formation of high weight protein polymers catalyzed by transglutaminase, which was also observed in the turbidity analysis.

This article describes hybrid materials and systems in which the core integrity of inorganic nanobuilding blocks (NBBs) is preserved and reviews the main synthetic procedures presented in the literature. The relation between the NBB and the resulting hybrid networks is discussed for several striking examples: silicon and tin oxo clusters, polyoxometalates, and transition metal-oxo-based clusters. This approach is extended to nanoparticule-based hybrids. The chemical strategies offered by the coupling of soft chemistry processes and this approach based on functional NBBs allows, through an intelligent and tuned coding, to develop a new vectorial chemistry that is able to direct the assembly of a large variety of structurally well-defined clusters or nanoparticles into complex architectures.

e dei Materiali Wale de1 Risorgimento 4,40136 BOLOGNA (Italy). 1. HISTORICAL BACKGROUND Research into hydrotalcite-like compounds and catalysis followed separate parallel paths up to the year 1970, when the first patent appeared that referred specifically to a hydrotalcite-like strttctum as an optimal precursor for the preparation of hydrogenation catalysts (ref. 1). Hydrotalcite (a mineral that can be easily crushed into a white powder similar to talc, discovered in Sweden around 1842) is a hydroxycarbonate of magnesium and aluminium and occurs in nature in foliated and contorted plates and/or fibrous masses. At the same time that hydrotalcite was discovered, another mixed hydroxycarbonate of magnesium and iron was found, which was called pyroaurite (because of a likeness to gold when heated) and which w,as later recognized to be isostructural with hydrotalcite and other minerals containing different elements, all of which were recognized as having similar features. The fast exact formula for hydrotalcite, [Mg&l2(OH)16CO3.4H20], and of the other isomorphous minerals was presented by E. Manasse, professor of Mineralogy at the University of Florence (Italy), who was also the first to recognize that carbonate ions were essential for this type of structure (ref. 2). The opinion current at that time, which persisted for many years, was that such minerals were mixed hydroxides. On the basis of X-ray investigations, Aminoff and Broome (ref. 3) recognized the existence of two polytypes of hydrotalcite, the first one having rombohedral symmetry and the second having hexagonal symmetry, which was called manasseite in honour of Manasse. It was necessary to wait for Frondel's paper published in 1941 (ref. 4), entitled " Constitution and Polymorphism of the Pyroaurite and Sjisgrenite Groups" before the interrelations between the several minerals and their real constitutions were generally recognized. The confusion and the uncertainty were due to the lack of adequate crystallographic data, which, in turn, was a result of the complex and unusual composition of these minerals as well as of the fact that the papers by Manasse and Aminoff and Broome went unnoticed. In 1942 Feitknecht (mfs. 5,6) synthesized a large number of compounds with a hydrotalcite-like structure, to which he gave the name "doppelschichtstrukturen" (double sheet structures), assigning then the following structure: r 4 M&OH)2 k._.

Mole balance for the molecular weight distribution in homogeneous continuos-flow stirred tank reactors (HCSTRs) for reversible step-growth polymerization has been written. The relation for the moment generating function G is found to be a nonlinear ordinary differential equation and has been solved analytically. The solution of the MWD of the polymer formed is shown to be valid even if the condensation product is removed. At equilibrium, the solution reduces to the Flory distribution. The computations show that the polydispersity of the polymer first increases with the residence time 0 of the reactor, but, for large 0, it reduces to the equilibrium value after undergoing a maximum.

