Sol-gel reaction in acrylic polymer emulsions: the effect of particle surface charge

Acrylic polymer-silica hybrid emulsions were synthesized from both anionic and cationic polymer emulsions by simple post-addition of tetraethoxysilane as a silica precursor. Solvent resistance of the films from the hybrid emulsions and the zeta-potential of the hybrid emulsions suggested the different forms of silica components in each hybrid emulsion. Thermal gravimetric analysis, 29Si NMR measurements, and transmission electron microscope observations revealed that the hybrid emulsion from the anionic polymer emulsion was a mixture of anionic polymer particles and homogeneously dissolved silicate oligomer-polymer. On the contrary, the hybrid emulsion from cationic polymer emulsion consisted of polymer core-silica shell particles. The electrostatic interaction between the cationic polymer particle surface and the silicate would be responsible for the accumulation of the silicate onto the particle surface, leading to the silica shell layer formation. The sol-gel condensation reaction of silicate in the acidic emulsion phase was revealed to be controllable by the surface charge of the coexisting particles.     

Film formation from monodisperse acrylic latices, part 4: the role of coalescing agents in the film formation process

The role of coalescing agents in the film formation process is studied by means of the turbidity technique, i.e., analysis of light transmission and interference. The basic influence of coalescing agents is (a) lowering the minimum film formation temperature of the latex dispersion, (b) increasing the drying time and (c) improvement of coalescence. Application of coalescing agents also causes a change in polymer particle size as coalescing agents made of TEXANOL (2,2,4 trimethyl-1,3 pentanediol monoisobutyrate) and ethylene glycol monobutyl ether (EB) were used. Turbidity is shown to be a better method to optimize the amount of coalescing agent in a film formation process than the usual brass bar.     

Properties of oil1/water/oil2 double emulsions containing lipophilic acrylic polymer

Stable oil₁/water/oil₂ (o₁/w/o₂) double emulsions (DEs) containing glyceryl monooleate as a promoter of skin permeability in internal ultradispersed phase o1 (heptane) and an acrylic polymer as a pressuresensitive adhesive in external dispersion medium o₂ (ethyl acetate) are obtained. The aqueous interlayer of the DEs contains Tween 80, hydroxypropyl cellulose, and sometimes lysozyme. The phase ratio in the emulsions is constant. The effect of polyacrylate concentration on the stability, microstructure, and rheological properties of DEs is studied. Factors of DE stability, with the viscoelastic properties of the external dispersion medium being of the most importance, are analyzed. The DEs are used to produce ultradisperse films, which exhibit long-term release of lysozyme at a constant rate with its enzymatic activity retained preserved. The diffusion coefficient of the protein in the polymer matrix is determined.     

A multivariate chemometric approach to fluorescence spectroscopy

A multivariate approach to the solution of problems often encountered in the spectrofluorometry of natural samples, utilising information from whole spectra is presented. (a) Piecewise direct standardisation is implemented and employed to transfer emission spectra measured with two different xenon lamps of different ages as if the spectra were measured with the same lamp. (b) It has been shown using a multivariate analysis approach that it is possible to use the raw data points instead of the smoothed data based on an algorithm included in the instrument software by the manufacturer. (c) It is documented that Raman scattering does not hamper the performance of multivariate calibration; on the contrary, in an experiment with sugar samples the concentration prediction errors become about five times lower by including the whole emission spectrum in the analysis instead of using a univariate calibration based on an emission wavelength that only reflects the analyte of interest. (d) An algorithm for variable selection is implemented and employed in the selection of optimal excitation wavelengths. Among 13 emission spectra recorded for a sugar sample at different excitation wavelengths, four of these are chosen that describe 98.51% of the total variance in the original data. (e) Finally the combination of fluorescence spectroscopy and multivariate calibration with conventional chemical data according to the near-infrared black box model is presented. The refined sugar quality parameter, the ash content and the fluorescence emission spectra are correlated by a partial least-squares regression model. Five experiments employing different monochromator slit widths and sugar concentrations are performed, and the best correlation obtained by full cross-validation of the 15 sugar samples is R = 0.98.     

Flow cytometry: a new method to investigate the properties of water-in-oil-in-water emulsions

We present a new and facile method to evaluate w/o/w emulsions containing fluorescent markers by flow cytometry. Flow cytometry allows simultaneous measurement of w/o/w emulsion droplets "marked" with a fluorescent marker or "blank" without the need for complicated sample preparation. The yield of preparation of the w/o/w emulsion and the release rate of the fluorescent marker FITC-BSA were investigated by this new method. The release fraction (after 24 h) of FITC-BSA from the w/o/w emulsion decreased with increasing concentration of FITC-BSA inside the internal phase, just like the release fraction of NaCl as marker from the w/o/w emulsion. Flow cytometry results show that the yield and release behavior in w/o/w emulsions are in agreement with results reported by more complicated methods.     

