Controlled release of acetochlor from poly (butyl methacrylate-diacetone acrylamide) based formulation prepared by nanoemulsion polymerisation method and evaluation of the efficacy

Acetochlor is an important herbicide for gramineous weeds and some small seed broadleaf weeds. Controlled-release formulations of herbicide are highly desirable not only for attaining the most effective utilisation of the weed control, but also for reducing environmental pollution. Acetochlor was incorporated in poly (butyl methacrylate-diacetone acrylamide) based formulation to obtain controlled release properties. The acetochlor nanocapsules were characterised by size distribution, infrared spectroscopy (IR) and field emission scanning electron microscopy (FESEM), and factors related to loading efficiency, swelling behaviour of the formulation were investigated. For this controlled-release formulation, the loading efficiency could reach about 50% (w/w). n, the diffusion parameter was indicative of the transport mechanism, and the values for ‘n’ were in the range of 0.28–0.61, which indicated that the release of acetochlor was diffusion-controlled. The time taken for 50% of the active ingredient to be released into water, t₅₀, was also calculated for the comparison of formulations in different conditions. The formulation with higher temperature and more diacetone acrylamide had lower value of t₅₀, which means a quicker release of the active ingredient. This study highlighted some pieces of evidence that improved herbicide incorporation and slower release were linked to potential interactions between the herbicide and the polymer.     

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     

Rotaxane‐Like Structures Threaded through the Pores of Hollow Porous Nanocapusles

Nanocapsules with molecules threaded through the porous shells may lead to advanced cell‐mimicking functional devices. Herein, we show the feasibility of synthesizing such hybrid nanostructures by using vesicle‐templated polymer nanocapsules with controlled nanopores. Ship‐in‐a‐bottle assembly inside a nanocapsule created an internal unit. An external unit was then connected to an entrapped internal unit through pre‐attached linker threaded through a nanopore in the shell of the nanocapsule. Both internal and external units are larger than the pore size and cannot cross the shell, producing a rotaxane‐like structure. Successful synthesis was achieved with fairly short linkers (six and ten carbon atoms in a chain), creating an opportunity for facile synthesis of functional devices capable of cross‐shell communication.     

One step nanoencapsulation of corrosion inhibitors for gradual release application

The direct application of corrosion inhibitors on metal surfaces is potentially dangerous for the environment and the restoration operators, thus new conservation strategies are mandatory. In this study, two copper corrosion inhibitors, 1H-benzotriazole (BTA) and 5-phenyl-1H-tetrazole (PT), are encapsulated in a silica nanocontainer, for future application in smart coatings, with the aim to reduce the amount of chemicals used in treatments, their dispersion in the environment and the direct exposure of the operators to these chemicals. In particular, composite silica nanocapsules, containing the corrosion inhibitors, are prepared via one-step synthesis, based on mini-emulsion polymerisation processes.The morphology, structure, and texture of these loaded silica nanocontainers are characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ physisorption (BET/BJH). Micro-Raman spectroscopy (RS) is performed to characterise the composition. UV–visible spectroscopy and thermal analysis (TG/DSC) are performed for the loading and encapsulation efficiency (L%, EE%) study.Synthesised nanocapsules show a core-shell structure and, when loaded with the inhibitors, have size ranging from about 130 to 170 nm and a BET surface area of the order of 800 m²/g. The EE% is maximum in the case of BTA and decreases to ～52% in the case of PT.     

Smart Coatings Prepared via MAPLE Deposition of Polymer Nanocapsules for Light-Induced Release

Herein, smart coatings based on photo-responsive polymer nanocapsules (NC) and deposited by laser evaporation are presented. These systems combine remotely controllable release and high encapsulation efficiency of nanoparticles with the easy handling and safety of macroscopic substrates. In particular, azobenzene-based NC loaded with active molecules (thyme oil and coumarin 6) were deposited through Matrix-Assisted Pulsed Laser Evaporation (MAPLE) on flat inorganic (KBr) and organic (polyethylene, PE) and 3D (acrylate-based micro-needle array) substrates. SEM analyses highlighted the versatility and performance of MAPLE in the fabrication of the designed smart coatings. DLS analyses, performed on both MAPLE- and drop casting-deposited NC, demonstrated the remarkable adhesion achieved with MAPLE. Finally, thyme oil and coumarin 6 release experiments further demonstrated that MAPLE is a promising technique for the realization of photo-responsive coatings on various substrates.     

萘基相互连接的多孔碳纳米囊的制备及超电容性能

以萘为碳源, 采用MgO模板诱导耦合KOH裁剪技术制备了相互连接的多孔碳纳米囊(ICNC). 结果表明所制备的ICNC₂具有大的比表面积(1811 m²/g)、 高的压实密度(1.38 g/cm³)和微孔孔容含量(58.93%). 在对称的超级电容器(SC)中, ICNC₂电极的体积比容在不同电流密度下分别高达420.8 F/cm³(0.069 A/cm³)和315 F/cm³(27.6 A/cm³), 容量保持率为74.82%. 在38 W/L功率密度下, ICNC₂基SC的体积能量密度为14.6 W?h/L. 经过20000次循环后, 其体积比容仅衰减1.4%, 库伦效率为99.1%, 为从萘基小分子制备储能用功能碳材料提供了一种可行的方法.     

Simple but Precise Engineering of Functional Nanocapsules through Nanoprecipitation

A general, rapid, and undemanding method to generate at will functional oil‐filled nanocapsules through nanoprecipitation is reported. On the basis of polymer and hexadecane/water/acetone phase diagrams, the composition can be set so that polymer chains preferentially stick at the interface of the oil droplets to create nanocapsules. The nanocapsules can be decorated with biorelevant molecules (biotin, fluorescent tags, metal nanoparticles) within the shell and loaded with hydrophobic molecules in a simple one‐pot procedure.     

Highly Stable,Water‐Dispersible Metal‐Nanoparticle‐Decorated Polymer Nanocapsules and Their Catalytic Applications

A facile synthesis of highly stable, water‐dispersible metal‐nanoparticle‐decorated polymer nanocapsules (M@CB‐PNs: M=Pd, Au, and Pt) was achieved by a simple two‐step process employing a polymer nanocapsule (CB‐PN) made of cucurbit[6]uril (CB[6]) and metal salts. The CB‐PN serves as a versatile platform where various metal nanoparticles with a controlled size can be introduced on the surface and stabilized to prepare new water‐dispersible nanostructures useful for many applications. The Pd nanoparticles on CB‐PN exhibit high stability and dispersibility in water as well as excellent catalytic activity and recyclability in carbon–carbon and carbon–nitrogen bond‐forming reactions in aqueous medium suggesting potential applications as a green catalyst.