Antiseptic Nanocapsule Formation via Controlling Polymer Deposition onto Water-in-Oil Miniemulsion Droplets

The stable nanodroplet was prepared by inverse miniemulsion with an aqueous antiseptic solution dispersed in an organic medium of solvent/nonsolvent mixture containing an oil-soluble surfactant and the polymer for shell formation. The change in gradient of the solvent/nonsolvent mixture, obtained by heating at 50 °C, led to the precipitation of the polymer in the organic phase and deposition onto the large interphase of the aqueous miniemulsion droplets. The monodisperse polymer nanocapsule, with the size range of 80–240 nm, dispersed in cyclohexane phase was achieved as a function of surfactant concentration. By variation of polymer content, molecular weight and type, an encapsulation efficiency of 20–100% was obtained as detected by proton-nuclear magnetic resonance spectroscopy measurement. The nanocapsule could be easily transferred into water as continuous phase resulting in aqueous dispersion with nanocapsule containing the antiseptic agent as an aqueous core. The encapsulated amount of the antiseptic agent was evaluated to indicate the durability of the nanocapsule's wall. Additionally, the different types of polymer having glass transition temperature ranging from −60 to 100°C have been successfully used. Currently, the research work on the incorporation of nanocapsules onto natural rubber (NR) latex in order to prepare NR latex glove containing the antiseptic agent nanocapsules is carried out. By using the simple and versatile layer-by-layer (LbL) technique based mainly on an electrostatic interaction between oppositely charged species, the deposition of nanocapsules onto NR latex film has successfully been fulfilled.     

Thermally reversible pluronic/heparin nanocapsules exhibiting 1000-fold volume transition

Novel Pluronic/heparin composite nanocapsules that exhibit a thermally responsible swelling and deswelling behavior were synthesized. Pluronic F-127 preactivated with p-nitrophenyl chloroformate at its two terminal hydroxyl groups was dissolved in a methylene chloride phase. The organic phase was dispersed in an aqueous phase containing heparin. At an organic/aqueous interface, Pluronic-cross-linked heparin nanocapsules were produced. They exhibited a 1000-fold volume transition (ca. 336 nm at 25 degrees C; ca. 32 nm at 37 degrees C), and a reversible swelling and deswelling behavior when the temperature was cycled between 20 and 37 degrees C. The reversible volume transition of Pluronic nanocapsules was caused by micellization and demicellization of cross-linked Pluronic polymer chains within the nanocapsule structure in response to temperature. The morphological characters were investigated with transmission electron microscopy and small angle neutron scattering. Pluronic/heparin nanocapsules had an aqueous fluid-filled hollow interior with a surrounding shell layer below the critical temperature, but they became a collapsed core/shell structure similar to that of Pluronic micelles above it.     

On the Stability of Liquid Nanodroplets in Polymerizable Miniemulsions

Liquid nanodroplets within a size range of 50 to 500 nm can easily be prepared by shearing a system containing oil, water and a surfactant. The growth of the nanodroplets can effectively be suppressed by using a strong hydrophobe as an additivie to the oil and an effective surfactant. The hydrophobe acts as an osmotic agent which stabilizes the system against Ostwald ripening. The growth of the droplets by collision is controlled by the density of the surfactant layer. Freshly prepared miniemulsions are “critically stabilized” and show a slow, but pronounced growth, whereas a miniemulsion in “equilibrium” exhibits constant droplet size on longer time scales. Polymerization of the oil droplets of such miniemulsions turns out to be very promising and extends the possibilities of classical emulsion polymerization. Since each droplet can be considered a small reactor in which polymerization reactions take place, the process allows one to create new particle structures, e.g. polyaddition reactions can take advantage of unusual monomers, the incorporation of materials which are not soluble in the continuous phase, and the formation of nanocapsules.     

