Fabrication of sustained‐release and antibacterial citronella oil‐loaded composite microcapsules based on Pickering emulsion templates

In this work, the citronella oil (CTO)‐loaded composite microcapsules with hydroxyapatite (HAp)/quaternary ammonium salt of chitosan (HACC)/sodium alginate (SA) shells are facilely and effectively fabricated by templating citronella oil‐in‐water Pickering emulsions, which are stabilized with HAp nanoparticles. The microcapsule composite shells are prepared by the electrostatic adsorption of HACC and SA, and then chelation interaction of alginate and Ca²⁺ ions released from HAp nanoparticles. Scanning electronic microscope observation shows that the microcapsules have a spherical shape. Thereafter, Fourier transform infrared spectroscopy and thermal gravimetric analysis results indicate that CTO is successfully loaded into the microcapsules, and the related CTO‐loaded microcapsules possess the thermal stability. Moreover, the in vitro release study of CTO shows that the microcapsules have sustained release activity, and the related CTO release profiles can be well described by Rigter–Peppas model. The antimicrobial assays of microcapsules display the antibacterial effect of CTO‐loaded microcapsules against Staphylococcus aureus and Escherichia coli. Overall, this study opens up new potentiality for unstable active ingredient as an environmental friendly and ingenious microencapsulation in food and agriculture applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46386.     

Preparation of Tung Oil-Loaded PU/PANI Microcapsules and Synergetic Anti-Corrosion Properties of Self-Healing Epoxy Coatings

Tung oil is used as a catalyst-free repair agent. Tung oil-loaded polyurethane (PU) microcapsules are prepared by interfacial polymerization in a SiO₂-stabilized Pickering emulsion system, polyaniline (PANI) is deposited in situ on the PU microcapsule surface, and tung oil-loaded PU/PANI double-layer shell microcapsules are obtained. Synthesized PU/PANI microcapsules showed the characteristic dark-green color of conductive PANI. The average particle size is 31.1 ± 8.1 µm and the core content is 45.1 ± 4.3 wt%. The microcapsules have a good thermal stability, and the chemical structure of the PU/PANI wall and tung oil core is confirmed by Fourier transform infrared analysis. Self-healing anti-corrosion coatings are prepared by adding 10 wt% microcapsules into epoxy resin. The corrosion resistance properties of the self-healing coating are evaluated by immersing scratched coatings in 10 wt% NaCl solution for 15 days. The self-healing coating with 10 wt% tung oil-loaded PU/PANI microcapsules have the best anti-corrosion property, and slight corrosion do not occur until 15 days after immersion in salt solution. The self-healing and anti-corrosion mechanism are revealed. The tung oil core and the PANI wall of microcapsules contributed synergistically to the excellent self-healing and anti-corrosion properties of the coating through the formation of self-healing films and passivation layers.     

Suspension polymerization based on inverse Pickering emulsion droplets for thermo-sensitive hybrid microcapsules with tunable supracolloidal structures

Polymerization using Pickering emulsion droplets as reaction vessels is being developed to become a powerful tool for fabrication of hybrid polymer particles with supracolloidal structures. In this paper, two kinds of thermo-sensitive hybrid poly(N-isopropylacrylamide) (PNIPAm) microcapsules with supracolloidal structures were successfully prepared from suspension polymerization stabilized by SiO₂ nanoparticles based on inverse Pickering emulsion droplets. SiO₂ nanoparticles could self-assemble at liquid-liquid interfaces to form stable water-in-oil inverse Pickering emulsion. NIPAm monomers dissolving in suspended aqueous droplets were subsequently polymerized at different temperatures. The hollow microcapsules with SiO₂/PNIPAm nanocomposite shells were obtained when the reaction temperature was above the lower critical solution temperature (LCST) of PNIPAm. While the core-shell microcapsules with SiO₂ nanoparticles' shells and PNIPAm gel cores were produced when the polymerization was conducted at the temperature lower than LCST using UV light radiation. The supracolloidal structures with different cores could be tuned by simply changing reaction temperature, which was confirmed by confocal laser scanning microscopy and scanning electron microscopy. The interesting properties of both microcapsules were their ability of reversibly swelling during drying/wetting cycles and responsive to temperature stimulus. Such functional microcapsules may find applications in double control release system due to the presence of the supracolloidal structures and thermo-sensitivity.     