The feasibility of using continuous-flow tubular reactors (CFTR) as an efficient research tool for polymerization reactions is investigated. This is a continuation of the extensive effort that had been made at Dow in recent years to set up and employ an electro-thermal microreactor (an ohmically-heated CFTR), which resulted in several internal and external publications and a US Patent. The main focus of this work is to investigate the effect of operating conditions and flow composition, mainly the number of existing phases, on the molecular weight of the polymer. A series of polymerization experiments were performed in single-phase (liquid) and two-phase (vapor-liquid) flow regimes. In single-phase polymerization, the ethylene concentration falls continuously along the length of the reactor. This will have a significant effect on the kinetics of polymerization, particularly the molecular weight of the produced polymer. A key advantage of operating in the two-phase region is that an almost constant ethylene concentration is maintained along the length of the reactor. In effect, the vapor phase serves as a reservoir that replenishes the ethylene consumed in the liquid phase by polymerization. The molecular weight data show that this assumption is valid provided that the rate of mass transfer is significantly higher than the rate of the polymerization reaction.

Polyhedral oligosilsesquioxane (POSS)-based hybrid polymers have generated much interest nowadays, both from academic and industrial point of view. POSS are completely defined molecules of nanoscale dimensions that may be functionalised with reactive groups suitable for the synthesis of new organic-inorganic hybrids thus providing the opportunity to design and build materials with extremely well defined dimensions possessing nanophase behaviour. POSS have been successfully incorporated into common polymers via copolymerisation, grafting or blending. A variety of POSS-containing copolymers have been prepared and they have portrayed great potential in the development of a wide range of hybrid nanomaterials with diverse properties. This work has critically evaluated the recent developments in syntheses of POSS polymer materials leading to POSS nanocomposites. The syntheses of POSS cages, monomers containing POSS cages, POSS-dendrimers' cores, POSS containing polymers (nanobuilding blocks) and POSS nanocomposites are described in details. This work assesses also the properties of POSS-nanobuilding blocks that can be otherwise used for developing nanocomposites. Such properties include mechanical, thermal, flame retardant and viscoelastic properties. Investigations into POSS-nanobuilding blocks' structure, morphology and compatibility have been reviewed. Other properties covered include ion mobility and swelling characteristics as well as porosity of the POSS-nanobuilding blocks. Lastly, existing and future possible applications are highlighted and final conclusions are drawn.

Raraan spectroscopy is used to study the secondary structure of tubulin in the assembled and the dissociated states from the analysis of the amide-I band. Essentially two states are recognized: the GTP-and the GDP-bound state, differing in a-helix and antiparallel r-sheet content. Microtubules give a spectrum which is very similar to the GDP-bound state. MAV~ and temperature have minor effects, while increasing the pH up to 8 causes a reduction in a-helix content and a increase in antiparallel Ê-sheet. The binding of demecolcine also induces structural changes which are similar to the GDP-bound state.

Polyallylamine films, deposited on Si wafers by radio frequency (RF) pulsed plasma polymerization (PPP), were employed as insulating layers of metalinsulator-semiconductor (MIS) capacitors. The insulating polymer films were deposited at plasma reactor temperatures of 25°C and 100°C. Multiple frequency capacitance-voltage (C-V) measurements indicated that an in-situ heat treatment during film deposition increased the insulator dielectric constant. The dielectric constant, calculated from the C-V data, rose from 3.03 for samples with no heat treatment to 3.55 for samples with an in-situ heat treatment. For both sample sets, the I-V data demonstrates a low leakage current value (Ͻ20 fA) up to 100 V. Capacitance-time (C-t) measurements were also used to characterize the mobile ions in the polymer that migrate over time with applied voltage. Results indicate that the polymer layers contain few electrically active defect centers and virtually no pinholes. Hysteresis in the C-V curves with differing sweep directions was more pronounced for in-situ heat-treated samples indicative of mobile charge.

Three different HNN ?O acyl hydrazones have been prepared and used to make palladium(II) complexes of the type [Pd(NN ?O )Cl]. These have been fully characterised by means of microanalysis, IR and NMR spectroscopy, and mass spectrometry. The isolated complexes catalyse the polymerisation of phenylacetylene in water at room temperature, leading to polyphenylacetylene with high molecular weight. #

Fe(III)-salen complexes encapsulated in the channels of Al-MCM-41 molecular sieves were successfully synthesised in situ by the flexible ligand method. The resulting compound was characterised by XRD, IR spectroscopy, nitrogen adsorption isotherm and 1 H NMR techniques. The loading of complexes in Al-MCM-41 depends on the quantity of framework aluminium, suggesting that there is an electrostatic interaction between the positive charges of the encapsulated Fe(III)-salen complexes and the negative charges of the Al-MCM-41 framework. Polymerisation of bisphenol-A catalysed by Fe(III)-salen-Al-MCM-41 gave 67% conversion; significantly higher than the conventional homogeneous Fe(III)-salen catalyst.

