Methacrylic Acid Groups Research Articles

Electrochemically Induced Growth of Zinc Oxide

The electrolytically induced precipitation of zinc oxide from zinc nitrate solution on gold surfaces in the presence of water-soluble polymers was examined for reaction times between 0.5 and 600 seconds. Regardless of the additive, polycrystalline films of zinc oxide have formed after 30 seconds, but polymeric additives dramatically change the morphology of the ZnO films. Amperometric analysis and fitting the diffusion reduced the current density-time curve according to Avrami kinetics and it reveals that polymers bearing methacrylic acid groups result in spherical growth whereas such with sulfonic acid groups lead to a platelike growth of crystallites. Without additive prisms grow predominantly in one dimension. These findings are confirmed also by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis.

Analysis of particle–solvent interactions in pH-responsive cross-linked microgel systems

Viscometry, static light scattering and turbidimetry studies were performed to investigate the interaction between pH-responsive microgels consisting of methacrylic acid (MAA) and ethyl acrylate (EA) copolymers cross-linked with di-allyl phthalate (DAP) and the solvent environment. The characteristics of microgel particles and their corresponding interaction potential were manipulated by varying the following: (a) degree of neutralization of MAA groups; α (b) salt concentrations and (c) microgel cross-linked density. Three independent interaction parameters, i.e. Huggins constant, Kh, second virial coefficient, A2 and apparent second virial coefficient, Bapp, which describe the degree of particle–solvent interactions, were obtained from these techniques. A scaling relationship between the three parameters given as: Bapp/Kh∝αM¯wA2 (where M¯w represents the weight-average molecular weight), was proposed. Good agreement was observed, where all the data for the three different salt concentrations of each microgel with different cross-linked densities collapsed onto a single master curve. This suggested that all three techniques can accurately predict the degree of interaction between microgel particle and solvent environment. Turbidimetry, being the simplest among the three techniques is the most convenient method.

Characterization of Compositional Heterogeneity in Chemically Amplified Photoresist Polymer Thin Films with Infrared Spectroscopy

We demonstrate a general approach to characterize compositional heterogeneity in polymer thin films using Fourier transform infrared (FTIR) spectroscopy. Polymer films with varying degrees of heterogeneity were prepared using a model chemically amplified photoresist where a photoacid catalyzed reaction-diffusion process results in the formation of methacrylic acid (MAA) rich domains. Within these domains, the carboxylic acid groups dimerize through hydrogen bonding. FTIR measurements of the relative fraction of hydrogen-bonded vs free carboxylic groups are used to quantify the degree of compositional heterogeneity. The FTIR data from compositionally homogeneous systems, statistical copolymers, and polymer blends follow the expected linear dependence of the relative hydrogen-bonded fraction with composition. For the chemically amplified photoresist system, the FTIR data deviate substantially from that of the homogeneous distribution. Furthermore, parameters describing the size of the heterogeneity can be determined from a solid sphere model of the deprotected regions catalyzed by the diffusing photoacid. The degree of the spatial heterogeneity varies with changes in the photoacid concentration, reaction conditions, and initial copolymer composition. Increased nonreactive comonomer content decreases the degree of heterogeneity by reducing the hydrogen-bonding efficiency, which is consistent with the dilution of MAA groups.

Swelling behavior and release properties of pH-sensitive hydrogels based on methacrylic derivatives