Ultralow Tribological Properties of Polymer Composites Containing [BMIm]PF6‐Loaded Multilayer Wall Microcapsule

Multilayer wall microcapsules efficiently loaded with a lubricant (ionic liquid [BMIm]PF₆) are successfully synthesized via a combination of interfacial and in situ polymerization reactions based on lignin nanoparticle–stabilized Pickering emulsion templates. The resulting microcapsules are spherical in shape, with an ideal structure of a rough outer surface and a smooth inner surface. The mean diameter and wall thickness of the resultant microcapsules are 52 ± 18 µm and 3–6 µm. The core fraction is ≈71.29 wt%. Compared with the pure epoxy resin, the friction coefficient of self‐lubricating composites decreases by 83.6% (from 0.55 to 0.09) and the wear rate decreases by 218 times (from 76.8 × 10^?14 to 0.352 × 10^?14 m³ N^?1 m^?1) by incorporating 20 wt% of the resultant microcapsules into the epoxy resin. It is demonstrated that [BMIm]PF₆, a more efficient lubricant, release from the microcapsules during the friction process produced a boundary lubricating film. The bipolar property of [BMIm]PF₆ makes the lubricating film firmer, which can efficiently prevent direct contact between the resin matrix and counterface. Furthermore, the rough poly(urea‐formaldehyde) outer surface of multilayer microcapsules brings in an improved interface property between the microcapsules and resin matrix.     

Synthesis of ammonium persulfate microcapsule with a polyaniline shell and its controlled burst release

Polymer hydraulic fracturing is important for increasing production during petroleum exploitation. After fracturing, the high-viscosity polymer should be completely decomposed by gel breakers (ammonium persulfate [APS]) to realize high conductivity in the proppant pack. A new series of polyaniline microcapsules loaded with APS for the preparation of delayed-release gel breakers were synthesized via in situ polymerization. The silica nanoparticles were doped in polyaniline to control the release of the encapsulated APS. The morphology, shell wall thickness, and elemental composition of the microcapsules were characterized by scanning electron microscopy, transmission electron microscopy, and two-dimensional scanned energy-dispersive X-ray spectroscopy. The results revealed that the microcapsules were irregularly spherical with average diameters of about 5–6 μm and had shell thicknesses of 150–300 nm, and the silica nanoparticles had been successfully doped in the polyaniline shell. The microcapsules had a burst release pattern, and their initial release time was precisely controlled by adjusting the concentration and temperature of the sodium hydroxide solution. With increased demands for high performance delayed-release microcapsules, the prepared polyaniline microcapsules loaded with APS show great potential for practical applications in petroleum exploitation, self-healing coating, fiber printing, and grease.     

The tough microcapsules of acrylic acid–styrene–isoprene–styrene quadrablock copolymer shell via Pickering emulsion technique

Pickering emulsion technique has been demonstrated a simple method to fabricate the microcapsules. However, the resulted microcapsules are often fragile. This limits their applications. Here, we report that the microcapsules with the nanostructured shell of poly(acrylic acid‐b‐styrene‐b‐isoprene‐b‐styrene) (ASIS), which is of high toughness and elasticity, could be fabricated via Pickering emulsions using ASIS nanoparticles as stabilizing particles. The surfactant‐free ASIS latex (with theoretical molecular weight for each block: 1.5k–15k–55k–10k) was synthesized by reversible additional fragmentation transfer (RAFT) emulsion polymerization using amphiphilic macro‐RAFT agent [poly(acrylic acid)₂₀‐b‐polystyrene₅ trithiocarbonate] as both reactive surfactant and polymerization mediator. It was found that the ASIS nanoparticles were able to self‐assemble on oil/water interface to stabilize Pickering emulsion of hexadecane in the pH range from 8 to 12. The droplet diameter was finely tuned from 17 to 5 µm by increasing the ASIS particle levels from 0.13 to 12 wt % based on the mass of the ASIS aqueous dispersions. With toluene as a coalescing aid, the capsules with a coherent and nonporous shell were obtained with the dispersed phase volume percentage as high as 50%. The toluene treated capsules were so mechanically strong to survive the utrasonic treatment. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46700.     

