Preparation of transparent PMMA/Fe(IO3)3 nanocomposite films from microemulsion polymerization

Polymethyl methacrylate (PMMA)/Fe(IO₃)₃ nanocomposite thin films are obtained by in situ particle generation in microemulsions and subsequent photopolymerization of a mixture containing methyl methacrylate, trimethylolpropane triacrylate, and crystallized iron iodate (Fe(IO₃)₃) nanorods. Hyper‐Rayleigh scattering measurements combined with X‐ray diffraction, transmission electron microscopy, and dynamic light scattering are first used to probe in situ the crystallization kinetics of iron iodate nanorods in water‐in‐oil microemulsions prepared with methyl methacrylate as the oil phase and marlophen NP12 as a surfactant. Trimethylolpropane triacrylate is then added as a crosslinker before spin‐coating. Films are deposited on glass substrates for the nonlinear optical characterizations and on silicon wafers for the piezoelectric and mechanical measurements. Nanocomposite films treated by corona discharge are finally characterized through optical microscopy, laser Doppler vibrometry, and Brillouin spectroscopy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1203‐1211, 2013     

Layered double hydroxide platelets exfoliation into a water‐based polyester

Nitrate layered double hydroxide (LDH) phase Zn₂Al(OH)₆(NO₃)·2H₂O is successfully exfoliated in the presence of polyester under mild conditions using water as essential solvent and at room temperature under air. From small angle X‐ray scattering spectroscopy a total exfoliation is found to be achieved using up to 10 wt % LDH, while intercalated polymer nanocomposite structures largely extended up to 14 nm are observed for loading ranging from 10 to 20 wt %. The process is found to be explained by the diffusion of the polymer chain into the interlayer host structure. Starting from an initial value of 0.89 nm, ≈3, 7, 10, 14, and 20 nm transient interleaved nanostructures are formed without any carbonate uptake. The collective gap distance is certainly due to a defined number of polymer chains diffusing into the LDH interstices. Similarly, starting from an aqueous polyester solution highly concentrated in LDH nitrate phase up to 50% w.w, successive dilutions yield platelet exfoliation, thus rendering a smooth chemistry process attractive for potential applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of chitosan characteristics on coagulation and flocculation of organic suspensions

Several samples of chitosan with different degrees of deacetylation and of different molecular weights were tested for the coagulation–flocculation of organic suspensions. Organic suspensions were prepared by mixing mushroom powder with tap water. Experiments were carried out at pH 5, pH 7, and pH 9. Because decreasing the pH reduced the amount of chitosan required to reach the required turbidity, at pH 9, a high concentration of chitosan was required to achieve the required treatment levels, whereas the difference was less significant between pH 7 and pH 5 (the required concentration of chitosan was halved). Though viscosity, correlated to the molecular weight of chitosan, affected treatment performance, its influence on the efficiency of coagulation–flocculation could be substantially reduced by slightly increasing the concentration of the polymer. This is of importance in the processing of industrial effluents: the aging of a chitosan solution, which may cause partial depolymerization, and loss of viscosity, will have a limited impact on process efficiency. The degree of deacetylation also has a limited effect on treatment performance, especially when the degree of deacetylation exceeds 90%. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2070–2079, 2005     

Films formed from polystyrene latex/clay composites: A fluorescence study

This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (t₃) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (I_s) and fluorescence intensity (I_p) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, I_tr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, T_q, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.     

Determination of the Hansen solubility parameters with a novel optimization method

The Hansen solubility parameters (HSPs) are useful for predicting solvent–solute affinity. In this study, the HSPs and the sphere radii (Ro's) of poly(ether sulfone), bitumen, and lignin were determined by a novel optimization method. A hybrid algorithm, which could locate multiple optima, was developed and used to solve optimization problems for maximizing the fitness (F) and minimizing both Ro and the numbers of good solvent and total outliers. For most selected samples, improved results with higher F and reduced Ro and number of outliers were obtained. The results clarify the correlations among three criteria for an optimal solubility sphere, namely, the smallest Ro, highest F, and lowest number of outliers. They can be satisfied simultaneously only when outliers are avoided; otherwise, a reduction in Ro decreases F but can retain the same outliers. Thereby, defining the solubility sphere as the one having the smallest Ro and the lowest number of outliers is more reasonable according to the physical significance in both cases. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43328.     

