Reversible controlled assembly of thermosensitive polymer-coated gold nanoparticles

Aggregation of thermosensitive polymer-coated gold nanoparticles was performed in aqueous solution in the presence of a triblock copolymer poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic P123, PEO(20)-PPO(68)-PEO(20)). The gold nanoparticles, AuNPs, which are covered by thermosensitive statistical copolymers poly(EO(x)-st-PO(y)), aggregate when the temperature is higher than the phase transition temperature of the polymer, leading to a macroscopic precipitation. The presence of Pluronic chains in solution prevents the uncontrolled aggregation of the AuNPs at higher temperature than both the aggregation temperature of the AuNPs (T(agg)) and the critical micellization temperature (cmt) of the Pluronic. The size, the colloidal stability, and the optical properties of the AuNPs aggregates are modulated as a function of the P123-to-AuNP ratio, which constitutes the critical parameter of the system. Moreover, the AuNP aggregation is totally reversible upon decreasing the temperature below T(agg). Our approach constitutes an easy way to the formation of well-controlled nanoparticle aggregates with well-defined sizes. The resulting aggregates have been characterized by UV-vis spectroscopy, dynamic light scattering, and electron microscopy.     

Rheo-optical properties of silicone oil emulsions in the presence of polymer emulsifiers

Oil in water emulsions prepared by dispersion of silicone oils into an aqueous solution of hydroxylpropyl methyl cellulose (HPMC) or poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers were characterized by measurements of steady-state shear viscosities, dynamic moduli, and stress-strain sweep curves coupled with optical microscopic observation. The emulsions prepared with HPMC showed solidlike viscoelastic responses and a clear yield stress, whereas the emulsions emulsified by PEO-PPO-PEO block copolymers indicated liquidlike viscoelastic behavior. The difference should be attributed to stronger protective colloidal effects, that is, the former emulsifiers form a more viscoelastic polymer layer adsorbed on the oil droplets than the latter ones. Moreover, the simultaneous optical microscopic observation showed that the emulsions stabilized by HPMC do not flow below the yield stress and beyond the yield stress the movements of oil droplets occur first.     

Aggregation behavior of polypropylene oxide with electric charges at both ends in aqueous solution

The aggregation behavior of polypropylene oxide (PPO) with positive charges at both ends was investigated in aqueous solution by means of the measurements of solution turbidity, dynamic light-scattering, differential scanning calorimetry, and dye solubilization. The positive charges were produced by protonation of terminal NH(2) groups attached to the polymer composed of 33 PO units. It was found that the aggregation behavior is quite sensitive to temperature. At low temperature, the polymer dissolves in water as a unimer. When temperature is increased, the unimer solution undergoes a phase separation to give a turbid solution. Further increase in temperature produces a transparent micellar solution. The aggregation of the polymer molecules must be induced by the dehydration of PPO chain caused by temperature increase. According to the analysis of heat absorptions associated with the melting of the solid mixture and the phase separation of the unimer solution, it is suggested that approximately 10% dehydration of PPO chain causes the phase separation. The temperature-composition phase diagram of aqueous mixture of this polymer was constructed on the basis of turbidity and DSC experiments, which reveals the aggregation behavior of this polymer in aqueous medium as a function of concentration and temperature.     

Ionic effects on the behavior of thermoresponsive PEO–PNIPAAm block copolymers

The temperature‐dependent aggregation and recovery of the copolymer poly(ethylene oxide)₂₂‐b‐poly(N‐isopropylacrylamide)₂₉ with a C₁₂ end‐cap in aqueous solutions of salts and acids are investigated. Salt solutions affected the critical aggregation temperature of the copolymer in a manner predictable according to the Hofmeister series, with the kosmotropic adipic ion lowering the critical aggregation temperature and the chaotropic iodide raising it. Also, both salts and acids increased the size of copolymer aggregates formed with heating, due to the electrostatic shielding of aggregated structures provided by the electrolytes. Additionally, the presence of ionic additives caused a thermohysteretic increase in the size of copolymer aggregates with temperature cycling. The transitions of polymer structure with increasing temperature were surprisingly sharp with the C₁₂ end‐cap present, and particularly broad in samples in which the end cap had been cleaved. This observation suggested that the hydrophobic end group was responsible for imparting some degree of order to the polymer at low temperatures, which allowed for rapid reconfiguration with increasing temperature. Finally, in addition to the transitions expected from the least critical solution temperature behavior of the polymer blocks, we have observed an unexpected additional transition which we attribute to the contraction of the poly(ethylene oxide) chains of the copolymer aggregates at higher temperatures. This work illustrates the importance of considering the environment and composition of thermoresponsive block copolymers in certain applications, particularly in solutions with even modest electrolyte concentrations (1–10 mM), as it can have a profound effect on transition temperatures and morphology. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 507–516     