The purpose of this study is to develop novel intestinal-specific drug delivery systems with pH sensitive swelling and drug release properties. Methacrylic-type polymeric prodrugs were synthesized by free radical copolymerization of methacrylic acid, poly(ethyleneglycol monomethyl ether methacrylate) and a methacrylic derivative of N-(4-hydroxyphenyl)-2-(4-methoxyphenyl) acetamide in the presence of ethylene glycol dimethacrylate as crosslinking agent. The effect of copolymer composition on the swelling behavior and hydrolytic degradation were studied in simulated gastric (SGF, pH 1.2) and intestinal fluids (SIF, pH 7.0). The dynamic swelling behavior of these hydrogels was investigated to determine the mechanism of water transport through these hydrogels. The mechanism of water transport through the gels was significantly affected by the pH of the swelling medium and became more relaxation-controlled in a swelling medium of pH 7.0. The swelling and hydrolytic behaviors of hydrogels were dependent on the content of methacrylic acid (MAA) groups and caused a decrease and increase in gel swelling in SGF and SIF, respectively. Drug release studies showed that the increasing content of MAA in the copolymer enhances hydrolysis in SIF. These results suggest that pH-sensitive systems could be useful for preparation of a muccoadhesive system and controlled release of N-(4-hydroxyphenyl)-2-(4-methoxyphenyl) acetamide.

Self-assembly of acrylic triblock hydrogels by vapor-phase solvent exchange.

We investigate the self-assembly of poly(methyl methacrylate)-poly(methacrylic acid)-poly(methyl methacrylate) triblock copolymers by a vapor-phase solvent-exchange mechanism. Two acrylic triblock copolymers were synthesized with different hydrophilic/hydrophobic block ratios. Hydrogels were formed by exposing the solutions to saturated water vapor. As water diffuses into the solution, the hydrophobic end-blocks form aggregates that are bridged by the hydrophilic mid-blocks. Structure formation in the gels was characterized by small angle X-ray scattering, and swelling was measured in controlled pH buffer solutions. The solvent exchange process occurs while the methacrylic acid group remains in the protonated state. After swelling to equilibrium in water or controlled pH buffers, strong gels are formed with polymer-weight fractions between 0.01 and 0.15, and with shear moduli between 0.6 kPa and 3.5 kPa. Porous gels were produced by adding salt crystals to the polymer solution prior to solvent exchange. Salt was then leached out by immersing the gel into water. Structures of the porous hydrogels were characterized by confocal laser scanning microscopy.

Studies on the porosity of SiO 2-aerogel inverse opals synthesised in supercritical CO 2

A new technique to produce highly porous SiO 2-aerogels inverse opals in supercritical carbon dioxide (scCO 2) is being developed at our laboratory. Polystyrene latex particles decorated with methacrylic acid or a mixture of methacrylic and itaconic acid groups are organized in three-dimensional 3D-latex arrays and used as templates. The polymeric template is reacted with tetraethylorthosilicate (TEOS) or tetramethylorthosilicate (TMOS) dissolved in scCO 2 at 40 °C and 85 bar. The reaction is catalysed by organic acids attached to the latex particle surface. SEM and TEM images show that, upon calcination of the template, highly porous materials replicating the structure of the original template are obtained. N 2-adsorption isotherms reveal the presence of a large porosity located in the macropore wall. In all the cases, the maxima in the pore size distribution appear in the mesopore range. In this paper we investigate ways of controlling the porosity of the material by changing the precursors, the catalyst and/or its concentration. SEM, TEM and N 2-adsorption data show that, at the reaction conditions, reactivity of TEOS and TMOS on the templates is similar, yielding materials of comparable surface area. In the same way, the porosity of the aerogels obtained with templates impregnated using benzosulfonic (BSA) acid and p-toluene sulfonic acid is the same. Lower yields were obtained using monochloroacetic acid. The effect of the catalyst concentration is more important; as the concentration of BSA in the template increases, lower values are obtained for the maximum in the pore size distribution.

Effect of Deprotection Extent on Swelling and Dissolution Regimes of Thin Polymer Films

The response of unentangled polymer thin films to aqueous hydroxide solutions is measured as a function of increasing weakly acidic methacrylic acid comonomer content produced by an in situ reaction-diffusion process. Quartz crystal microbalance with energy dissipation and Fourier transform infrared spectroscopy measurements are used to identify four regimes: (I) nonswelling, (II) quasiequilibrium swelling, (III) swelling coupled with partial film dissolution, and (IV) film dissolution. These regimes result from chemical heterogeneity in local composition of the polymer film. The acid-catalyzed deprotection of a hydrophobic group to the methacrylic acid tends to increase the hydrophilic domain size within the film. This nanoscale structure swells in aqueous base by ionization of the methacrylic acid groups. The swollen film stability, however, is determined by the hydrophobic matrix that can act as physical cross-links to prevent dissolution of the polyelectrolyte chains. These observations challenge current models of photoresist film dissolution that do not include the effects of swelling and partial film dissolution on image quality.