An improved interfacial coacervation technique to fabricate biodegradable nanocapsules of an aqueous peptide solution from polylactide and its block copolymers with poly(ethylene glycol)

ABA block copolymers of polylactide and poly(ethylene glycol) as amphiphilic bioabsorbable polymers were synthesized by the ring-opening polymerization of dl- lactide onto poly(ethylene glycol) (PEG 2000 or PEG 6000) and their structures were characterized on the basis of proton NMR. Biodegradable nanocapsules of an aqueous insulin solution were prepared from the block copolymers and polylactide by an improved interfacial coacervation technique. The results showed that the diameters of the nanocapsules were mainly dependent on the ratio of the two chains in the block polymers. The size of the nanocapsules decreased with an increase in the amount of surfactant used. More insulin solution resulted in an enlargement of the nanocapsules in diameter. In an optimum condition, biodegradable nanocapsules could be achieved with a size around 250 nm with a narrow distribution. The encapsulation percentages of insulin were larger in the nanocapsules from the PEG 2000 copolymers than in those from the PEG 6000 analogs and changed with the ratios of the blocks in the block copolymers. Received: 17 July 2000 Accepted: 24 November 2000     

Viscosity behavior of silica suspensions flocculated by associating polymers

Associating polymers are hydrophilic long-chain molecules containing a small number of hydrophobic groups, and act as flocculants in aqueous suspensions. The effects of associating and nonassociating polymers on viscosity behavior are studied for silica suspensions. Since flocculation is induced by polymer bridging, the viscosity behavior is converted from Newtonian to shear-thinning profiles. The additions of surfactant cause an increase in viscosity for suspensions prepared with associating polymer, whereas the flow behavior of suspensions with nonassociating polymer is not significantly influenced. In adsorption of associating polymers onto silica particles, the chain may adopt a conformation with a water-soluble backbone attached to the particle surfaces. The hydrophobic groups extending from the chains adsorbed onto different particles can form a micelle by association with surfactant. Therefore, the bridging flocculation is enhanced by surfactant. The cooperative micellar formation between associating polymer and surfactant is responsible for viscosity increase in suspensions.     

N-异丙基丙烯酰胺对细乳液聚合制备纳米胶囊形态的影响

将N-异丙基丙烯酰胺(NIPAAm)引入小分子烃为模板的苯乙烯细乳液聚合法制备纳米胶囊的体系.水相引发形成的聚异丙基丙烯酰胺(PNIPAAm)低聚物自由基在聚合温度下(大于其最低临界溶解温度)析出并被苯乙烯细乳液液滴吸附,在热力学推动力和静电斥力的共同作用下,PNIPAAm低聚物倾向于分布在液滴和水的界面上,使液滴界面成为主要的聚合场所,单体从液滴内部向界面扩散补充消耗的单体,生成的聚合物在液滴界面上析出,包覆小分子烃液滴,最终得到纳米胶囊.通过透射电镜观察粒子形态和大小;利用接触角测定仪测定了细乳液液滴的表面张力.考察了NIPAAm用量、油溶性单体/小分子烃比例、交联剂用量及乳化剂和引发剂对的种类对胶囊形态的影响.     

DNA amplification via polymerase chain reaction inside miniemulsion droplets with subsequent poly(n-butylcyanoacrylate) shell formation and delivery of polymeric capsules into mammalian cells