Temperature-responsive phase transition of polymer vesicles: real-time morphology observation and molecular mechanism

Novel thermosensitive polymer vesicles with controlled temperature-responsive phase transition at the lower critical solution temperature (LCST) varying from 8 to 81 degrees C were prepared via self-assembly of amphiphilic hyperbranched star copolymers having a hydrophobic hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO) core and many hydrophilic polyethylene oxide (PEO) arms. Real-time optical microscopic observation revealed that the polymer vesicles have undergone sequential morphology changes including enrichment, aggregation, fusion, and vesicle-to-membrane transformation near the LCST. Molecular-level investigation indicates that the LCST transition results from the decreasing water solubility of the polymer vesicles with increasing temperature based on the partial dehydration of the PEO vesicle corona. On the basis of these results, a LCST transition mechanism, in view of the molecular configuration, balance of hydrophilic and hydrophobic moieties, and the vesicle morphology transformations, was proposed. As far as we know, the work presented here is the first demonstration of thermosensitive vesicles based on PEO, and the finding may be useful to design the thermosensitive core-shell structures by introducing the PEO segments.     

正离子型疏水改性聚氧乙烯单成相组分双水相系统的相行为

对正离子型疏水改性聚氧乙烯(HM-EO)单成相组分双水相系统的相行为进行了考察,并分析其电荷特性.HM-EO在水溶液中呈现两亲性,可以形成胶束,进而形成带电的胶束簇集体.通过改变溶液的pH值、盐浓度及添加带相反电荷的表面活性剂SDS,可改变胶束簇集体的带电状态,从而影响系统的相行为.增大pH值,有利于系统的分相.盐的添加也可以增大双水相两相区域,正离子影响次序为K+>Na+,负离子次序为SO42->F->Cl->Br->I-.进一步考察了HM-EO和SDS之间的相互作用,结果表明SDS能与HM-EO形成混合胶束簇集体,改变HM-EO双水相系统的带电特性.     

Stability Characteristics of Dispersed Oil Droplets Prepared by the Microchannel Emulsification Method

A novel emulsification method, microchannel (MC) emulsification, was developed for making monodispersed regular-sized droplets in our laboratory. An oil-in-water dispersed system, in which phosphate buffer was used as the continuous phase, sodium dodecyl sulfate (SDS) as the surfactant, and clove oil as the dispersed phase, was prepared by this technique. The average diameter of oil droplets was about 20 μm, with a narrow size distribution. The stability characteristics of the dispersed oil droplets were investigated by an optical microscope and kinetic light scattering method. The stability of the dispersed oil droplets depended on the SDS concentration. When the SDS concentration was above the critical micelle concentration (CMC), the turbidity of the dispersed solution sharply increased at the initial stage. Optical microscopic observation has confirmed that a part of the oil droplets broke up with time, and submicrometer droplets appeared. On the other hand, when the SDS concentration was below the CMC, the turbidity of the dispersed solution had little change in the initial stage, showing that the oil droplets were very stable. The effect of ion concentration was also examined. The results showed that the stability of the oil droplets depended on the balance of the Van der Waals attraction and electrical repulsion between the oil droplets in low ion concentration. Copyright 2001 Academic Press.     