A novel polymer supported approach to nucleoside modification

Polymer-supported O(6)-(benzotriazol-1-yl)inosine derivatives (Pol-I and Pol-dI) have been synthesized reasonably effectively via reaction of nucleoside phosphonium salts with polymer-linked HOBt (Pol-HOBt). In constast to solution chemistry, use of polymer-supported BOP (Pol-BOP) did not lead to efficient nucleoside loading. Presence of the nucleosides on the support could be readily detected by MAS NMR. Exposure of the polymer-supported nucleosides, Pol-I and Pol-dI, to alcohol, phenol, thiol and amine nucleophiles caused cleavage from the support leading directly to the C-6 modified nucleoside analogues. To our knowledge, these are the first examples of the application of such technology for nucleoside modification. Where possible, results of reactions with the polymer-supported nucleosides are compared to those from solution chemistry, providing insight into the differences between the two techniques. These new polymer-supported nucleosides can be conveniently utilized for diversity-oriented synthesis.     

We the droplets: A constitutional approach to active and self-propelled emulsions

The field of active matter, and particularly active emulsions, is growing rapidly, with significant progress made recently on both theoretical and experimental fronts. Here, we summarize experimental research progress related to active droplets. The constitution of active droplets, in particular the chemical compositions and structure of interfaces, is critical. We discuss how emulsion properties such as mechanism of motion, speed, trajectory, interaction strength, and lifetime are related to the droplet composition. We consider not only traditional single emulsions but also more complex variants, such as Janus droplets, Pickering emulsions, and multiple emulsions. Active behavior of isolated droplets as well as pairwise and multibody interactions between droplets is described. The influence of physical barriers that shape the local chemical gradients and fluid flow is also highlighted. This review provides perspective on the past, current, and promising future experimental research directions in active droplet research.     

A versatile coating approach to fabricate superwetting membranes for separation of water-in-oil emulsions

Separation of oil/water mixtures, especially for the emulsified oil/water mixtures, is important because of the frequent occurrence of oil spill accidents. Utilizing superwetting porous membrane has become a promising approach to separate either surfactant-free or surfactant-stabilized emulsions. Herein we report a facile and versatile strategy for preparing hydrophobic/under-oil superhydrophobic membranes by coating the skeletons of the membranes with the poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) nanoparticles. The obtained membranes could be used to separate various waterin- oil emulsions with high flux and separation efficiency. In addition, owning to the outstanding resistance of PTFPMS to the most organic solvents or oils, the modified membranes exhibited the excellent reusability and the antifouling properties that were critical in the practical applications. Many commercially available membranes can be modified by such a simple method.     

A normoxic acrylic acid polymer gel for dosimetery in radiation therapy

Journal of Radioanalytical and Nuclear Chemistry - A novel low toxic normoxic polymer gel dosimeter containing acrylic acid monomer is prepared and characterized for dosimetry in radiotherapy. Gel...     

The influence of surfactant on the alkali-thickening of acrylic emulsions

Colloid and Polymer Science -     

A theoretical approach to the kinetics of polymer degradation in solution

After main-chain scission in a polymer, the frequency of encounter between segments in the different fragments is related to the separating process between the fragments. The relationship obtained shows that the separating time is proportional to M ^½, where M is the molecular weight, when the excluded volume disappears. When good solvent is used, the half-time for the separation is obtained as τ_½ = const. M ^0.16–0.22, which is approximated to the experimental data obtained previously (τ_½ = const. M ^0.34 and τ_½ = const. M ^0.22) for the degradations of polyisobutene and poly(phenyl vinyl ketone), respectively. The increase of the half-time with increasing coil density can be explained by the excluded volume. The inverse proportionality of the diffusion of segments to solvent viscosity explains the proportionality of the half-time to microviscosity. The above separating process reverses the reaction between polymer radicals. From their dependence on the chain length, τ_½/k_D = const. M ^½ (where k_D is the specific rate for the reaction), is estimated. Such an approximation holds, regardless of the type of solvent.     

Interaction energies of ZnO in acrylic polymer lattices

Water‐based acrylic polymers are frequently used as binders in ceramic materials that contain ZnO as a major component. Thin flexible ceramic films used in semiconductor elements are prepared from ceramic powder, polymer binder, dispergant and plasticizer. In the present work, the chemical reaction of acrylic acid, a part of the polymer, and ceramic powder (ZnO) has been studied by semi‐empirical calculations and Fourier transform infrared spectroscopy (FTIR). Systematic evaluation of model structures using varying contents of acrylic acid showed that ZnO adhesion increases as the carboxylate content in the polymer system increases. Interaction energy surfaces provide a quantitative insight into the spatial distribution of ZnO particles in various model structures. These results are also in good agreement with our infrared spectroscopy measurements.     