There is a growing interest in the development of stable nanocapsules that could deliver the bioactive compounds within the living organism, and to release them without causing any toxic effects. Here the miniemulsion droplets were first used as "nanoreactors" for the amplification of single-molecule dsDNA template (476 and 790 base pairs) through PCR. Afterwards, each droplet was surrounded with a biodegradable PBCA shell by interfacial anionic polymerization, enabling therefore to deliver the PCR products into the cells. The size of the initial miniemulsion droplets and the final polymeric capsules was in the range of 250 and 320 nm, mainly depending on the type of the continuous phase and presence of dsDNA template molecules. The formation of PCR products was resolved with gel electrophoresis and detected with fluorescence spectroscopy in the presence of DNA specific dye (SYBRGreen). TEM studies were performed to prove the formation of the polymeric shell. The shell thickness was measured to be within 5-15 nm and the average molecular weight of the formed PBCA polymer was around 75000 g · mol(-1) . For the cell uptake experiments, the obtained nanocapsules were transferred from the organic phase into aqueous medium containing a water-soluble surfactant. The effect of the surfactant type (anionic, cationic or non-ionic) on the HeLa cell viability and nanocapsule uptake behavior was studied by CLSM and FACS. Confocal analysis demonstrated that nanocapsules stabilized with cationic (CTMA-Cl) and non-ionic (Lutensol AT50) surfactants show almost the same uptake, whereas capsules redispersed in anionic (SDS) surfactant possess a 30% higher uptake. The release of the encapsulated material within the cell was studied on the example of Cy5-labeled oligonucleotides showing the colocalization with mitochondria of MSCs cells.     

Thermal and acid labile polyurethanes as a new class of responsive materials in polymeric nanoparticles and nanocapsules

A new class of polyurethanes has been designed, containing tertiary carbamate groups in the main chain of the polymer, which enable the resulting polymer to degrade completely under acid and thermal treatment. The decomposition temperatures of the polymers were determined by measuring the evolution of carbon dioxide and other decomposition products using TGA‐MS. Until decomposition of the polymer, no glass transition was found. The polymers exhibit excellent solubility in common organic solvents like chloroform and tetrahydrofuran, making them to suitable materials for film formation. From the obtained polymers, nanoparticles were synthesized by the solvent evaporation method combined with the miniemulsion technique. The resulting nanoparticles can be used as intelligent fillers in films and sensors, since they degrade at temperatures of above 180 °C, which can be detected by a color change reaction with ninhydrin. Polymeric nanocapsules were prepared by an interfacial polyaddition reaction from 2,4‐toluene diisocyanate and tertiary diols performed at the droplet's interface in inverse (water‐in‐oil) miniemulsions. These nanocapsules with an encapsulated photoacid generator can act as a release system, whereby an acidic release through irradiation with ultraviolet light can be triggered. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Nanoinclusions in cryogenically quenched nanoemulsions

Nanodroplets containing mixtures of silicone oil and squalene are dispersed in a simple aqueous surfactant solution, quenched in liquid ethane, and examined using cryogenic transmission electron microscopy (CTEM). Depending on the phase of ice that forms around the nanodroplets and on the composition of the oil mixture, nanoinclusions can be observed inside oil nanodroplets, independent of surfactant type. Our observations suggest that these nanoinclusions arise from nucleation of vapor cavities as the water freezes and expands while the oil remains liquid during the quench.     

Synthesis of polymer particles and nanocapsules stabilized with PEO/PPO containing polymerizable surfactants in miniemulsion

We describe the miniemulsion polymerization of vinyl monomers stabilized in the presence of the polymerizable anionic surfactant Tego XP-1008 and the polymerizable nonionic surfactant Tego XP-1007. Different amounts of polymerizable surfactants and various types of initiators were used to investigate the size and the stability of the final latex particles by transmission electron microscopy and dynamic light-scattering measurements. The grafting of the polymerizable surfactants onto the surface of the latex particles was checked by NMR and XPS measurements and was found to be efficient. Finally, polymerizations of appropriate formulations containing divinylbenzene with the polymerizable surfactant Tego XP-1008 in the presence of a larger amount of hydrophobic agent produced nanocapsules.     