丙烯酰胺在聚乙二醇水溶液中聚合产品的微观形态

采用偶氮类水溶性引发剂2,2′-偶氮二异丙基咪唑啉二盐酸盐(VA044)引发丙烯酰胺(AM)在聚乙二醇(PEG)水溶液中的双水相聚合;研究了引发剂、单体、聚乙二醇浓度及温度对最终产品中聚丙烯酰胺(PAM)液滴形态、尺寸的影响.随着引发剂浓度的增加,液滴由球状变为细长条状;随着温度的上升,球状液滴逐渐趋于条状,然后又重新趋于球状;在初始单体浓度较低时,PAM液滴滴径分布较窄,当其浓度增加后,滴径呈多峰分布;随着PEG浓度的增加,聚合物液滴趋于球状。     

Small-angle neutron scattering study of temperature-induced emulsion gelation: the role of sticky microgel particles

In this work, small-angle neutron scattering (SANS) is used to probe the structural transformations that accompany temperature-induced gelation of emulsions stabilized by a temperature-responsive polymer. The latter is poly(NIPAM-co-PEGMa) (N-isopropylacrylamide and poly(ethyleneglycol) methacrylate) and contains 86 mol% NIPAM. Turbidity measurements revealed that poly(NIPAM-co-PEGMa) has a lower critical solution temperature (T(LCST)) of 36.5 degrees C in D(2)O. Aqueous polymer solutions were used to prepare perfluorodecalin-in-water emulsions (average droplet size of 6.9 mum). These emulsions formed gels at 50 degrees C. SANS measurements were performed on the poly(NIPAM-co-PEGMa) solutions and emulsions as a function of temperature. The emulsion was also prepared using a D2O/H2O mixture containing 72 vol% D2O in order to make scattering from the droplets negligible (on-contrast). The SANS data were analyzed using a combination of Porod and Ornstein-Zernike form factors. The results showed that the correlation length (xi) of the polymer scaled as xi approximately phi(p)(-0.68) at 32 degrees C, where phi(p) is the polymer volume fraction. The xi value increased for all systems as the temperature increased, which was attributed to a spinodal transition. At temperatures greater than T(LCST), the polymer solution changed to a polymer dispersion of poly(NIPAM-co-PEGMa) aggregates. The aggregates have features that are similar to microgel particles. The average size of these particles was estimated as 160-170 nm. The particles are "sticky" and are gel-forming. The on-contrast experiments performed using the emulsion indicated that the interfacial polymer chains condensed to give a relatively thick polymer layer at the perfluorodecalin-water interface at 50 degrees C. The gelled emulsions appear to consist of perfluorodecalin droplets with an encapsulating layer of collapsed polymer to which sticky microgel particles are adsorbed. The latter act as a "glue" between coated droplets in the emulsion gel.     

Oil-continuous microemulsions mixed with an amphiphilic graft copolymer or with the parent homopolymer Polymer–droplet interactions as revealed by phase behavior and light scattering

Polymer–droplet interactions have been studied in AOT/water/isooctane oil-continuous microemulsions mixed with an amphiphilic graft copolymer, or with the parent homopolymer (AOT = sodium bis(2-ethylhexyl) sulfosuccinate). The graft copolymer has an oil-soluble poly(dodecyl methacrylate) backbone and water-soluble poly(ethylene glycol) side chains. Pseudo-ternary polymer/droplet/isooctane phase diagrams have been established for both the parent homopolymer and the graft copolymer, and the two types of mixture display entirely different phase behavior. The homopolymer–droplet interaction is repulsive, and a segregative phase separation occurs at high droplet concentrations. By contrast, the graft copolymer–droplet interaction is attractive: the polymer is insoluble in the pure oil, but dissolves in the microemulsion. A comparatively high concentration of droplets is required to solubilize even small amounts of polymer. Static and dynamic light scattering has been performed in order to obtain information on structure and dynamics in the two types of mixture. For optically matched microemulsions, with a vanishing excess polarizability of the droplets, the polymer dominates the intensity of scattered light. The absolute intensity of scattered light increases as phase separation is approached owing to large-scale concentration fluctuations. Dynamic light scattering shows two populations of diffusion coefficients; one population originates from “free” microemulsion droplets and the other from the polymer (for homopolymer mixtures) or from polymer–droplet aggregates (for mixtures with the graft copolymer). The graft copolymer forms large polymer–droplet aggregates with a broad size distribution, which coexist with a significant fraction of free droplets.     

