Cationic Latex Particles Research Articles

Cellulose Nanocrystals Mimicking Micron-Sized Fibers to Assess the Deposition of Latex Particles on Cotton

We report the interactions of cationic latex particles synthesized by RAFT/MADIX-mediated emulsion polymerization with anionic cellulose nanocrystals (CNCs) and cotton fabrics. Latexes in the size range 200-300 nm with poly(butyl acrylate) or poly(2-ethylhexyl acrylate) hydropho-bic cores and hydrophilic shell are synthesized. We show that the latex/CNC interaction is me-diated by electrostatics, the interaction being the strongest with the most charged particles. The adsorption process is efficient and does not require any functionalization step for either cellulose or latex. A major result is the observation by cryogenic transmission electron micros-copy of latexes coated with entangled arrays of CNCs, and for the softer particles a notable deformation of their structure into faceted polyhedra. By labeling the latexes with hydrophobic carbocyanine dyes, their deposition on woven cotton fabrics is studied in situ and quantified by fluorescence microscopy. As with the CNCs, the highest deposition on cotton in the wet and dried states is achieved with the most charged latexes. This demonstrates that CNCs can serve as models to adjust the interactions of latex particles with cotton, and thus optimize manufac-turing processes for the development of advanced textiles.

Linking Film Structure and Mechanical Properties in Nanocomposite Films Formed from Dispersions of Cellulose Nanocrystals and Acrylic Latexes.

Cellulose nanocrystals (CNCs) are unique, lightweight materials that possess high elastic modulus and tensile strength, making them of great interest in the formation of nanocomposite materials. However, efficient design of the composite material is essential in translating the mechanical properties of the individual CNCs into the nanocomposite film. In this work, we demonstrate the formation of structured CNC/acrylic dispersions by physical blending of the anionic CNCs with charged acrylic latex particles. By blending with large cationic latex particles, the CNCs adsorbed onto the acrylic latex surface while blending with small latex particles led to the inverse structure. Films were cast from these dispersions and the physical properties were compared with the aim of understanding the influence of the initial structure of the hybrid dispersion on the structure of the final film. A significant difference in the mechanical properties was observed based on the position of the CNCs in the initial dispersion. Adsorption of latex particles onto the CNC surface led to a random distribution of nonconnected CNCs, which contributed little to improving the Young's modulus, while adsorption of CNC onto the latex led to a honeycomb CNC network and a large increase in the Young's modulus. This work underlines the importance of particle structure on the structure and mechanical properties of nanostructured films.

Effect of size of latex particles on the mechanical properties of hydrogels reinforced by latex particles.

Herein, cationic latex particles (CL) of different particle sizes were introduced as a cross-linking center to enhance the mechanical properties of the hydrophobically-associated hydrogels (P(AAm-co-HMA)-CL). Firstly, cationic polymethylmethacrylate (PMMA) latex particles were synthesized via soap-free emulsion polymerization. Subsequently, P(AAm-co-HMA)-CL hydrogels with outstanding mechanical properties were prepared using acrylamide as the monomer, hexadecyl methacrylate as the hydrophobic molecule, and CL as the cross-linking center. The size of CL had a significant effect on the mechanical properties and self-recovery properties of the P(AAm-co-HMA)-CL hydrogels. The hydrogel with larger CL size exhibited low mechanical properties due to weak hydrophobic interactions. In contrast, the hydrogel with small CL size displayed excellent mechanical properties due to an effective entanglement of the hydrophobic chains with the smaller size CL, which significantly affects the mechanical properties of the hydrogel. As a result, the maximum fracture stress and fracture strain of the hydrogel were up to 1.47 MPa and 2847%, respectively. This study can have a profound impact on the development of the technology of toughening hydrogels with latex particles.

Synthesis of Sub-100 nm and Narrow Particle Size Distribution Cationic Latex by One-Step Emulsion Polymerization

A novel approach to synthesize narrow particle size distribution cationic latex particles based on styrene and butyl acrylate was proposed. The effect of monomer/water ratios, surfactant (cetyltrimethylammonium chloride) concentrations, and monomer compositions on the evolution of particle size, distribution, number, and morphology as a function of monomer conversion was concerned in order to confirm the optimum polymerization condition. As expected, the particle size of the ultima latex increased with monomer/water ratios and styrene contents decreased with increasing surfactant concentrations. Continuous nucleation phenomena occurred when monomer/water ratio was lesser than 30/70, resulting in a gradual increase in the number of particles in the whole polymerization process. Combined with the previous work (Colloid and Polymer Science, 2014, 292: 519–525), it was concluded that particle coagulation easily took place in cationic emulsion polymerization of styrene. Thus, the narrow particle size distribution cationic latexes with particle scale between 50 nm and 80 nm, 30 wt% solid content could be prepared in a short reaction time.