Heteroflocculation of Particle Mixtures by a Coacervation Mechanism. A Rheological Study

In most of the classical studies of heteroflocculation two sets of oppositely charged particles are mixed. In this current study, a somewhat different mechanism of heteroflocculation is described. Two sets of concentrated dispersions of polyacrylate latex particles (having the same surface-charge sign) have been mixed, where the surface of one set had been functionalized with methacrylic acid (MAAc) groups and the second set with poly(ethylene oxide) (PEO) chains. The resultant heteroflocculation has been investigated as a function of the number fraction (F) of MAAc-functionalized particles, the size ratio (R) of the two sets of particles (R = d(MMAc)/d(PEO)), the background electrolyte concentration (0-0.2 M KCl), the pH (3 or 9), and the order of mixing of the particles. The relative extent and strength of flocculation were assessed using two basic rheological techniques: (i) the plastic viscosity (eta(pl)) and the Bingham yield stress (sigmaB) were determined from steady-state shear experiments, (ii) the modulus (G) and the viscosity (eta) (both at a given applied stress) and the actual yield stress (sigmaY) were determined from creep-recovery experiments. Heteroflocculation was observed at a pH value of 3, where the carboxylic groups at the surface of the MAAc-functionalized particles remain largely undissociated. However, no flocculation was observed at pH 9, where the COOH groups dissociate to become COO-. The aggregation mechanism is, therefore, believed to be due to hydrogen-bonding between the hydrogens of the carboxylic acid groups and the ether oxygens present on the surface of the PEO-functionalized particles. To this extent, this mechanism of heteroflocculation resembles the coacervation of mixtures of solutions of two H-bonding polymers, for which aqueous mixtures of PMAAc and PEO (at low pH) are a well-known example. Because both sets of particles carried negative surface charge groups, arising from the polymerization initiator used in their preparation, a minimum concentration of added electrolyte (KCl) was needed before any heteroflocculation between the two sets of particles was observed. However, this minimum KCl concentration for the onset of heteroflocculation was significantly lower than the concentration of KCl required to induce homoflocculation of either set of latex particles separately. At an R value of 1.3, all the rheological parameters passed through a maximum value at F = 0.5, whereas when R was 6.2 the maximum occurred at a value of F = 0.018 or F = 0.025, depending on the order of mixing.

Synthesis and characterization of new cross-linked terpolymer systems containing silyl group

A series of acrylic terpolymers containing silyl pendant groups was prepared by free radical cross-linking copolymerization. Me3Si, Et3Si and t-BuMe2Si together with cubane-1, 4-dicarboxylic acid (CDA) were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The silyl-linked HEMA are abbreviated as TMSiEMA, TESiEMA and TBSiEMA respectively. Cubane-1, 4-dicarboxylic acid (CDA) linked to two HEMA group is the cross-linking agent (CA). Free radical cross-linking terpolymerization of the methyl methacrylate (MMA) and methacrylic acid (MAA) with two different molar ratios of organosilyl monomers and CA was carried out at 60–70 ∘C. The compositions of the cross-linked three-dimensional polymers were determined by FT-IR spectroscopy. The glass transition temperature (Tg) of the network polymers was determined calorimetrically. The Tg of network terpolymers increases with increasing of cross-linking degree. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). The gels swelled more in SIF than in SGF. The swelling behaviour of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in pH 1 or an increase in gel swelling in pH 7.4. Based on the great difference in swelling ratio at pH 1 and 7.4 for P-1, P-6 and P-10 appear to be good candidates for colon-specific drug delivery.