Physical properties of aqueous solutions of a thermo-responsive neutral copolymer and an anionic surfactant: turbidity and small-angle neutron scattering studies

Aqueous mixtures of the anionic sodium dodecyl sulfate (SDS) surfactant and thermo-responsive poly(N-vinylcaprolactam) chains grafted with omega-methoxy poly(ethylene oxide) undecyl alpha-methacrylate (PVCL-g-C11EO42) have been characterized using turbidimetry and small-angle neutron scattering (SANS). Turbidity measurements show that the addition of SDS to a dilute aqueous copolymer solution (1.0 wt %) induces an increase of the cloud point (CP) value and a decrease of the turbidity at high temperatures. In parallel, SANS results show a decrease of both the average distance between chains and the global size of the objects in solution at high temperatures as the SDS concentration is increased. Combination of these findings reveals that the presence of SDS in the PVCL-g-C11EO42 solutions (1.0 wt %) promotes the formation of smaller aggregates and, consequently, leads to a more homogeneous distribution of the chains in solution upon heating of the mixtures. Moreover, the SANS data results show that the internal structure of the formed aggregates becomes more swollen as the SDS concentration increases. On the other hand, the addition of moderate amounts of SDS (up to 4 mm) to a semidilute copolymer solution (5.0 wt %) gives rise to a more pronounced aggregation as the temperature rises; turbidity and SANS studies reveal in this case a decrease of the CP value and an increase of the scattered intensity at low q. The overall picture that emerges from this study is that the degree of aggregation can be accurately tuned by varying parameters such as the temperature, level of surfactant addition, and polymer concentration.     

Solvent effect on the aggregation behavior of rod-coil diblock copolymers

The water-induced aggregation behavior of rod-coil diblock copolymers based on poly(ethylene oxide) (PEO) and poly{(+)-2,5-bis[4'-((S)-2-methylbutoxy)phenyl]styrene} (PMBPS), PEO104-b-PMBPS53, was investigated in the common solvent THF and in the selective solvent dioxane. Before adding water, PEO104-b-PMBPS53 stayed as single polymer chains no matter what conformation the PEO block took (i.e., either the random coil conformation in THF or the compact globule conformation in dioxane). The critical water content ( approximately 6 wt %) at which PEO104-b-PMBPS53 began to aggregate was also similar in both solvents, indicating that PMBPS dominated the aggregation process. However, the size, the size distribution, and the morphology of aggregates in THF/water were quite different from those in dioxane/water. Narrowly distributed spheres with Rh approximately 20 nm were observed in dioxane, whereas in THF, a bimodal distribution peaked at 3 and approximately 300 nm, was observed. The results from 2D wide-angle X-ray diffraction and polarized optical microscopy demonstrated that the PMBPS blocks packed in a parallel pattern upon aggregation in dioxane/water. The anisotropic disclike structures observed in THF/water also indicated the orientation of the PMBPS blocks upon forming aggregates in dilute solution.     

Effects of polymer aggregation and quencher size on amplified fluorescence quenching of conjugated polyelectrolytes

The fluorescence of conjugated polyelectrolytes (CPEs) is efficiently quenched by low concentrations of quenchers with opposite charges. We have reported the close correlation between this amplified quenching phenomenon and CPE chain aggregation. In this paper, we further demonstrate the profound correlation between the fluorescence quenching efficiency, CPE chain aggregation, and quencher molecular size. Aggregation of a poly(phenylene ethynylene)-type CPE (PPE-CO2-) is induced by the addition of either water or Ca2+ to methanol solution, as indicated by absorption, fluorescence, dynamic light scattering, and fluorescence microscope measurements. For quencher ions with a small molecular size, such as methyl viologen (MV2+), either the loose (induced by the addition of Ca2+) or the compact (induced by the addition of water) CPE chain aggregates are beneficial to the fluorescence quenching. For quencher ions with large molecular size, such as tris(4,7-diphenyl-1,10-phenanthroline)ruthenium (Ru(dpp)32+), however, the loose chain aggregates are found to be favorable for quenching, while the quenching efficiency is lower for the compact polymer aggregates present in aqueous solution.     