A novel family of ordered,mesoporous inorganic/organic hybrid polymers containing covalently and multiply bound microporous organic hosts

We have prepared a new family of periodic hybrid polymers containing microporous cavities provided by covalently bound organic hosts. Cyclodextrin (CD) or calixarene (CX) hosts are attached to four or more trialkoxysilyl groups, which are polymerized to form a polysilsesquioxane matrix. Structural integrity is provided by copolymerization with tetraethoxysilane, which produces a polysilicate co-matrix. Periodic order is created by carrying out the polymerization in the presence of a surfactant, cetyltrimethylammonium bromide. The resulting as-synthesized polymers from these three starting materials were characterized by solid-state nuclear magnetic resonance spectroscopy. The (13)C and (29)Si spectra provided evidence for intact polysilsesquioxane, polysilicate, organic host, and surfactant. Removal of the surfactant by washing produced a polymer containing cavities of mesoporous dimensions, in addition to the microporous host cavities. The purpose of introducing mesoporosity is to allow enhanced access of guests to the microporous hosts. Transmission electron microscopy demonstrated that both as-synthesized and solvent-extracted polymers have a periodic structure. All polymers are completely insoluble in water. The as-synthesized CD-containing polymers extracted up to >99% of 4-nitrophenol from aqueous solution, and the solvent-extracted CX-containing polymers extracted up to 67% of Fe(3+) and lesser amounts of other metal cations from aqueous solution, with interesting selectivity patterns. Simple filtration then removes the polymer containing the extracted organic molecule or metal cation. These extraction abilities are superior to previous materials.     

Binding of dodecyltrimethylammonium bromide to pH-responsive nanocolloids containing cross-linked methacrylic acid-ethyl acrylate copolymers

The binding of dodecyltrimethylammonium bromide (DoTab) to cross-linked methacrylic acid-ethyl acrylate (MAA-EA) copolymers with various MAA/EA molar ratios at different degrees of neutralization (alpha) was quantitatively studied using isothermal titration calorimetry, dynamic light scattering, surfactant selective electrode, and electrophoresis techniques. The surfactant binds to the polymers at all degrees of neutralization, but via different mechanisms. When alpha is sufficiently high, the binding is primarily electrostatic interaction between the surfactant and ionized polymer chains, which is reinforced by the micellization of electrostatically bound surfactant molecules. The saturation takes place at charge ratio ([DoTa(+)]/[ approximately COO(-)]) close to 1, indicating that the binding is a one-to-one charge neutralization between the cationic surfactant headgroups and anionic carboxylate sites of the polymers. When alpha is low, the binding of DoTab to the unneutralized polymers is driven by the hydrophobic interaction. The onset of hydrophobic binding takes place at DoTab concentration as low as 0.01 mM in 0.05 wt % polymer solution, where the saturation occurs at C(DoTab) approximately 0.19 mM and the amount of bound surfactant is approximately 0.09 mmol of DoTab/(g of polymer) at saturation concentration. The binding results in the formation of the polymer-surfactant complex. For the polymer with low MAA/EA molar ratio, the complex coagulates at a higher DoTab concentration that leads to phase separation; however, for polymers with high MAA/EA molar ratio, the complex remains dispersed and the mixture is stable even at high DoTab concentration.     

超高交联树脂对壬基酚聚氧乙烯醚的吸附机理(英文)

研究了壬基酚聚氧乙烯醚(NPEO-10)在3种具有不同比表面积和孔径大小的超高交联树脂上的吸附行为与机理.3种超高交联树脂对壬基酚聚氧乙烯醚的吸附量受它们的比表面积和孔径大小以及溶液温度的影响.壬基酚聚氧乙烯醚在3种超高交联树脂上的吸附等温线可以用Langmuir和双Langmuir模型很好地拟合,而用Freundlich模型拟合则效果不好,但这些拟合曲线都具有相似的形状.热力学分析表明吸附过程主要表现为吸附质分子的疏水部分和吸附剂表面的作用以及吸附质分子在其表面形成胶束状的聚集体,即分散的、单层及双层聚集体的混合分布.吸附动力学曲线中的两个平台也证明了吸附过程存在单层和双层聚集体.脱附研究为实现超高交联树脂吸附分离水溶液中的壬基酚聚氧乙烯醚提供了合适的操作条件.     