A Novel Route to Prepare Cationic Polystyrene Latex Particles with Monodispersity

Relatively clean cation-charged polystyrene (PS) latex particles were prepared via a novel and simple route in the absence of steric stabilizers. The reaction system only included medium, styrene, and initiator with quaternary ammonium moiety. The influences of initiator concentration, and medium composition on the diameter and size distribution of PS latex particles were systematically investigated. The particle morphology and size, the surface N content, and the particle size distribution were respectively determined by SEM, XPS, and laser particle size analyzer. The results indicated that monodisperse and cation-charged PS latex particles with diameter of 0.45–0.95 μm could be successfully produced via the simple reaction system, and cationic initiator concentration played a key role in the preparation of uniform PS latex particles. Finally, a plausible mechanism was proposed for explaining nucleation, growth, and stabilization of PS latex particles.

Aligned cellulose nanocrystals and directed nanoscale deposition of colloidal spheres

Cellulose nanocrystals are aligned in wrinkled polydimethylsiloxane templates and transferred to polyethyleneimine-coated silica surfaces in a printing process similar to microcontact printing. The highly aligned nanorods were deposited onto the surfaces with a line-to-line distance of 225–600 nm without loss of alignment. It was also possible to repeat the transfer process on the same surface at a 90-degree angle to create a network structure. This demonstrates the versatility of the technique and creates more options for advanced multilayering of materials. To demonstrate that the surface properties of the anionic cellulose nanorods were unaffected by the transfer process and to prove the concept of functionalizing transferred particles, cationic latex particles were electrostatically self-assembled onto the cellulose nanorods. The directed deposition of these particles resulted in excellent site specificity and the highest resolution to date for controlled deposition of colloids on an electrostatically patterned surface.

Preparation of Raspberry-Like Nanocomposite Microspheres Based on Soap-Free Cationic Latex and Nano-SiO2 Particles

Raspberry-like nanocomposite microspheres with polymer core and nano-SiO2 particles shell structure were fabricated by a simple mixture process of soap-free cationic poly-styrene-acrylate latex and nano-SiO2 particles. The raspberry-like structured microspheres were formed due to the electrostatic interaction between positive charged cationic latex and negative charged nano-SiO2 particles. Effects of pH on the surface zeta potential of the polymer latex and nano-SiO2 particles were studied. Effect of nano-SiO2 content to the stability of nanocomposite microspheres was investigated. TEM observation shows that when the pH of both the cationic emulsion and nano-SiO2 sol is 3, stable raspberry-like nanocomposite microspheres with 10 wt% nano-SiO2 content can be obtained, the nano-SiO2 particle is distributed on the surface of the nanocomposite microspheres.

Electrophoretic deposition of composite silica/latex particles onto gold substrate and polythiophene-based films

Electrophoretic deposition of raspberry-like particles was carried out onto a gold substrate and polythiophene films. Electropolymerization of thiophenic derivatives was performed on gold electrode using cyclic voltametry in acetonitrile with NBu4PF6 or LiClO4 as the supporting electrolyte. The inorganic/organic raspberry-like particles were silica nanoparticles (20nm diameter) adsorbed on cationic latex particles of submicron size (450nm in diameter). The charge of composite particles was turned positive by the adsorption of cethyltrimethyl ammonium bromide (CTAB). Particle electrophoretic deposition was performed using a specific laminar flow cell. Depending on the type of monomer and the supporting electrolyte, the polymer films exhibit different morphologies and thicknesses. A high surface coverage of the gold substrate by the silica/latex particles was observed. In the case of the gold substrate functionalised with polymer films, particles were mainly deposited around the aggregates of the polymer films.

Preparation and evaluation of C10-cationic latex particle coated open-tubular column for capillary electrochromatography

A simple way was proposed to prepare reverse phase open tubular column (OTC) for capillary electrochromatography (CEC) by dynamically coating cationic latex particles with C10 functional groups onto the fused silica capillary with surface sulphonation. The latex particles are bounded into the capillary wall via electrostatic attraction force and demonstrate good stability under test conditions. Relative bare silica capillary, reverse electroosmotic flow (EOF) is generated for the OTC due to the existence of cationic latex particles onto the capillary. Preliminary separation of aromatic compounds on an OTC with 50 i.d. has been demonstrated.