Numerous studies have investigated the ligand-promoted dissolution of Fe (oxyhydr)oxides. In natural environments, inorganic ligands can compete with organic ligands for surface sites on (oxyhydr)oxides which may influence dissolution rates. Published research of this ...

Homogeneous complexes of Ti (IV) bearing sterically hindered bidentate diols such as 1,1-binaphthalene 2,2 diol (Binol) and substituted Binol were prepared and characterized. These catalyst precursors formulated as [Ti(O ∧ O) 2 ] or [Ti(O ∧ O)X 2 ] are found to be active in polymerization of ethylene at high temperatures in combination with alkyl aluminum sesquichloride (Et 3 Al 2 Cl 3) as co-catalyst. The polyethylenes obtained are linear, crystalline and display narrow polydispersities. The unique low molecular weight PE waxes formed in this reaction exhibit properties that have potential applications in surface coating and ink formulations. The influence of various reaction conditions on polymerization is discussed.

The fluorogenic probe N-(1-pyrene)maleimide, MPy, exhibits a fluorescence response directly correlated to the monomer conversion in the radiation-induced polymerisation of methyl methacrylate (MMA). In the low-dose region, the ratio between propagation rate constants for the cross-over reaction in which a MMA radical chain-end reacts with MPy relative to the homopolymerisation reaction of MMA is found to be 1.38 AE 0.15.

This work investigates the effect of potato presence on the degradation of extra virgin olive oil (EVOO) during repeated frying. For this reason the performance of EVOO during frying was compared with its performance during heating at frying temperatures. In order to make meaningful comparisons the temperature profiles obtained during the frying experiments were replicated during the heating experiments by means of a high energy exchange rate cooling ⁄ heating system. The effects of potato-to-oil ratio (1 ⁄ 7 and 1 ⁄ 35 kg potatoes ⁄ L oil) and number (N) of batches (N = 0, 1, 0, 20, 30, 40) were examined. EVOO was analysed using high performance size exclusion chromatography (HPSEC). It was found that polymerisation products increased linearly during frying and heating and that they were not affected by potatoes presence at low ratio. The effect of potato presence became statistically significant (yet not remarkable) at the high ratio. Decomposition products increased during frying whereas they decreased during heating.

We have obtained a new class of porous silica with good structural order and additional corrugated nanopores clustered around the primary mesopores from the co-condensation of TEOS and adamantylphenol-grafted trimethoxysilane (adam-graft SQ) using a triblock Pluronic P123 (EO 20 PO 70 EO 20 , M w ¼ 5800) copolymer as a structure-directing agent. Thermally activated removal of pore-generating moieties (i.e., adamantylphenol groups) in adam-graft SQ involves the generation of secondary micro-to-small mesopores, while the block copolymer template generates 2D-hexagonal mesopores. We found that the mesostructural characteristics and the generation of secondary indented pores right next to the mesopores can be tailored by the addition order of the two silica precursors (TEOS and adam-graft SQ), varying the molar ratio between TEOS and adam-graft SQ in the starting sol mixture, and the degree of silica polymerization. The increase in the hexagonal unit cell parameters is attributed to the increment of pore size originating from the removal of adamantylphenol moieties. It is believed that the hydrophobicity of adamantylphenol groups plays a key role in its selective incorporation into the region near the PPO core blocks and the subsequent generation of corrugated pores along the silica channels resulting in the increase of pore diameter.