Synthesis and characterization of acrylic type hydrogels containing azo derivatives of 5-amino salicylic acid for colon-specific drug delivery

pH-sensitive hydrogels are suitable candidates for oral delivery of therapeutic peptides, proteins and drugs, due to their ability to respond to environmental pH changes. Terephthalic acid was covalently linked with 2-hydroxyethyl methacrylate (HEMA), abbreviated as cross-linking agent (CA). Acryloyl ester of 5-[4-(hydroxy phenyl) azo] salicylic acid (HPAS) as an azo derivative of 5-amino salicylic acid (5-ASA) was prepared under mild conditions. The HPAS was covalently linked with acryloyl chloride, abbreviated as APAS. Free radical cross-linking copolymerization of polymerizable azo derivative of 5-ASA (APAS) and methacrylic acid (MAA) in two different molar ratios, with the various ratios CA as cross-linking agent were carried out with using 2, 2'-azobisisobutyronitrile (AIBN) as initiator at the temperature range 60-70 degrees C. The composition of the cross-linked three-dimensional polymers was determined by FTIR spectroscopy. Glass transition temperature (Tg) of the network polymers was determined calorimetrically. The hydrolysis of drug-polymer conjugates was carried out in cellophane membrane dialysis bags containing aqueous buffer solutions (pH 7.4 and pH 1) at 37 degrees C. The effect of copolymer composition on the hydrolytic degradation was studied in simulated gastric fluid (SGF, pH 1) and simulated intestinal fluid (SIF, pH 7.4) at 37 degrees C. Monitoring of the hydrolysis process by HPLC and UV spectroscopy shows that the azo prodrug (HPAS) was released by hydrolysis of the ester bond located between the HPAS and the polymer chain. The drug-release profiles indicate that amount drug release dependent on the content of MAA groups and crosslinking.

Using pH‐sensitive hydrogels containing cubane as a crosslinking agent for oral delivery of insulin

The goal of oral insulin delivery devices is to protect the sensitive drug from proteolytic degradation in the stomach and upper portion of the small intestine. Copolymers of 2-hydroxyethyl methacrylate (HEMA) and methacrylic acid (MAA) based hydrogels containing 2, 4, and 6% of a crosslinking agent (CA) were studied as drug delivery systems. Cubane-1, 4-dicarboxylic acid (CDA) was linked to two HEMA groups as CA. Radical copolymerizations of HEMA and MAA with the various ratios of CA were performed at 70 degrees C. The compositions of the crosslinked three-dimensional polymers were determined using Fourier transform infrared spectroscopy. Glass-transition temperature of the network polymers was determined calorimetrically. The effect of copolymer composition on the swelling behavior and hydrolytic degradation was studied in simulated gastric fluid (pH 1) and simulated intestinal fluid (pH 7.4). The swelling and hydrolytic behavior of the copolymers was dependent on the content of MAA groups and caused a decrease in gel swelling in simulated gastric fluid or an increase in gel swelling in simulated intestinal fluid. The drug-release profiles indicate that the amount of drug release depends on their degree of swelling and crosslinking.

Latex produced with carboxylic acid comonomer for waterborne coatings: Particle morphology variations with changing pH

Carboxylic acid comonomers are often added to latex formulations to improve colloidal stability and to help control the physical structure of composite (core-shell type) particles. We have performed a systematic study of the incorporation of methacrylic acid (MAA) within styrene/butyl acrylate copolymer seed latices, and determined the eventual effect on the morphology of the composite particles when using a second-stage monomer that is either polar (MMA) or nonpolar (BMA). These latices have been produced in batch and semibatch reactions in the pH range of 3–7. At low pH, the MAA groups are not ionized, but at the higher pH they may be nearly completely ionized. Here, we report that for batch reactions carried out within the above pH range, the latex particle morphologies of the PMMA second-stage systems change dramatically with increasing pH, while those for the PBMA system do not change at all. These results show that one cannot easily generalize the effect of acid comonomers on the morphology of composite latex particles, as this depends upon the choice of the copolymers in the latex and the process characteristics of the polymerization reaction.