A combined interfacial and in-situ polymerization strategy to construct well-defined core-shell epoxy-containing SiO2-based microcapsules with high encapsulation loading,super thermal stability and nonpolar solvent tolerance

SiO₂-based microcapsules containing hydrophobic molecules exhibited potential applications such as extrinsic self-healing, drug delivery, due to outstanding thermal and chemical stability of SiO₂. However, to construct SiO₂-based microcapsules with both high encapsulation loading and long-term structural stability is still a troublesome issue, limiting their further utilization. We herein design a single-batch route, a combined interfacial and in-situ polymerization strategy, to fabricate epoxy-containing SiO₂-based microcapsules with both high encapsulation loading and long-term structural stability. The final SiO₂-based microcapsules preserve high encapsulation loading of 85.7 wt% by controlling exclusively hydrolysis and condensed polymerization at oil/water interface in the initial interfacial polymerization step. In the subsequent in-situ polymerization step, the initial SiO₂-based microcapsules as seeds could efficiently harvest SiO₂ precursors and primary SiO₂ particles to finely tune the SiO₂ wall thickness, thereby enhancing long-term structural stability of the final SiO₂-based microcapsules including high thermal stability with almost no any weight loss until 250°C, and strong tolerance against nonpolar solvents such as CCl₄ with almost unchanged core-shell structure and unchanged core weight after immersing into strong solvents for up to 5 days. These SiO₂-based microcapsules are extremely suited for processing them into anticorrosive coating in the presence of nonpolar solvents for self-healing application.     

Synthesis of Polystyrene/Hydrophobic SiO2 Composite Particles via Oil‐in‐Water Pickering Emulsion Polymerization

The aim of this work is to present a facile Pickering emulsion polymerization method for the synthesis of submicron polystyrene/SiO₂ core/shell composite particles. The commercial hydrophobic SiO₂ nanoparticles were used as stabilizing agent for creating a stable oil‐in‐water emulsion. Although the adsorption of hydrophobic SiO₂ nanoparticles in the emulsion system was unfavorable in terms of thermodynamics, by ultrasound treatment, self‐assembly of hydrophobic SiO₂ nanoparticles effectively stabilized oil‐in‐water Pickering emulsions during polymerization. Using 3 wt.% SiO₂ nanoparticles (based on styrene monomer) and 1:10 volume ratio of styrene monomer:water, the composite particles having average size of 790 nm and relatively narrow particles distribution were produced. With decreasing the volume ratio, smaller composite particles were created. Results from scanning electron microscope revealed that SiO₂ nanoparticles were located exclusively at the surface of the polystyrene latex particles. The SiO₂ content, determined by thermogravimetric analysis, was 12.6 wt.% in the composite particles. The route reported here may be used for the preparation of other composite nanostructures. POLYM. ENG. SCI., 59:E195–E199, 2019. © 2018 Society of Plastics Engineers     

Control of release characteristics in pH‐sensitive poly(vinyl alcohol)/poly(acrylic acid) microcapsules containing chemically treated alumina core