Polymer-surfactant Interactions

Aqueous solutions containing poly(vinyl-pyrrolidone) and sodium caprylate, or poly(vinyl-pyrrolidone) and tetraethylammonium perfluorooctanesulfonate,respectively, have been investigated by volumetric, ionic conductivity and surface tension methods. The presence of an interaction region has been determined from conductivity and surface tension. The width of such a region depends on the amount of polymer in the mixture,temperature, surfactant content and added electrolyte (NaCl). The observed behaviour was explained in terms of the combined effects played by the alkyl-chain hydophobicity, polar head group(s) and counter-ions. An approximate solution to a mass action model for the binding of surfactants onto polymers has been introduced. It allows determining the width of the interaction region as a function of polymer mass percent in the mixture. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of oily core‐hybrid shell nanocapsules through interfacial free radical copolymerization in miniemulsion: Droplet formation and nucleation

Nanocapsules with an oily core and an organic/inorganic hybrid shell were elaborated by miniemulsion (co)polymerization of styrene, divinylbenzene, γ‐methacryloyloxy propyl trimethoxysilane, and N‐isopropyl acrylamide. The hybrid copolymer shell membrane was formed by polymerization‐induced phase separation at the interface of the oily nanodroplets with water. It was shown that the size, size distribution, and colloidal stability of the miniemulsion droplets were extremely dependent on the nature of the oil phase, the monomer content and the surfactant concentration. The less water‐soluble the hydrocarbon template and the higher the monomer content, the better the droplet stability. The successful formation of nanocapsules with the targeted core‐shell morphology (i.e., a liquid core surrounded by a solid shell) was evidenced by cryogenic transmission electron microscopy. Both nanocapsules and nanoparticles were produced by polymerization of the miniemulsion droplets. The proportion of nanoparticles increased with increasing monomer concentration in the oil phase. These undesirable nanoparticles were presumably formed by homogeneous nucleation as we showed that micellar nucleation could be neglected under our experimental conditions even for high surfactant concentrations. The introduction of γ‐methacryloyloxy propyl trimethoxysilane was considered to be the main reason for homogeneous nucleation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 593–603, 2010     

Immobilization of α-chymotrypsin into the poly(N,N-diallyl-N,N-didodecyl ammonium bromiae)/surfactant nanocapsules

The biocatalytic systems from nanocapsules containing α-chymotrypsin in the inner aqueous cavities have been prepared. They can act in both the organic solvent and the aqueous medium. For such encapsulation, the reversed hydrated micelles from N,N-diallyl-N,N-didodecyl ammonium bromide (DDAB) in cyclohexane (w₀ = 22), including α-chymotrypsin, have been polymerized by UV initiation. After precipitation by acetone, these nanocapsules were moved into the aqueous medium with the aid of ionic, AOT, or nonionic, Brij-97, surfactants. In this case, the unilamellar liposomes were formed. They have the inner monolayer from the poly-DDAB network, and the outer one predominantly from surfactant molecules. According to the light-scattering data, the average outer diameter of nanocapsules equals to 20 nm. The vesicular “coated” α-chymotrypsin was used for study of enzymatic activity. It has been shown using the integral form of the Michaelis-Menten equation, that by encapsulation of α-chymotrypsin the value of the Michaelis constant, K_m, increases by a factor of 1.8 by the ATEE hydrolysis. However, the value of the maximal velocity, V_max, decreases by a factor of 1.7. Encapsulated α-chymotrypsin has a high thermostability keeping its own activity up to 80°C. The polymer network blocks the conformational transitions of enzyme molecule by heating of a system.     

Experimental evidence for internal structure in aqueous-organic nanodroplets

The spatial distribution of species within an aerosol droplet influences how it interacts with its environment. Despite the ubiquity of multicomponent nanodroplets in natural and technological aerosols, there are no published measurements of their internal structure. Here, we report the first experimental results for structure in aqueous organic nanodroplets based on small angle neutron scattering by high number density aerosols. For H(2)O-n-butanol droplets, fitting of the diffraction patterns confirms the picture of an aqueous core containing approximately 3 mol% alcohol covered by a shell of densely packed alcohol molecules.     