Interpolymer complexes between hydrophobically modified poly(methacrylic acid) and poly( N-vinylpyrrolidone)

The formation and structure of interpolymer complexes between amphiphilic multi-block copolymers—poly(dimethylsiloxane- N-vinylpyrrolidone) and poly(dimethylsiloxane-methacrylic acid)—were studied using potentiometric and conductometric titration, viscometry and fluorescence spectroscopy. The ratio of hydrophobic/hydrophilic groups in the copolymer and the molecular weight of each sequence were varied in order to establish the influence of these parameters on the interactions between the components. The complexation between pairs of block copolymers, of block copolymers and homopolymers as well as between homopolymer pairs was considered. The complexes were formed through the hydrogen bonding. They have a compact structure with a non-stoichiometric composition of pyrrolidone to methacrylic acid groups ratio around 0.6–0.7, with the exception of complexes formed between pairs of homopolymers and of copolymers with the shortest siloxane block. The difference between the new complexes and the ones formed from homopolymers, with equimolar composition, is explained by the spatial non-complementarity of the copolymers having a ‘flower-like’ structure in aqueous solutions.

Chromatographic molecular recognition for catechol-related compounds using thiacalix[4]arene as an effective selector.

Thiacalix[4]arene (5,11,17,23-tetra- tert-butyl-25,26,27,28-tetrahydroxy-2,8,14,20-tetrathiacalix[4]arene) is an amphiphilic molecule comprising four p-tert-butylphenol-like groups ortho-linked by single sulfur atoms. This molecule has a high electron density area owing to the close proximity of the hydroxyl groups and sulfur atoms. We studied the applicability of this interesting compound as a selector for high-performance liquid chromatography (HPLC) thereby presumably exploiting this feature. Firstly, uniformly sized polymer particles were prepared by using a multi-step swelling and polymerization method with ethylene glycol dimethacrylate (EDMA) as a cross-linker. Methacrylic acid (MAA) was introduced onto the surface of the resulting polymer particles through a new modification method. Thiacalix[4]arene was chemically bonded through the MAA group by using 1,4-dibromobutane as a spacer to reduce steric hindrance around the MAA and the polymer particle itself. The performance of the prepared polymer-based thiacalix[4]arene-modified stationary phase was evaluated with HPLC. Specific chromatographic retention behavior was observed for catechol relative to positional isomers of xylene, cresol, and benzene-diol. Catecholamine and catechol showed specific chromatographic retention behavior.

Surface properties of an associative alkali soluble polymer (Acrysol TT-935)

Acrysol TT-935 R&H is an associative alkali soluble polymer with applications to the paper and coating industry. For hydrophobic modified polymers there is a lack of fundamental understanding on their surface properties in aqueous solutions. The aim of this work is to report surface properties of the Acrysol TT-935 obtained from the equilibrium surface tension (EST) (by the du Noüy ring method) within the pH range 5–11 at room temperature and the dynamic surface tension (DST) (by the maximum bubble pressure technique) and the titration curves. From equilibrium surface tension a wide variation in surface activity of the polymer occurred when the pH changed within the range 5–6.5, and it was a function of pH and polymer concentration. This was explained in function of the ionization degree of the methacrylic acid group in the polymer. Also it was shown that critical aggregation concentration and saturation area (cac and Γ s) of the polymer solutions remained constant at different pH within the studied range. The surface properties were obtained using Volmer surface equation of state. Dynamic surface tension experiments were carried out at constant time (1 s) and concentrations beyond the cac in the pH range from 6.5 to 11. From this data, the polymer species were determined as function of pH and changes in the adsorption process were confirmed. The adsorption kinetics at the interface were analysed using a theoretical diffusion model. The polymer solutions showed a pronounced minimum level at pH 6.5 at bulk concentrations greater than 0.60%. This minimum in surface tension occurs at the p K a of the polymer and could be correlated with the change in the activity of the various polymer species in bulk solution and with the fast and strong adsorption and interaction of these species at the interface. The surface properties of the polymer showed how the adsorption process occurred, and the DST gave information about the aggregation mechanism at different pH’s. Characteristics surface tension values over shorter times are also relevant to many industrial applications.