The pH‐sensitive poly(vinyl alcohol)/poly(acrylic acid) hydrogel microcapsules containing vitamin B₁₂‐loaded Al₂O₃ core were prepared with a three‐step emulsion polymerization. Al₂O₃ was chemically treated with HCl or NaOH solutions at room temperature for 24 h to modify the binding properties with vitamin B₁₂. The colon‐targeted release characteristics of vitamin B₁₂ from the microcapsules were evaluated at different pHs. These microcapsules showed the faster and larger release of vitamin B₁₂ due to the high swelling of microcapsule shell as the pH was changed into more basic condition. However, these microcapsules showed the slower and less release of vitamin B₁₂ as the acid value of Al₂O₃ increased due to the strong binding interaction between Al₂O₃ core and vitamin B₁₂ even though the initial loading of vitamin B₁₂ was higher. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study on the antimicrobial activities of the capsaicin microcapsules

In this study, capsaicin microcapsules were prepared by the complex coacervation of gelatin, acacia, and tannins. The antimicrobial activities of these microcapsules on the common microorganisms of food preservation, Botrytis cinerea and Aspergillus niger, were investigated. The factors affecting their antimicrobial effects, including the microcapsule concentrations, pH values, and release behavior were also examined. The results showed that the optimum pH for the antimicrobial effect was about 5.0, which might be related to the strongest protein‐precipitating ability of tannins at this pH value. The inhibitory activity of the system originated from the synergistic actions of both capsaicin and tannins. The release behavior of the microcapsules had an important influence on the antimicrobial effect for the long shelf‐life storage of foods. The present study indicated that the capsaicin microcapsules displayed potential antimicrobial applications in the food storage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1318–1321, 2006     

微胶囊制备技术及其聚合物基功能复合材料研究与应用进展

介绍了微胶囊中芯材与壁材的结构,以及对制备微胶囊所需条件和常用于制备微胶囊的芯材与壁材的物质。分析了常用的原位聚合法、界面聚合法、乳液聚合法、Pickering乳液聚合法、悬浮聚合法、种子微悬浮聚合法、掺杂种子微悬浮聚合法、聚合诱导相分离法和物理制备法共9种方法。介绍了微胶囊在相变储能、隐身、自润滑、自修复等功能材料中的应用。展望了微胶囊的应用前景。     

Preparation of polyacrylate/paraffin microcapsules and its application in prolonged release of fragrance

The purpose of the present work was to develop a fragrance encapsulation system using polyacrylate/paraffin microcapsules. The Polyacrylate/paraffin microcapsules were fabricated by the method of suspension polymerization in Pickering emulsion. Morphology, size distribution, and thermal resistance of polyacrylate/paraffin microcapsules were investigated by scanning electron microscopy, light scattering particle size analyzer, and thermogravimetric analyzer. Results indicated that the crosslinked PMMA/paraffin microcapsules and P(MMA‐co‐BMA)/paraffin microcapsules prepared under optimal conditions presented regular spherical shape and similar size distribution. The crosslinked P(MMA‐co‐BMA)/paraffin microcapsules exhibited better thermal stability, with a thermal resistance temperature up to 184 °C. Fragrance microcapsules were prepared by encapsulating fragrance into crosslinked P(MMA‐co‐BMA)/paraffin microcapsules. The prolonged release performance of fragrance microcapsules was measured by ultraviolet‐visible near‐infrared spectrophotometer. 63.9% fragrance was retained after exposing fragrance microcapsules in air for 3 months, and the fragrance continued to release over 96 h in surfactant solution (sodium lauryl sulfonate, 20 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44136.     

Fabrication of Thermally Stable Polysulfone Microcapsules Containing [EMIm][NTf2] Ionic Liquid for Enhancement of In Situ Self‐Lubrication Effect of Epoxy

Microcapsules containing an ionic liquid (IL) are potential candidate materials for preparing in situ self‐lubricating composites with excellent tribological properties. 1‐ethyl‐3‐methylimidazolium bis[(trifluoromethyl) sulfonyl]imide ([EMIm]NTf₂) IL encapsulated polysulphone microcapsules are synthesized. The mean diameter and wall thickness are about 128 μm and 10 μm, respectively. Microcapsules have excellent thermal stability, with a thermal degradation onset temperature of 440 °C compared to traditional lubricants‐loaded microcapsules. In situ self‐lubricating composites are prepared by incorporating the IL‐encapsulated microcapsules into epoxy matrix. When the concentration of the IL microcapsules is 20 wt%, the frictional coefficient and specific wear rate of composites are reduced by 66.7% and 64.9% under low sliding velocity and middling applied load conditions, respectively, as compared to the neat epoxy. The tribological behavior of the self‐lubricating composites is further assessed in different applied load and sliding velocity conditions. The in situ self‐lubricating mechanism of composites is proposed.

