Interfacial physicochemical properties of functionalized conducting polypyrrole particles

Surface-active properties of copolymers of N,N-dimethylacrylamide (DMA) with n-alkylsubstituted acrylamides, namely as n-butylacrylamide (NBA), n-hexylacrylamide (NHA), n-octylacrylamide (NOA), n-dodecylacrylamide (NDA), and their adsorption onto polystyrene (PS) latex particles were studied at 25°C in water. Surface tension lowering (Δγ) at a concentration of 0.1 g dL−1, where adsorption at air-water interface is close to saturation, increased with the content of N-alkylacrylamide units for respective copolymers containing different N-alkylacrylamide units. The dependence was stronger for copolymers with N-alkylacrylamides bearing the higher alkyl group. The amount of adsorption (Ws) onto PS particles at saturation also increased with the content of N-alkylacrylamide units in the copolymers. Ws linearly increased with Δγ for copolymers with NBA and those with lower contents of NHA and NOA which do not form intramolecular hydrophobic microdomains, whereas copolymers of NDA and those with higher contents of NHA and NOA, which form the microdomains, exhibited large Ws but a small increase with Δγ. Ws were lower and also slightly increased with Δγ for polymers of DMA, N-acryloylpyrrolidine (APR) and N-isopropylacrylamide (IPA). It was deduced that the adsorptions of polymers and copolymers used here at air-water and PS particle-water interfaces are mainly governed by their overall hydrophobicity and that of their alkyl groups of n-alkylacrylamide units, respectively.

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.

Three-component interpenetrating polymer networks (IPNs) comprising polyurethane (PUR), poly(n-butyl methacrylate) (PBMA), and polystyrene (PS) latex particles were prepared in a modified one-shot synthesis. The hydroxy-functionlized and unmodified polystyrene latex particles were synthesized via a seeded emulsion polymerization. The incorporation of hydroxyethyl methacrylate into the latex particles was confirmed via diffuse reflectance infrared analysis and modulated-temperature differential scanning calorimetry. The IPNs were characterized by dynamic mechanical thermal analysis, tensile testing, hardness measurements, and transmission electron microscopy. The three-component materials exhibited higher values for the Young's modulus and the Shore A hardness and for the dynamic storage modulus in the higher temperature range from 80 to 140°C than did the PUR/PBMA IPN alone. The latex particles with the hydroxyl functionality exhibited a better miscibility with the microheterogeneous PUR/PBMA IPN than did unfunctionalized PS latex particles, and, therefore, resulted in materials with better damping properties in the temperature range between 80 and 140°C. Transmission electron micrographs confirmed the imporved miscibility of the functionalized latex particles. The latex particles were not, however, dispersed on an individual level but formed agglomerates of between 2 and 20 μm. © 1996 John Wiley & Sons, Inc.

Performance check of particle size standards within and after shelf-life using differential mobility analyzer

Adsorption of polystyrene–poly(4-vinylpyridine) diblock copolymer on the assembled latex film

Singularly narrow size distributions of 200 nm polystyrene latex spheres determined by high resolution mobility analysis

A unique urethane linkage that permits chemical grafting of poly(ethylene oxide) (PEO) linear chains to the surfaces of polystyrene (PS) latex particles has been developed. Chemically grafting the functionalized hydrophilic PEO macromers to the PS particle surface allows the latex to be polymerically stabilized in a water‐based medium. Advantages of the urethane linkage include the high yield of the macromer synthesis and the hydrolytic stability of the final latex. Rheological experiments are used to examine both processing behavior and interparticle interactions for latex systems with different amounts of grafted PEO. Dynamic rheological experiments reveal that, at high macromer concentrations, the grafted PEO layer is effective in shielding the attractive interactions of the core PS particles that lead to flocculation. However, at low macromer concentrations, strong interactions are seen even at low particle weight fractions, indicating the presence of a flocculated system. Steady shear rheological evaluations show that the latex systems possessed suitable flow behavior for coating applications, even at relatively high particle weight fractions. Experimental steady shear data is utilized in conjunction with the Krieger‐Dougherty equation to determine the size of the PEO stabilizing layer. The stabilizing layer thickness decreases as particle concentration increases, indicating a compressible system. Finally, the relationship between the strength of interparticle interactions and PEO graft density is gauged from the dependence of the power‐law exponent of the elastic modulus on particle concentration.