065 Improving Integra™“Take” with Negatively Charged Methacrlylic Acid Beads

Introduction: Integra™ has gained acceptance as a dermal replacement for large burns with limited donor sites. Integra™ vascularization takes between 14 and 21 days. Accelerating the vascularization of Integra™ could improve “take” rates and potentially decrease the obligatory waiting period between application and autografting. Hypothesis: Application of negatively charged methacrylic acid (MAA) beads will enhance vascularization of Integra™ Methods Male Wistar rats (n = 11) had two 2 × 3 cm contra lateral dorsal full thickness wounds excised and grafted using Integra™. The MAA beads were applied under the Integra™ topically on the wound bed. Three experimental treatments were compared: Group 1‐ high‐dose MAA beads, Group 2‐ low‐dose MAA beads, Group 3‐ Integra only. Laser Doppler Imaging (LDI) to assess perfusion, as well as digital photography was done on days 7,10 and 14. Tissue samples for H + E and Factor VIII histological staining were collected on day 14. Results: The average “take” was 99%(p < 0.05) for high‐dose MAA beads, 98%(p < 0.05) for low‐dose MAA beads and 82% in the Integra™ only group at day 7. At day 7 (p < 0.01) and day 10 (p < 0.05), the low‐dose MAA group had significantly greater perfusion than the Integra™ only group. There were no statistically significant differences at day 14. Microvessel density (MVD) counts revealed a >40% increase in the number of vessels in both the low‐dose MAA (p < 0.05) and high‐dose MAA (p < 0.05) groups when compared to the Integra™ only group. There was no difference in LDI perfusion or MVD counts between low and high‐dose MAA groups. Conclusion: Factor VIII staining revealed enhanced angiogenesis in Integra™ treated with low and high‐dose negatively charged MAA beads. Low‐dose negatively charged MAA beads improved and accelerated the vascularization of Integra™ in this rodent model.

Behavior of Poly(N-vinylcaprolactam-co-methacrylic acid) Macromolecules in Aqueous Solution: Interplay between Coulombic and Hydrophobic Interaction

Dynamic light scattering measurements have been performed for aqueous solutions of linear copolymer of N-vinylcaprolactam (VCa) and methacrylic acid (MA) with variable composition (i.e., charge degree of polymer chain). The swelling behavior of macromolecules was investigated as a function of both the solution pH value and fraction of methacrylic acid groups. It was shown that these copolymers are thermosensitive, and intermacromolecular aggregation takes place at the temperature increase. They exhibit compositionally dependent swelling behavior as a function of both pH and temperature. The behavior of studied copolymer was explained by the partial formation of ion pairs. The dependence of hydrodynamic diameter on pH of the solution is nonmonotonic. In acidic media at room temperatures we observed the intermolecular aggregation of copolymers accompanied by a sharp increase of the light scattering intensity. In alkaline media intermacromolecular aggregation is observed at higher temperatures. The effect of oppositely charged surfactant (cationic cetylpyridinium chloride, CPC) on the swelling behavior of PVCa−MA macromolecules was investigated under various conditions of pH and temperature. The association of PVCa−MA macromolecules was demonstrated to be a function of pH and CPC concentration. The equilibrium size of copolymer−CPC aggregates was found. It was shown that the size of intermacromolecular aggregates containing copolymers and CPC depends only weakly on the variation of ambient conditions (pH, surfactant, or copolymer concentration). The effect of temperature on the stability of copolymer/surfactant complexes was studied. This result is compared with recent theoretical predictions.