Nanoparticle-assembled capsule synthesis: formation of colloidal polyamine-salt intermediates

There is current interest in developing new synthesis strategies for multifunctional hollow spheres with tunable structural properties that would be useful in encapsulation and controlled release applications. A new route was reported recently, in which the sequential reaction of polyamines, multivalent anions, and charged nanoparticles leads to the formation of polymer-filled and water-filled organic/inorganic micron-sized structures known as nanoparticle-assembled capsules. This technique is unique among other capsule preparation routes, as it allows the rapid and scalable formation of robust shells at room temperature, in near-neutral water, and with readily available precursors. This nanoparticle assembly synthesis route involves two steps: the formation of polymer aggregates and the subsequent deposition of particles around the aggregates. The purpose of this paper is to understand in greater detail the noncovalent chemistry of the polymer-salt aggregation step. With poly(allylamine hydrochloride) (PAH) as the model polymer, aggregate formation was investigated as a function of charge ratio, pH, and time through dynamic light scattering, electrophoretic mobility measurements, chloride ion measurements, and optical microscopy. PAH formed aggregates by the cross-linking action of divalent and higher-valent anions above a critical charge ratio and in a pH range defined by the pKa values of PAH and the anion. The aggregates grew in size through coalescence and with growth rates that depended on their surface charge. Controlling polymer aggregate growth provided a direct and simple means to adjust the size of the resultant capsule materials.     

Poly(styrene-b-2-vinylpyridine-1-oxide) diblock copolymers: 3. Microemulsions in water/propan-2-ol/toluene mixtures

Pseudo-ternary phase diagrams have been constructed for the three-component solvent system (toluene+water+propan-2-ol) containing diblock copolymers of poly(styrene-b-2-vinylpyridine-1-oxide). Microemulsions have been shown to form on the water-rich side of the phase diagram, in the region of the phase boundary without polymer. Dynamic light-scattering experiments have led to droplet size values in the region of 100 nm, with the size depending strongly on the propan-2-ol/water concentration, as well as the amount of solubilised toluene in the core. Viscometry experiments have been carried out to measure polymer aggregation numbers in the microemulsion droplets, and interfacial tension measurements have shown that in the absence of propan-2-ol (effectively a cosurfactant) the limiting value of the oil/water interfacial tension, even an saturation adsorption of the copolymer is 20 mNm^–1. However, addition of propan-2-ol reduces the interfacial tension to the very low values generall commensurate with microemulsion formation.     

Ordered Solid‐State Microstructures of Conjugated Polymers Arising from Solution‐State Aggregation

Controlling the solution‐state aggregation of conjugated polymers for producing specific microstructures remains challenging. Herein, a practical approach is developed to finely tune the solid‐state microstructures through temperature‐controlled solution‐state aggregation and polymer crystallization. High temperature generates significant conformation fluctuation of conjugated backbones in solution, which facilitates the polymer crystallization from solvated aggregates to orderly packed structures. The polymer films deposited at high temperatures exhibit less structural disorders and higher electron mobilities (up to two orders of magnitude) in field‐effect transistors, compared to those deposited at low temperatures. This work provides an effective strategy to tune the solution‐state aggregation to reveal the relationship between solution‐state aggregation and solid‐state microstructures of conjugated polymers.     

Modulation of emulsion rheology through electrostatic heteroaggregation of oppositely charged lipid droplets: influence of particle size and emulsifier content

The influence of electrostatically-induced heteroaggregation of oppositely charged lipid droplets on the rheology and stability of emulsions has been studied. 20 wt.% oil-in-water emulsions (pH 6) containing oppositely charged droplets were fabricated by mixing cationic lactoferrin-coated lipid droplets with anionic β-lactoglobulin-coated lipid droplets. Emulsions containing mixtures of droplets with different charges (positive or negative) and sizes (large or small) were prepared, and then their overall particle characteristics (ζ-potential and size) and rheology were measured. Emulsions formed by mixing positive droplets and negative droplets that were both relatively small (d(43) ≈ 0.3 μm) exhibited extensive flocculation and had paste-like properties at intermediate positive-to-negative particle ratios. On the other hand, emulsions formed by mixing positive droplets and negative droplets that were both relatively large (d(43) ≈ 3 μm) exhibited little aggregation and had relatively low viscosities at all particle ratios. Emulsions with small negative droplets and large positive droplets (or vice versa), exhibited some aggregation and viscosity enhancement at intermediate particle ratios. The presence of relatively high levels of protein in the aqueous phase of mixed emulsions reduced the level of droplet aggregation and viscosity enhancement observed, which was attributed to the ability of protein molecules to bind to droplet surfaces and neutralize their charges. Electrostatically-induced heteroaggregation of lipid droplets may be a useful means of controlling the physicochemical properties of emulsion-based products in the food, personal care, pharmaceutical and cosmetic industries.     