We describe a newly constructed annular-type differential mobility analyzer (DMA) with an effective electrode length of 60 cm, which is longer than that of our original DMA (40 cm length). This long DMA was developed to extend the classification size of particles measuring up to 1.5 μm. As an application of this DMA, the mean diameters and standard deviations were determined for six samples of monodisperse polystyrene latex (PSL) particles ranging from 0.94 to 1.27 μm in nominal diameter. These PSL particles suspended in double-distilled water were aerosolized by a glass nebulizer and then introduced into the DMA. The mean diameters and standard deviations of these PSL particles were calculated by Ehara's method and compared with the nominal diameters and uncertainties. There was good correlation between the nominal diameters of these samples—particularly for recently certified samples—and the measured diameters. Classification of aerosol particles more than 1 micrometer in diameter using this DMA will be useful for many purposes.

The structural change of a filter cake and its effect on permeation flux in crossflow filtration of a suspension containing particles different in size were studied. A suspension containing yeast cells (5 μm in average diameter) and polystyrene latex particles (0.5 μm) with different compositions was used as a model. The change in the structure of the filter cake formed on the membrane surface was observed by using a scanning electron microscope. When the pore size was smaller than the latex particle size, a yeast cell layer containing latex particles was formed on the membrane at the initial stage of filtration. Then, the yeast cell layer was replaced by the latex particle layer. The increase of the circulation flow rate decreased the amount of the filter cake to increase the permeation flux in this case. On the other hand, when the membrane pore size was larger than the latex particle size, a yeast cell layer was first formed on the membrane surface followed by deposition of latex particles on it. The permeation flux was relatively higher than the former case. However, the permeation flux slightly increased with the increase of the circulation flow rate although the weight of the filter cake decreased in the latter case. Thus, a small amount of the latex particles in the cell suspension considerably decreased the permeation flux in crossflow filtration of the suspension. In addition the dependence of the permeation flux on the circulation flow rate was proved to be different whether the small particles were smaller than the membrane pores. These findings including the structure of the filter cakes will be helpful to understand the permeation behaviors in the crossflow filtration of microbial broths which usually contain small particles.

Pickering miniemulsion polymerizations of styrene using octenyl succinic anhydride (OSA) and dodecenyl succinic anhydride (DSA) modified starch nanoparticles (SNP) (~20–25 nm) were conducted. The effect of different degrees of substitution (DS), alkyl chain length, concentration of Pickering emulsifier (PE), and pH was correlated to the shelf‐life stability of the styrene Pickering miniemulsions and the particle size distribution (PSD). Interfacial tension values of aqueous dispersions of SNP‐OSA (DS = 0.11) and SNP‐DSA (DS = 0.14) against toluene as low as 14.7 and 11.0 mN/m, respectively, were observed. Average styrene droplet diameters in the miniemulsions (DV(sty)) ranged between 100–600 nm. 2,2′‐Azobisisobutyronitrile (AIBN) and lauroyl peroxide (LPO) were employed as initiators and the effect of the water solubility on the resulting PSD and latex stability was investigated. The resulting polystyrene (PS) latex particles ranged between 70 and 550 nm in diameter. When AIBN was used as initiator, secondary nucleation was observed. The rate of polymerization and conversion of SNP‐OSA and SNP‐DSA stabilized Pickering miniemulsion polymerizations were compared. The SNP‐armoured PS particles were visualized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). At low conversions (<40%), the resulting latexes were relatively uniform when modified SNP were used as PE along with small amounts of hexadecane as a hydrophobe. At higher conversion, however, coagulation occurred which was correlated to a side reaction in which the PS particles grafted together to form large coagulates.