Poly(glycidylmethacrylate) was grafted via surface-initiated-atom transfer radical polymerization (SI-ATRP) on a cross-linked acrylate based resin. Epoxy groups of the grafted polymer, were modified into strong cation-exchange groups (i.e., sulfonic groups) in the presence of sodium sulfite. The adsorption of Crystal Violet and Basic Fuchsine on the strong cation-exchange resin was studied under different experimental conditions. The adsorption process for both basic dyes was pH dependent. The maximum adsorption was observed for both dyes between pH 2.0 and 7.0. The maximum adsorption capacity of the cation-exchange resin for CV and BF dyes were found to be 76.8 and 127.0 mg/g, respectively. Adsorption of the dyes on the resin fitted to Langmuir and Temkin isotherm models and followed the pseudosecond-order kinetics. The values of Gibbs free energy of adsorption ( G • ) were found to be −2.92 and −6.31 kJ/mol at 308 K for CV and BF dyes, respectively. These negative values indicated the spontaneity of the adsorption of the dyes on the resin. Desorption of both dyes was achieved from the resin by using 0.1 M HNO 3 and desorption ratio up to 97% was obtained over seven adsorption/desorption cycles.

Molecularly imprinted polymers (MIPs) for 2,4-dichlorophenoxyacetic acid were synthesized via a noncovalent approach with 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as cross-linker in a methanol/water mixture. Templated polymers synthesized in this self-assembly approach rely on complex formation between the target analyte and functional monomers in porogenic solution prior to radical polymerization. Consequently, the achievable selectivity is governed by the nature and stability of these complexes. The nature of noncovalent interactions responsible for complex formation during imprinting of the template 2,4-dichlorophenoxyacetic acid (2,4-D) with the functional monomer 4-vinylpyridine has been investigated. Fourier transform infrared and 1 H NMR spectroscopies provide the fundamental analytical basis for rationalizing the mechanisms of recognition during the imprinting process probing the governing interactions for selective binding site formation at a molecular level. Molecular modeling studies in explicit solvent (chloroform and water) corroborate the importance of hydrogen bonding in aprotic solvents and of hydrophobic interactions in protic media in agreement with the experimental spectroscopic investigations of prepolymerization solutions. Furthermore, chromatographic studies of the synthesized MIPs provided insight on the importance of size, shape, and functionality during selective 2,4-D rebinding processes confirming the results obtained during the prepolymerization studies.

A neural network architecture incorporating time dependency explicitly, proposed recently, for modeling nonlinear nonstationary dynamic systems is further developed in this paper, and three alternate configurations are proposed to represent the dynamics of batch chemical processes. The first configuration consists of L subnets, each having M inputs representing the past samples of process inputs and output; each subnet has a hidden layer with polynomial activation function; the outputs of the hidden layer are combined and acted upon by an explicitly time-dependent modulation function. The outputs of all the subnets are summed to obtain the output prediction. In the second configuration, additional weights are incorporated to obtain a more generalized model. In the third configuration, the subnets are eliminated by incorporating an additional hidden layer consisting of L nodes. Backpropagation learning algorithm is formulated for each of the proposed neural network configuration to determine the weights, the polynomial coefficients, and the modulation function parameters. The modeling capability of the proposed neural network configuration is evaluated by employing it to represent the dynamics of a batch reactor in which a consecutive reaction takes place. The results show that all the three time-varying neural networks configurations are able to represent the batch reactor dynamics accurately, and it is found that the third configuration is exhibiting comparable or better performance over the other two configurations while requiring much smaller number of parameters. The modeling ability of the third configuration is further validated by applying to modeling a semibatch polymerization reactor challenge problem. This paper illustrates that the proposed approach can be applied to represent dynamics of any batch/semibatch process.