Polymer particle adsorption at textile/liquid interfaces: a simple approach for a new functionalization route

The adsorption of amino-functionalized poly(methyl methacrylate) particles prepared by emulsion polymerization onto polyamide/elastane fibres was investigated. The influence of several physicochemical parameters (pH, ionic strength) on the colloidal stability and surface properties of the cationic latex particles was first examined. Then, particle adsorption was studied as a function of particle concentration, particle size, time, pH and salinity. The results obtained demonstrated that the adsorption process was mainly governed by electrostatic interactions and the adsorption isotherms were analysed on the basis of a Langmuir model. Finally, the effect of washing steps on the adsorbed particles was investigated. The results obtained indicated strong interactions between particles and textile fibres. Copyright © 2012 Society of Chemical Industry

Enhanced catalytic activity of o-iodosobenzoate in poly[(styrylmethyl)hexadecyldimethylammonium chloride] latexes for the hydrolysis of p-nitrophenyl diphenyl phosphate

Six 5.0 mol% crosslinked poly[(styrylmethyl)hexadecyldimethylammonium chloride] latexes containing 8–67% quaternization were synthesized via two-stage process and used as supports for o-iodosobenzoate (IBA) catalyst in the hydrolysis of model organophosphate compound p-nitrophenyl diphenyl phosphate (PNPDPP). The hydrodynamic diameters of the cationic latexes were less than 200 nm. The rate of the hydrolysis of PNPDPP greatly increased in the presence of the cationic latex particles and strongly depended on the degree of quaternization and amount of the latex as well as pH, type of buffer, and ionic strength of the medium. As the quaternization percentage of the latexes increased, the rates of the hydrolysis increased. The pseudo-first-order and second-order-rate constants of the hydrolysis reaction carried out with different amounts and type of cationic latexes at pH 7.0, 8.0 and 9.0 in different buffer solutions at 25 °C were determined. 1.0 × 10 −5 M IBA in 0.25 mg/mL of QL-67 latex enhanced the rate of the hydrolysis of 1.0 × 10 −5 M PNPDPP about 5670 times in TAPS buffered solution at pH 8.0 compared to the one in buffered solution and 1590 times in the presence of IBA alone in TAPS buffered solution. The highest second-order-rate constant k cat of 21200 ± 1100 M −1 s −1 was obtained when 0.25 mg/mL of QL-67 was employed in the hydrolysis reaction at pH 8.0.

ASSEMBLY PROCESS OF POLYMER NANOPARTICLES AND THEIR CHARACTERIZATION

Preparation of raspberry-like polymer composite particles through adherence of smaller cationic particles of P(St-co-DMHB) (poly(styrene-co-methacryloxyethylhexadecyldimethylammonium bromide)) onto larger PMMA (poly(methyl methacrylate)) anionic particles surface was achieved by heterocoagulation based on electrostatic interaction. A series of P(St-co-DMHB) cationic particles with particle size varied from 43 nm to 105 nm were obtained through emulsion polymerization using different levels of the cationic monomer DMHB. The particles were assembled on the anionic particles surfaces respectively to result in polymer composite particles having different granulations. Light transmittance and particle size and its distribution in the heterocoagulation processes were followed in order to clarify in detail the assembling process of the small cationic polymer particles onto the larger anionic polymer particles. Transmission electron microscope was used to examine the morphologies of the cationic latex particles,the anionic latex particles and that of the composite particles after their heterocoaguculation. It was observed that the degree of coverage of the small cationic particles on the surface of the anionic large particles was adjustable in a range by varying the ratio of the anionic and the cationic latex particles.

Elaboration of hydrophilic aminodextran containing submicron magnetic latex particles

Aminodextran containing submicron magnetic latex particles were prepared in two steps: (a) transformation of oil-in-water magnetic emulsion into structured magnetic latex particles via combination of seed and miniemulsion-like polymerization process and (b) immobilization (adsorption and chemical grafting) of prepared aminodextran onto negatively charged seed magnetic latex particles. The elaborated magnetic latex particles were characterized in terms of particle size, size distribution, morphology, surface charge density, chemical composition, magnetic properties, and also colloidal stability. The results showed that the morphology of the prepared seed magnetic latex is core–shell like and the cationic latex particles are hydrophilic and of high colloidal stability, irrespective of the aminodextran immobilization process.