Preparation of raspberry‐like poly(methyl methacrylate) particles by seeded dispersion polymerization

The facile preparation of nonspherical raspberry‐like poly(methyl methacrylate) (PMMA) particles by seeded dispersion polymerization of methyl methacrylate (MMA) on micron‐sized PMMA seed particles was described. Various polymerization parameters influencing the particle morphology, as well as the polymerization kinetic and morphological stability, were investigated in detail. It was found that the following polymerization conditions were necessary to prepare this kind of nonspherical particles: a relatively low temperature, an appropriate ratio of seed/MMA, an initiator with a relatively low decomposition rate, and a relatively low initiator concentration. These particles showed very good morphological stability at room temperature, but they changed to the spherical ones when heat treated at 60°C in methanol solution of MMA. The experimental results suggest that the prepared PMMA particles were kinetically favored and the localized polymerization of the MMA monomer on PMMA seed particle surface was responsible for the formation of the raspberry‐like particles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Continuous emulsion polymerization of vinyl acetate. II Operation in a single Couette–Taylor vortex flow reactor using sodium lauryl sulfate as emulsifier

Continuous emulsion polymerizations of vinyl acetate were conducted at 50°C in a single continuous Couette–Taylor vortex flow reactor (CCTVFR) using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator. The polymerization can be carried out very smoothly and stably, but the steady‐state monomer conversion attained in a CCTVFR is not as high as that in a plug flow reactor (PFR), but only slightly higher than that in a continuous stirred tank reactor (CSTR), even if the Taylor number is adjusted to an optimum value. Also, the effects of operating variables, such as the emulsifier, initiator, and monomer concentrations in the feed and the mean residence time on the kinetic behaviors were almost the same as those observed in a CSTR. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2755–2762, 2002     

Fouling Control by Reduction of Submicron Particles in a BF‐MBR with an Integrated Flocculation Zone in the Membrane Reactor

Abstract

Submicron particles represent one of the major foulants in the biofilm membrane reactor BF‐MBR. Reduction of the amount of submicron particles (colloids) adjacent to the membrane is one measure in order to provide better fouling control in BF‐MBR systems. A submerged hollow fiber (Zenon Zeeweed) membrane reactor was redesigned by introducing a flocculation zone below the aeration device of the membrane module. This resulted in reduction of submicron particles around the membrane from 8.2% to 6.9%, expressed in differential number percentage. The size of the most abundant particle fraction consequently increased from 0.70 to 0.84 µm. Furthermore, the modified membrane reactor design provided longer operational cycles, >40% reduction of suspended solids around the membrane, and improved retentate/concentrate characteristics, i.e., dewaterability (CST), settleability (SVI/SSV) and filterability (TTF).     

Bilayer-mediated assembly of cationic nanoparticles adsorbed to lipid bilayers: Insights from molecular simulations

Understanding interactions between functionalized gold nanoparticles (NPs) and lipid bilayers is essential for biomedical applications. Experiments have shown that NPs that are stable in solution can assemble into clusters when adsorbed to a lipid bilayer, suggesting that bilayer-mediated interactions facilitate assembly. In this work, we use coarse-grained molecular dynamics simulations to study bilayer-mediated interactions between NPs adsorbed to single- and multicomponent lipid bilayers. We perform unbiased simulations and umbrella sampling calculations using an implicit solvent force field to determine the thermodynamic contributions to assembly. We show that bilayer-mediated interactions drive the assembly of NPs into linear aggregates on liquid-disordered bilayers, which we attribute to a reduction in bilayer curvature. Similar bilayer-mediated interactions induce the alignment of NP clusters with phase boundaries in phase-separated bilayers. Together, these simulation results provide new physical insight into the balance of forces that dictate the assembly of charged NPs at multicomponent lipid bilayer interfaces.     

Electrokinetic and antibacterial properties of needle like‐TiO2/polyrhodanine core/shell hybrid nanostructures

The aim of this study was to fabricate needle like‐TiO₂/polyrhodanine nanostructures by polymerizing rhodanine monomer on the TiO₂ nanoparticles' surfaces and investigate their antibacterial activities. The structural, thermal, morphological, surface and electrical properties of non‐covalently functionalized nanoparticles were characterized by using FTIR, XPS, elemental analysis, TGA, XRD, SEM‐EDX, TEM, contact angle, and conductivity measurements. Characterization results confirmed the formation of needle like‐TiO₂/polyrhodanine (PRh) core/shell hybrid nanostructures. Alterations on the surface and electrokinetic properties of the materials were characterized by zeta (ζ)‐potential measurements with the presence of various salts and surfactants. The ζ‐potential of needle like‐TiO₂ was observed to increase from ?7.6 mV to +28.4 mV after forming a core/shell needle like‐TiO₂/PRh nanocomposite structure and with the presence of cetyltrimethyl ammonium bromide (CTAB) surfactant. Thereby colloidally more stable dispersions were formed. Antibacterial properties of needle like‐TiO₂/PRh were also tested against Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli by various methods and they showed good antibacterial activity. The highest killing efficiency was determined for needle like‐TiO₂/PRh against E. coli by colony‐counting method as 0.95. TEM experiments also showed the immobilizations of the nanoparticles on E. coli and revealed the interactions between E. coli and the nanoparticles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41554.