Polymers produced by horseradish-peroxidase-catalyzed coupling of phenols have been explored as potential substitutes for phenol-formaldehyde resins. To overcome low substrate solubilities and product molecular weights in water, enzymatic polymerizations in aqueous-organic mixtures have been examined. Peroxidase vigorously polymerizes a number of phenols in mixtures of water with water-miscible solvents such as dioxane, acetone, dimethylformamide, and methyl formate with the solvent content up to 95%. As a result, various phenolic polymers with average molecular weights from 400 to 2.6 x lo4 D were obtained depending on the reaction medium composition and the nature of the phenol. Peroxidase-catalyzed copolymerization of different phenols in 85% dioxane was demonstrated. Poly(pphenylpheno1) and poly(pcresol) were enzymatically prepared on a gram scale. They had much higher melting points, and in addition, poly(p-phenylphenol) was found to have a much higher electrical conductivity than phenol-formaldehyde resins.

A new ATRP initiator, 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid, has been synthesized and grafted as a film on a mechanically polished stainless steel (ASI304) substrate. Molecular integrity of the grafted initiator in the film, alkyl chain ordering, wettability were determined by X-ray photoelectron spectroscopy, infrared, and water contact angles. Polystyrene, poly(methyl methacrylate) and diblock copolymer (polystyrene-b-poly(methyl methacrylate)) brushes have been grafted from the flat stainless steel surfaces through surface-initiated atom transfer radical polymerization (ATRP) and characterized to check the effectiveness of the new initiator for future uses in surface-initiated ATRP.

CH, Figure 7. A close-up of the coiled region between atoms 2 and 3 in Figure 4. depicted in eq 6 which involves the transfer of a hydrogen from atom 2 to atom 1 and the formation of a double bond between atoms 2 and 3. Summary and Conclusions A model based on molecular dynamics was used to investigate the kinetic stability of polymers as a function of temperature, secondary structure, and molecular weight. Temperatures and atomic velocity distributions, as well as the progress of random scission reactions, were monitored as a function of time and were found to be consistent with statistical predictions for these properties. In particular, we observed that the atomic velocities reorganized into Maxwell-Boltzmann distributions almost instantaneously and that the average heat capacities of the model polymers were equal to 2.3 and 2.6 NkB for the coiled and planar zigzag models, respectively. Computer-generated rates of random scission for both planar zigzag and coiled model polymers were found to correlate reasonably well with the functional predictions of RRK theory. The rate constants for random scission of the planar zigzag model polymers, however, were about 4 times as large as the corresponding values for coiled polymers with the same primary structure. The computer simulations indicated further that the thermal stability of individual model polymers increased with decreasing molecular weight but that the rate of degradation per unit mass of sample was independent of the molecular weight distribution of the polymer. Still frames from computer movies of the thermal motions of model polymers have revealed pronounced coilings in the vicinity of dissociating bonds which are consistent with proposed mechanisms for hydrogen transfer. Of particular interest is the observation that the coiling which accompanies bond dissociations in extended chains tends to stabilize the polymer, making further scissions increasingly more difficult. This interplay constitutes a mechanism for self-regulation that may influence mass-loss rates and product distributions in degrading polymers. Acknowledgment. M.N. thanks Dr. Howland Fowler of the Center for Computing and Applied Mathematics (NIST) for providing technical assistance in making the computer movies and Dr. Edmund DiMarzio of the Polymers Division (NIST) for many helpful discussions.

This paper reports the studies made on the vacuum pyrolysis of deashed sugarcane bagasse, on the pyrolysis products. The present work is with an objective to understand the change in the quantity and quality of the oil fraction obtained from pyrolysis, upon pretreatment for deashing of original biomass. Ash, in the entrained char is believed to be catalyzing the polymerization reaction in the oils and thereby increases the viscosity. Three different pre-treatment processes used for deashing are water leaching, mild acid treatment with HCl and mild acid treatment with HF. 1 The study indicates the remarkable influence of pretreatment process for deashing, by enhancing the total energy distribution in oil fraction of the pyrolysis products. This is attributed to selective removal of ash elements along with removal of extractives and hemicellulose in different proportions. However, it was found that the pre-treatments do not improve the stability of oil. The water leachate, as expected, showed potential of making ethanol via fermentation.