Light Scattering of Hydrophobically Modified Alkali-Soluble Emulsion (HASE) Polymer: Ionic Strength and Temperature Effects

Novel hydrophobically modified alkali-soluble emulsion (HASE) polymers consisting of methacrylic acid (MAA) and ethyl acrylate (EA) backbone with small amounts of hydrophobic macromonomers grafted to it were synthesized for the present study. The pH, ionic strength as well as temperatures significantly alter the dilute solution properties. At low pH and without the addition of a base, the polymer is water-insoluble and exists as latex. When a base is added, the methacrylic acid groups are neutralized and the polymer solubilizes. The apparent hydrodynamic size increases to a maximum, then decreases to a minimum and thereafter increases to a constant value. With increasing salt concentration, the apparent diffusion coefficients of aggregates and unimers increase and this behavior differs from that of pure polyelectrolyte solutions. Fractal dimensions from intensity light scattering reveal that the structure becomes more compact with increasing salt concentration. A pictorial description of the microstructure at low and high ionic strength is proposed, based on the results of both dynamic and static light scattering. Meanwhile, increasing temperature yields correspondingly higher apparent diffusion coefficients, which can be described by the Arrhenius relationship. However, the reduced diffusion coefficients, fractal dimensions as well as the apparent hydrodynamic sizes are independent of temperature.

Synthesis of Epoxy and Block Oligomer Modified Clay Nanocomposite

ABSTRACTAcrylic triblock (AxMyBz) and diblock (MyBz) oligomers containing methyl methacrylate (MMA, M), methacrylic acid (MAA, A) and dimethylaminoethyl methacrylate (DMAEMA, B) groups are intercalated into the layers of montmorillonite. The results indicate that the block oligomer lay flatly between the clay layers. ICP analyses of Na+ content indicate no unexchanged sodium ions are left in the intercalated clay.Nanocomposites of epoxy and clay modified with block oligomers were synthesized. Glass transition temperature (Tg) of the nanocomposite is 129.6°C (M18B2424+ modified clay) compared to 84.1°C for the physical mixture of epoxy and unmodified clay. Tg increases with decreasing amount of modified clay. When modified clay content are below 2 phr, Tg higher than 131.7 °C can be obtained. Water resistance and light transmittance of the nanocomposite is also improved over composite of epoxy and unmodified clay.

Lead speciation in rainwater samples by modified fused silica capillaries coupled to a direct injection nebulizer (DIN) for sample introduction in ICP-MS

Lead speciation using modified silica capillaries for the introduction of liquid samples to a direct injection nebulizer of an inductively coupled plasma quadrupole mass spectrometer is described and demonstrated. The fused silica capillaries were coated by covalently bonding a cation exchange active organic molecule to the activated capillary surface. The best results were obtained by introducing a bifunctional reagent in a prior step. In this case, a silane reagent was chosen which acted as a methacrylic acid group for further binding. The influence of the chemical modification of the surface of the sample capillary of the DIN on the selective retention of inorganic lead (Pb2+) and triethyllead (Et3Pb+) and hence separation and quantification has been investigated. The strong cation exchanger covering has been tested for its stability over a wide pH range (2–9). The interaction of Et3Pb+ with the strong cation exchanger was negligible while the inorganic lead can be selectively retained at pH > 7. Upon flushing with 10−2 mol L−1 hydrochloric acid, the capillary can be easily regenerated. In order to remove retained inorganic lead several eluents were investigated. Parameters affecting the inorganic and organic lead separation such as sample pH, carrier solution, eluent strength, sample size and flow rate characteristics were studied in addition to optimal DIN-ICP-MS conditions. The detection limits for triethyllead and for inorganic lead were 90 and 200 ng L−1 respectively, i.e., absolute detection limits of 0.3 and 0.6 pg respectively. In order to demonstrate the capability of the technique for the analysis of an environmental matrix, a sample of artificial rainwater was analysed.