Study on the interaction between anionic and cationic latex particles and Portland cement

The interaction between organic latex polymers and the surface of hydrating cement was investigated by measuring the zeta potential and adsorbed amount of polymer on cement. First, differently charged model latex particles were synthesized in aqueous media by well-known emulsion polymerization technique. The latex polymers were characterized by differential scanning calorimetry (DSC), dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM). Electrokinetic latex surface properties were investigated by means of streaming potential measurements using a particle charge detector (PCD). It is shown that the anionic latexes adsorb a considerable amount of Ca 2+ from the cement pore solution. Next, adsorption of the latex polymers on the surface of hydrating cement was confirmed by zeta potential measurements using the electroacoustic method. A water to cement ratio in the cement paste as low as 0.5 was studied, representing actual conditions in mortar and concrete. Additionally, adsorption isotherms were determined in a sedimentation test using the depletion method. For all latex polymers, Langmuir type adsorption isotherms were found. The latex dosages required to achieve saturated adsorption on the cement surface obtained from zeta potential measurements correspond well with those determined in the sedimentation test. Electron microscopy photographs confirm that the charged latex polymers adsorb selectively on surface areas of hydrating cement showing opposite charge. This way, domains of organic latex polymers exist on the cement surface. They provide adhesion between the inorganic cement matrix and the organic polymer film formed later on by particle coalescence as a result of cement hydration and drying.

Controlling Porosity within Colloidal Heteroaggregates

Heteroaggregates of cationic poly(2-vinylpyridine) microgels and anionic polystyrene latex particles have been made by mixing dilute, aqueous suspensions. The growth of the heteroaggregates was arrested by the addition of anionic silica particles that adsorbed to the free surface of the cationic microgel particles. The resulting heteroaggregates were then concentrated by vacuum filtration, freeze-dried, and characterized by mercury porosimetry and electron microscopy. The inclusion of soft, deformable microgels resulted in heteroaggregates with higher porosity than obtained with heteroaggregates of anionic and cationic latex particles. Control of the pore volumes within the freeze-dried filter cakes was demonstrated by two approaches. In the first approach, heteroaggregation at a constant KCl concentration of 0.01 mM was arrested at different times after mixing the latex and microgel particles, thereby limiting the size of the aggregates. The porosity of the resulting filter cake increased from 61 to 65 vol % as the aggregation time increased from 15 to 120 s. In the second technique, the aggregation time prior to arrest was maintained at 120 s while the KCl concentration was varied between 0.01 and 10 mM. The pore volume of the aggregates decreased from 65 to 57 vol % as the electrolyte concentration increased, a trend explained in terms of the effect of the Debye length on the aggregation process.

Control of Charge Densities for Cationic Latex Particles

We report a systematic investigation, together with a new method, on controlling cationic charge densities of latex particles. A covalently bonded charge density up to 100 μequiv/g was achieved on the basis of copolymers of glycidyl methacrylate (GMA) and butyl methacrylate (BMA) by either surfactant-free or nonionically stabilized emulsion polymerization, followed by the aminolysis of epoxy groups into quaternary ammonium groups. The cationic charge density was successfully controlled by adjusting the ratio between epoxy and amino groups. It was found that the formation of disadvantageous water-soluble polyelectrolytes was negligible. Cationic charges were also introduced to latex particles by using cationic azo initiators and/or copolymerization with cationic or amine-containing comonomers, but colloidal titrations showed that controlled formation of highly charged cationic latex particles without the formation of water-soluble polyelectrolytes was only achievable for the aminolysis approach.

Latex-Coated Polymeric Monolithic Ion-Exchange Stationary Phases. 1. Anion-Exchange Capillary Electrochromatography and In-Line Sample Preconcentration in Capillary Electrophoresis

A sulfonated methacrylate monolithic polymer has been synthesized inside fused-silica capillaries of diameters 50-533-microm i.d. and coated with 65-nm-diameter fully functionalized quaternary ammonium latex particles (AS18, Dionex Corp.) to form an anion-exchange stationary phase. This stationary phase was used for ion-exchange capillary electrochromatography of inorganic anions in a 75-microm-i.d. capillary with Tris/perchlorate electrolyte and direct UV detection at 195 nm. Seven inorganic anions (bromide, nitrate, iodide, iodate, bromate, thiocyanate, chromate) could be separated over a period of 90 s, and the elution order indicated that both ion exchange and electrophoresis contributed to the separation mechanism. Separation efficiencies of up to 1.66 x 10(5) plates m(-1) were achieved, and the monoliths were stable under pressures of up to 62 MPa. Another latex-coated monolith in a 250-microm-i.d. capillary was used for in-line preconcentration by coupling it to a separation capillary in which the EOF had been reversed using a coating of either a cationic polymer or cationic latex particles. Several capillary volumes of sample were loaded onto the preconcentration monolith, and the analytes (inorganic anions) were then eluted from the monolith with a transient isotachophoretic gradient before being separated by electrophoresis in the separation capillary. Linear calibration curves were obtained for aqueous mixtures of bromide, nitrite, nitrate, and iodide. Recoveries of all analytes except iodide were reduced significantly when the sample matrix contained high levels of chloride. The preconcentration method was applied to the determination of iodide in open ocean water and provided a limit of detection of 75 pM (9.5 ng/L) calculated at a signal-to-noise ratio of 3. The relative standard deviation for migration time and peak area for iodide were 1.1 and 2.7%, respectively (n = 6). Iodide was eluted as an efficient peak, yielding a separation efficiency of 5.13 x 10(7) plates m(-1). This focusing was reproducible for repeated analyses of seawater.