We report the effect of graphene oxide (GO) on film formation and morphological properties of GO-doped polystyrene (PS) latex nanocomposite (PS latex/GO) films using UV-visible absorption spectroscopy and scanning electron microscopy (SEM). PS latex particles were synthesized through emulsion polymerization technique and then nanocomposite blends, each containing different concentrations of GO ranging from 0 wt% to 70 wt%, were obtained. Prepared blends were deposited on glass plates via drop-casting method, and coated substrates were annealed at different temperatures between 100 °C and 250 °C. At each annealing temperature, transmitted light intensity of nanocomposite films was recorded. Void closure and Prager-Tirrell models were employed to interpret the film formation behavior. Activation energy of viscous flow (ΔH) decreased from 21.80 kcal·mol-1 to 5.91 kcal·mol-1 when the amount of GO content increased in film composition. However, activation energy of interdiffusion (ΔE) varied between 1.08 kcal·mol-1 and 6.94 kcal·mol-1 without any trend upon the addition of GO nanofillers. SEM images of films agreed well with calculated activation energies. Although the interdiffusion process of GO-doped latex films remained unaffected by added GO nanofillers, optical transparency of the films enhanced up to 92.5%, demonstrating that thermally resistant and highly transparent GO-rich nanocomposite films can be fabricated.

Steady state fluorescence (SSF) and photon transmission (PT) techniques were used for studying film formation from TiO 2 and Al 2 O 3 covered polystyrene (PS) latex particles. These films were annealed at elevated temperatures in 10 min time intervals above glass transition (T g ) temperature of polystyrene. Fluorescence emission, I p and transmitted photon, I tr intensities were measured after each annealing step to monitor the stages of film formation. Films present dramatic increase in both I tr and I p above the certain onset temperature called minimum film forming temperature, T 0 . Dissolution of annealed PS film, with high TiO 2 content presented a nice, ordered nano-sized ceramic structure, which may predict the construction of nano-layer photonic crystals. It was observed that latex particles are encapsulated above a critical Al 2 O 3 content of 33 wt% which corresponds to the critical occupation probability of p c =0.33 at which the film obey the site-percolation model with a critical exponent of 0.45.

Impact of processing and storage on citrus fiber functionality: Insights from spectroscopic techniques

This work reports the use of the steady state fluorescence (SSF) technique for studying film formation from TiO2 covered polystyrene (PS) latex particles. The composite films were prepared from pyrene (P)-labeled PS particles by covering them with TiO2 at room temperature and then annealed at elevated temperatures in 10 min time interval above glass transition (T g) temperature of polystyrene. Five different composite films were studied in various TiO2 layer contents. Fluorescence intensities I P from P were measured after each annealing step to monitor the stages of film formation. Films showed considerable increase in I P above the certain onset temperature called minimum film forming temperature, T 0. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 23.12 and 92.80 kJ mol−1, respectively.

In this work, biocompatible and biodegradable chitosan microcapsules are successfully prepared in abundance and easily via using carboxylfunctionalized polystyrene (PS) particles as core template and the chitosan crosslinked with gultaraldehyde as the shell. Firstly, the monodisperse functionalized PS particles are made by emulsifier-free emulsion polymerization. The structure and morphology of the carboxyl-functionalized PS particles are characterized by FTIR, FESEM and TEM. Secondly, microcapsules are accomplished by fabricating on the basis of chemical cross-linking on the surface of the carboxyl-functionalized PS particles and by removing the core template. The microcapsules are characterized by FESEM and TEM. The results revealed that the latex particles are removed by exposure to solvent and the microcapsules exhibited the hollow structure. This work confirmed that the microcapsules are accomplished by fabricating on the basis of chemical cross-linking on the surface of the carboxyl-functionalized PS particles and by removing the core template.