This work describes the synthesis of new, environmentally friendly, robust and biocompatible organic–inorganic hybrid materials based on fatty acid methyl ester-functionalised silica. The hydrosilylation reaction was used to covalently anchor 10-...

Evaluation of Vickers hardness of different types of acrylic ... Ana Paula Farina1, Doglas Cecchin2, Rodrigo Gonçalves Soares3, Andre´ Luıs Botelho3, Jessica Mie Ferreira Koyama Takahashi1, Marcelo Oliveira Mazzetto3 and Marcelo Ferraz Mesquita1 1Department of ...

Polyaniline (PANI) dispersion in water has been prepared by using industrially produced and cheaper stabilizer, namely gum acaciadried exudates from a species of acacia tree. Gum acacia stabilized PANI particles can be easily isolated from the aniline polymerization reaction mixture and then re-dispersed in water. By increasing the content of gum acaciain the polyaniline-gum acacia (PANI-ACACIA) redispersable composite from 42 to 70 wt.% it is possible to diminish the average particle diameter from 450 nm to 200 nm and lower its size distribution. The suitability of the dispersion for blending with water-soluble polymers, such as for example poly(vinyl alcohol) (PVA) has also been tested. The composite PANI-ACACIA containing 60 wt.% of gum acacia has yielded the best blends with PVA with the conductivity in the range of 10 − 4 to 10 − 5 S/cm.

The interaction of an olefin with relatively high reactivity toward acid-catalyzed polymerization such as isobutene, with four different solid acids was investigated by means ofin situdiffuse reflectance infrared spectroscopy (DRIFTS), continuous flow studies using a packed-bed oscillating ...

Homogeneous or periodical surface coating of multiwalled carbon nanotubes (MWNTs) can be achieved by in situ polymerization of ethylene as catalyzed directly from the nanotube surfacetreated by a highly active metallocene-based complex, e.g., Cp* 2 ZrCl 2 /methylaluminoxane. This polyethylene (PE) coating allows for the break-up of the native nanotube bundles. Immobilization of methylaluminoxane onto the surface of the carbon nanotubes was evidenced by scanning electron microscopy (SEM) and confirmed by X-ray photoelectron microscopy (XPS) and timeof-flight secondary ion mass spectrometry (TOF-SIMS). The thermal behaviour and degradation were studied by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Transmission electron microscopy (TEM) was used to image polymer-coated MWNTs, showing either a relatively smooth or a textured polymer coating present on the surface of individual, debundled nanotubes, i.e., PE/MWNT nanohybrid ''sausage''-like or ''shish-kebab''-like structures, respectively. It was clearly demonstrated that by modifying the design of the catalytic complexes, it was possible to tune by a reproducible way the morphology of the PE coating around the MWNTs.

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Four different azo dyes were decolorized (color reduction >90%) by bacteria isolated from a textile wastewater effluent. Dye decolorizing was carried out under microaerobic conditions until completion, after which the aromatic amine concentration was determined. A laccase from Myceliophthora thermophila was used to catalyze coupling reactions of the aromatic amines produced from decolorizing the dyes. The reaction was carried out with stirring (100 rpm) in a weak acidic buffer solution (pH 5.0) at 45 • C for 3 days. The presence of aromatic amines in the samples after bacterial decolorizing confirmed the azo bond was reduced in the process. In addition, the UV-vis spectrum was shifted significantly after the sequential bacterial-laccase treatment also indicating a chemical transformation of the dyes. After laccase treatment the solutions formed colored soluble and precipitated products. The particles sizes making up the precipitates formed after laccase treatment varied between 105 and 483 nm as determined by Photon Correlation Spectroscopy (PCS). The laccase treatment also reduced the COD of the dye solutions by ∼20%. We show that successive bacterial-laccase treatment is effective in decolorized azo dyes by reduction of the azo bonds, and promoting coupling reactions between the aromatic amines formed. Promoting coupling reactions between the aromatic amines using enzymes may prove useful for the physical removal and reuse of these amines.