Fabrication of mesoporous silica/polymer composites through solvent evaporation process and investigation of their excellent low thermal expansion property

We fabricate mesoporous silica/epoxy polymer composites through a solvent evaporation process. The easy penetration of the epoxy polymers into mesopores is achieved by using a diluted polymer solution including a volatile organic solvent. After the complete solvent evaporation, around 90% of the mesopores are estimated to be filled with the epoxy polymer chains. Here we carefully investigate the thermal expansion behavior of the obtained mesoporous silica/polymer composites. Thermal mechanical analysis (TMA) charts revealed that coefficient of linear thermal expansion (CTE) gradually decreases, as the amount of the doped mesoporous silica increases. Compared with spherical silica particle without mesopores, mesoporous silica particles show a greater effect on lowering the CTE values. Interestingly, it is found that the CTE values are proportionally decreased with the decrease of the total amount of the polymers outside the mesopores. These data demonstrate that polymers embedded inside the mesopores become thermally stable, and do not greatly contribute to the thermal expansion behavior of the composites.     

Membrane emulsification and solvent pervaporation processes for the continuous synthesis of functional magnetic and Janus nanobeads

We discuss the integration of membrane emulsification and pervaporation processes for the continuous production of functional materials, such as silica-encapsulated magnetite nanoparticle clusters and asymmetric Janus nanoparticles, by the emulsion droplet solvent evaporation method, which has traditionally been performed in small-scale batch systems. An organic solvent containing primary magnetite nanoparticles (～10 nm) coated with oleic acid was dispersed in a continuous aqueous phase by membrane emulsification, which enabled the consistent production of nanoparticle-laden solvent droplets of well-controlled size with narrow size distributions. The solvent was removed from the emulsion by pervaporation. Prior to complete solvent removal, the nanoparticle packing density within the clusters was a function of the residence time in the pervaporation unit. The final clusters formed, ～100-300 nm in size, exhibited the same superparamagnetic behavior as the primary nanoparticles, and were stable in aqueous media with a zeta potential of -70 mV at neutral pH. A facile method was used to coat the nanoclusters with a silica shell, providing sites for surface functionalization with a range of organic ligands. The nanoparticles and clusters were analyzed by a variety of techniques, including TGA, DLS, TEM, EDS, and SQUID. The effects of various parameters, such as the membrane dimensions and flow rate through the unit, on the mass transport rates were elucidated through a parametric modeling study. The applicability of the methods to the production of polymeric beads and more complex particles was demonstrated; to create Janus structures, organic polymer solutions were dispersed as droplets in continuous aqueous phases, and the solvent was subsequently evaporated. The Janus particles consisted either of polymeric cores with magnetite nanoparticles clustered as islands on their surfaces, or of two phase-separated polymers, each constituting half of any given polymeric particle.     

Preparation of raspberry-like nanocapsules by the combination of Pickering emulsification and solvent displacement technique

Well-defined raspberry-like nanocapsules were prepared by the combination of Pickering emulsification and solvent displacement technique by using silica particles as stabilizer and hexadecane (HD) as soft template. The formation of the capsule morphology is caused by the phase separation of poly(styrene-co-4-vinyl pyridine) (poly(St-co-4-VP)) in the droplets due to the diffusion of good solvent for the (co)polymer to the aqueous continuous phase. The size of capsules was successfully reduced from tens of micrometers in the dispersion by simply stirring to the nanorange by the employment of sonication and Ostwald ripening. The formation of silica-particles-armored nanocapsules was confirmed by transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HRSEM), dynamic light scattering (DLS), and zeta potential measurement. The colloidal stability and particle properties, including size and morphology, depend on the amount of HD, and copolymers, the sonication time, the dispersion pH value, the type of solvent, and the copolymer composition.