Amino‐functionalized latex particles obtained by a multistep method: Development of a new immunoreagent

AbstractCationic latex particles with surface amino groups were prepared by a multistep batch emulsion polymerization. In the first one, two or three steps, monodisperse cationic latex particles to be used as the seed were synthesized. In the third and fourth steps, the amino‐functionalized monomer aminoethylmethacrylate hydrochloride was used to synthesize the final functionalized latex particles. Three different azo initiators 2,2′‐azobisisobutyramidine dihydrochloride, 2,2′‐azobisdimethylenisobutyramidine dihydrochloride, and 2,2′‐azobisisobutyronitrile were used as initiators. Hexadecyltrimethylammonium bromide was the emulsifier. To characterize the final latices, conversions were obtained gravimetrically, and particle size distributions and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The amount of amino groups was determined by conductimetric titrations. Colloidal aspects were ascertained by measuring the electrophoretic mobilities. Activation of these particles with glutaraldehyde produced an efficient reagent for latex‐enhanced immunoassay. The covalent coupling efficiency (protein covalently bound with respect to the total amount of protein adsorbed) was compressed between 50 and 80%. The developed immunoreagent was applied to the measurement of serum ferritin concentration in a new turbidimetric procedure that was compared with a commercial nephelometric method; the results obtained with both methods demonstrated that the two procedures correlated well (r = 0.992). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2404–2411, 2003

On-column ion-exchange preconcentration of inorganic anions in open tubular capillary electrochromatography with elution using transient-isotachophoretic gradients. 3. Implementation and method development.

A solid-phase extraction method based on an ion-exchange retention mechanism has been used for in-line preconcentration of inorganic anions prior to their separation by capillary electrophoresis (CE). A single capillary containing a preconcentration and a separation zone has been used in a commercial CE instrument without instrumental modification. Analyte anions were retained on a preconcentration zone comprising an adsorbed layer of cationic latex particles, while separation was achieved in a separation zone comprising fused silica modified by adsorption of a cationic polymer. Elution of the adsorbed analytes was achieved using an eluotropic gradient formed by a transient isotachophoretic boundary between a fluoride electrolyte and a naphthalenedisulfonate electrolyte. Optimization of the electrolyte concentrations, sample injection times, and back-flushing times allowed the successful separation of sub-ppb levels of inorganic anions using a 100-min injection at 2 bar pressure, introducing over 40 capillary volumes of sample. A method based on a 10-min injection allowed a 100-fold increase in sensitivity over conventional hydrodynamic injection for Br-, I-, NO3-, CrO4(2-), and MoO4(2-) with a total analysis time of 25 min. Detection limits were dependent on the injection time but were in the range 2.2-11.6 ppb for a 10-min injection time. This approach was used to determine NO3- in Antarctic ice cores where the analysis could be performed using a sample volume 100 times less than that used for ion chromatography.

Synthesis of amino‐functionalized latex particles by a multistep method

AbstractCationic latex particles with surface amino groups were prepared by a multistep batch emulsion polymerization. In the first one or two steps, monodisperse cationic latex particles to be used as the seed were synthesized, and in the third step, two different amino‐functionalized monomers [aminoethylmethacrylate hydrochloride (AEMH) and vinylbenzylamine hydrochloride (VBAH)] were used to synthesize the final functionalized latex particles. 2,2′‐Azobisisobutyramidine dihydrochloride was used as the initiator, and different concentrations of two quaternary ammonium emulsifiers with hydrophobic chains of different lengths were examined. To characterize the final latexes yields were obtained gravimetrically, and particle size distributions and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The amount of amino groups was determined by fluorimetry. The effect of the amino‐functional monomer used on the final latexes and the colloidal behavior of the system were studied. The influence of the different conditions utilized to synthesize the latexes on the colloidal stability of the particles was evaluated in terms of the Fuchs stability ratio and electrophoretic mobility. High yields of the amino‐functional monomers were obtained. Surface amino, amidine, and quaternary ammonium groups provided the cationic character. The colloidal stability behavior of the products obtained was compatible with their cationic character. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2929–2936, 2001