     

Developing Multi Stimuli‐Responsive Core/Shell Microcapsules to Control the Release of Volatile Compounds

Encapsulation of 2‐oxoacetates into poly(urea‐urethane) core/shell microcapsules allows the light‐induced controlled release of volatile compounds such as fragrances, plant volatiles, pheromones, or other semiochemicals. On exposure to UVA light, 2‐oxoacetates decompose to form a carbonyl compound together with CO₂ or CO, which can build overpressure inside the capsules that expands and/or cleaves the capsule wall to release its content. The influence of the structure and ratio of the polyisocyanates and diamines used for interfacial polymerization, as well as the composition of the capsule wall and the oil phase, are investigated by dynamic headspace analysis of the released volatile compounds to optimize the performance of the delivery system. The combination of a light‐induced release with the mechanical cleavage of the capsule gives access to multi stimuli‐responsive systems that selectively respond to the different triggers applied. Furthermore, the concept outlined in the present work is generally applicable to other photolabile precursors that generate a gas inside the capsules and thus release co‐encapsulated active molecules as a direct response to light.     

Fabrication of covalently-bonded polystyrene/SiO<Subscript>2</Subscript> composites by Pickering emulsion polymerization

Pickering emulsion polymerization has attracted considerable attention in material fabrication due to its unique surfactant-free character and versatile association of oil, water and particles for a large set of materials. In this study, SiO₂ modified with Methacryloxypropyltrimethoxysilane (MPTMS) was employed to prepare Pickering emulsion, and subsequently covalently-bonded polystyrene/SiO₂(PS/SiO₂) composites were synthesized by Oil-in-water Pickering emulsion polymerization. Optical micrograph, contact angle, thermogravimetric analysis (TGA), Fourier transform infrared spectra (FT-IR), scanning electron microscope (SEM) and dynamic laser scattering (DLS) were employed to characterize the modified SiO₂, Pickering emulsion and prepared composites. It was found that prepared composites possess ragged surface morphology and SiO₂ concentration has an important effect on the morphology of as-prepared composites. In addition, covalent bond between PS core and SiO₂ shell was evidenced by FT-IR.     

Preparation and characterization of polyurethane microcapsules containing n‐octadecane with styrene‐maleic anhydride as a surfactant by interfacial polycondensation

A series of polyurethane microcapsules containing a phase change material (PCM) of n‐octadecane was successfully synthesized by an interfacial polymerization in aqueous styrene‐maleic anhydride (SMA) dispersion with diethylene triamine (DETA) as a chain extender reacting with toluene‐2,4‐diisocyanate (TDI). The average diameter of microPCMs is in the range of 5–10 μm under the stirring speed of 3000–4000 rpm. Optical and SEM morphologies of microPCMs had ensured that the shell was regularly fabricated with the influence of SMA. FTIR results confirmed that the shell material was polyurethane and the SMA chains associated on core material reacted with TDI forming a part of shell material. The shell thickness was decreasing in the range of 0.31–0.55 μm with the molar ratio of DETA/TDI from 0.84 to 1.35 and the weight of core material increasing from 40 to 80% (wt %). By controlling the weight ratio of PCM as 40, 50, 60, 70, and 80% in microPCMs, it was found using DSC that the T_m and T_c of microPCMs were in the range of 29.8–31.0^oC and 21.1–22.0°C and an obvious phase change had been achieved nearly the same temperature range of that of PCM. The results from release curves of microPCM samples prepared by 1.4, 1.7, and 2.0 g of SMA indicated the release properties were affected by the amount of the dispersant, which attributed to the emulsion effect and shell polymerization structure. The above results suggest that the shell structure of microPCMs can be controlled and the properties of microPCMs determined by shell will perform proper practical usage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4996–5006, 2006     