A FRET-based approach to ratiometric fluorescence detection of hydrogen peroxide

We report the synthesis, properties, and biological applications of Ratio-Peroxyfluor-1 (RPF1), a new ratiometric fluorescent reporter for hydrogen peroxide. RPF1 is comprised of a two-fluorophore cassette, where the spectral overlap between coumarin donor and fluoran/fluorescein acceptor partners can be controlled by the chemoselective peroxide-mediated deprotection of boronic ester pendants on the acceptor dye. RPF1 features good selectivity for hydrogen peroxide over a variety of reactive oxygen species, including superoxide and nitric oxide, a ca. 8-fold increase in fluorescence intensity ratio (lambda517/lambda464) upon H2O2 reaction, and excitation and emission profiles in the visible region. Experiments with viable yeast mitochondria show that RPF1 can monitor and quantify endogenous production of H2O2, establishing the potential utility of this approach for probing peroxide biology in living systems.     

A proteomic approach to investigate potential biomarkers directed against membrane-associated breast cancer proteins

The identification of specific protein markers for breast cancer would provide the basis for early diagnosis. Particularly, membrane and membrane-associated proteins are rich in targets for antibodies that may constitute suitable biomarkers of carcinogenesis. However, membrane proteins separation using 2-DE remains difficult. In this work, the breast cancer cell line MCF7 was used as source of proteins for the screening of potential cell membrane-associated antigens recognized by autoantibodies in patients with breast cancer and healthy volunteers. The protein extract obtained using trifluoroethanol (TFE) as cosolvent was compared to a total cell lysate protein extract prepared by a current technique. After 2-DE separation of the two extracts, their protein patterns clearly differed. About 63% of the proteins identified in the TFE-extract were predicted to possess at least one transmembrane domain. 2-D blots probed with sera from cancer patients or from healthy volunteers showed that, as expected, additional antigens were provided in the TFE-extract. Thus, the method described here appeared well suited for proteomic investigation of potential biomarkers undetected by current techniques.     

A molecular approach to the spurt effect in polymer melt flow

The Doi-Edwards theory of polymer melts, extended to include relaxation processes associated with chain-length equilibration, is used to make quantitative predictions of a discontinuity in the flow curve of a monodisperse melt in a capillary. A fluid interface between regions of high and low deformation rates is found to propagate from the former into the latter. Our results for the “spurt” and its hysteresis compare favorably with experiment using a molecular weight dependence of the ratio of “reptation time” (T_d) to “equilibration time” (T_eq) in agreement with that determined from nonlinear stress relaxation.     

A new approach to DSC calibration in wax/polymer blending

DSC analysis of wax/polymer blends is carried out between 270 and 420 K. Calibration for melting point and enthalpy is normally carried out using indium (melting point 430 K), which is unsatisfactory for these materials. IUPAC organic standards covering this range tend to sublime and their onset temperatures are variable. Pure alkanes have similar thermal characteristics to wax/polymer blends and some have been well characterised by adiabatic calorimetry. They are being investigated as alternative secondary calibration standards to give more accurate thermal characterisation of wax/polymer blends. Also,n-triacontane can be used to check DSC resolution.     

Film formation from monodisperse acrylic latices 5. Drying and ageing in coalescing agent containing latex films

The influences of drying temperature, ageing time and ageing temperature on the film formation in coalescing agent containing latex films were investigated via turbidity measurements and atomic force microscopy. Coalescing agents used are 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TEX) and ethylene glycol monobutyl ether (EB). Latex films were dried at different temperatures. At a drying temperature of 40 degrees C, the differences in immersion patterns of neat and 1% coalescing agent containing latex films are too small to show significant improvement in film formation during 1 h of drying. Increase of the temperature from 40 to 50 degrees C, however, causes an improvement in film formation. At higher temperatures (95 degrees C), fast removal of the liquid phase cannot be prevented by the addition of 1% coalescing agent. Although addition of higher amounts of coalescing agent results in an increase of particle deformation and film surface smoothness, it intensifies also the water absorption of dried films. Ageing below the MFFT does not result in a significant improvement of film formation in the presence of 1% coalescing agent. Above the MFFT, coalescing agents act more efficiently and cause an improvement in film formation. By addition of higher amounts of coalescing agent the completion of the film formation process is delayed: for example, by the addition of 15% EB, nearly 1 year of ageing at room temperature is required for an efficient result.