Protein partitioning in thermoseparating systems of a charged hydrophobically modified ethylene oxide polymer

The phase behavior of a thermoseparating cationic hydrophobically modified ethylene oxide polymer (HM-EO) containing tertiary amines has been investigated at different pH, salt and sodium dodecyl sulfate (SDS) concentrations, in order to find a water/HM-EO two-phase system suitable for protein partitioning. The used polymer forms micellar aggregates that can be charged. By changing pH and SDS concentrations the netcharge of the SDS/HM-EO aggregate can be shifted from positive to negative. Bovine serum albumin (BSA) and lysozyme were partitioned in the thermoseparated two-phase systems of the cationic polymer at different pH, salt and SDS concentrations. The dominant attractive interactions between the polymer aggregates and the studied proteins were shown to be of electrostatic (Coulomb) nature rather than hydrophobic interaction. At low ionic strength the positively charged polymeric aggregates attracted negatively charged BSA and repelled positively charged lysozyme. Upon addition of SDS the negatively charged aggregates attracted lysozyme and repelled BSA. Thus, it was possible to direct proteins with different charges to the polymeric phase and redirect them to a polymer-depleted phase by changing the netcharge of the polymeric aggregates. The effect of different salts on the partitioning of BSA in a system of slightly positively charged HM-EO was studied. NaCl and KBr have a significant effect on driving the BSA to the polymer-depleted phase, whereas KF and K2SO4 have a smaller effect on the partitioning. The cloud point temperature of the charged polymer decreased upon addition of SDS near the isoelectric molar ratio of SDS to polymer and also upon salt addition. In the latter case the decrease was smaller than expected from model calculations based on Flory-Huggins theory, which were performed for a charged thermoseparating polymer at different charges and salt concentrations.     

PEO-PS共聚微粒在MgSO4溶液中聚集的分形

可溶性高聚物的聚集动力学研究在物理、化学、生物和医学工程等诸多领域都极有理论和实际应用价值，这方面的工作国外多有报导［‘，’，“］．最近Napper与他的合作者Zhu又报导用聚地异丙基丙烯酸胺（PNIPAM）空间稳定的聚苯乙烯（PS）微乳粒子在NaNO。中的聚集动力学研究［‘’］．指出该粒子的聚集生长遵循指数规律，聚集速率和描述生长过程的分形值（fractal山mension）随着NaNO。的浓度和温度增加·在所研究的条件范围内粒子的聚集过程属扩散限制型簇聚集（dffesion－h。tedclusteraggregation，DLCA．本文将报导用不同摩to＄…     

Poly(ethyleneimine) as reducing and stabilizing agent for the formation of gold nanoparticles in w/o microemulsions

This paper is focused on the use of branched poly(ethyleneimine) (PEI) as reducing as well as stabilizing agent for the formation of gold nanoparticles in different media. The process of nanoparticle formation was investigated, in the absence of any other reducing agents, in microemulsion template phase in comparison to the nucleation process in aqueous polymer solution.

On the one hand, it was shown that the polyelectrolyte can be used for the controlled single-step synthesis and stabilization of gold nanoparticles via a nucleation reaction and particles with an average diameter of 7.1 nm can be produced.

On the other hand, it was demonstrated that the polymer can also act as reducing and stabilizing agent in much more complex systems, i.e. in water-in-oil (w/o) microemulsion droplets. The reverse microemulsion droplets of the quaternary system sodium dodecylsulfate (SDS)/toluene–pentanol (1:1)/water were successfully used for the synthesis of gold nanoparticles. The polymer, incorporated in the droplets, exhibits reducing properties, adsorbs on the surface of the nanoparticles and prevents their aggregation. Consequently, nanoparticles of 8.6 nm can be redispersed after solvent evaporation without a change of their size.

Nevertheless, the polymer acts already as a “template” during the formation of the nanoparticles in water and in microemulsion, so that an additional template effect of the microemulsion is not observed.

The particle formation for both methods is checked by means of UV–vis spectroscopy and the particle size and size distribution are investigated via dynamic light scattering and transmission electron microscopy (TEM).