Synthesis and characterization of paraffin/TiO2‐P(MMA‐co‐BA) phase change material microcapsules for thermal energy storage

Microcapsules based on a phase changing paraffin core and modified titanium dioxide–poly(methyl methacrylate‐co‐butyl acrylate) [P(MMA‐co‐BA)] hybrid shell were prepared via a Pickering emulsion method in this study. The microcapsules exhibit an irregularly spherical morphology with the size range of 3–24 µm. The addition of BA can enhance the toughness of the brittle polymer poly(methyl methacrylate) and improve the thermal reliability of the phase change microcapsules. The ratio of BA/MMA is in the range of 0.09–0.14, and the ratio of the monomer/paraffin is varied from 0.45 to 0.60. These microcapsules exhibit a well‐defined morphology and good thermal stability. The actual core content of the microcapsules reaches 36.09%, with an encapsulation efficiency of 73.07%. Furthermore, the prepared microcapsules present the high thermal reliability for latent‐heat storage and release after 2000 thermal cycles. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46447.     

Poly(L‐histidine)‐chitosan/alginate complex microcapsule as a novel drug delivery agent

Novel poly(L ‐histidine)‐chitosan/alginate complex microcapsules were prepared from biodegradable polymers poly(L ‐histidine) (PLHis) in the presence of chitosan at acetate buffer solution pH 4.6. Microcapsules obtained are spherical and well‐dispersed with a smooth surface and a narrow size distribution. The microcapsules can encapsulate the protein model drug hemoglobin (Hb) efficiently. The results show that the complex microcapsules with low, medium, or high molecular weight of chitosan (0.05%, w/v), the highest encapsulation efficiencies obtained are 91.3%, 85.9%, and 94.2% with loading efficiencies of 47.8%, 44.3%, and 39.7%, respectively. The release profiles indicate that Hb‐loaded microcapsules conform to first‐order release kinetic in whole procedure, and 84.8%, 71.4%, and 87.3% of Hb were released during 72‐h incubation in PBS pH6.8 for microcapsules with low, medium, and high molecular weight chitosan (0.05%, w/v), respectively. The results also indicate that particle size and drug loading efficiency have a significant influence on the release profile and encapsulation efficiency. Our results reveal that the PLHis‐chitosan/alginate complex microcapsules are able to encapsulate and release Hb and are potential carriers for protein drugs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Hybrid shell microcapsules containing isophorone diisocyanate with high thermal and chemical stability for autonomous self-healing of epoxy coatings

Silica-polyurea/polyuretane hybrid shell microcapsules (MCs) loaded with isophorone diisocyanate (IPDI) with long shelf-life and high thermal and chemical stability are prepared via emulsification followed by interfacial polymerization at the surface of oil droplets of the oil-in-water emulsion. The resultant MCs are aimed at self-healing performance in epoxy coatings. A commercially available, highly reactive polyisocyanate named tris(p-isocyanatophenyl) thiophosphate is successfully employed as shell forming agent, while triethoxyoctylsilane and hexadecyltrimethoxysilane (HDMS) are tested as “latent” active hydrogen sources. The resulting MCs display core–shell morphology, spherical shape with diameter of 5–20 μm, shell thickness ca. 1–2 μm, and an IPDI core fraction of 69 and 65 wt %, when HDMS and triethoxyoctylsilane are employed, respectively. MCs exhibit an increased thermal stability, comparing with pure IPDI, which makes them robust enough to resist the thermal cycles involved in the coating's preparation. Stability of MCs inside specific solvents and chemicals, their chemical composition and shelf-life as well as effect of MCs on the epoxy curing are evaluated by Fourier transformed infrared spectroscopy. MCs, remarkably, show excellent environment stability and a long shelf-life of more than 3.5 months. Their addition to an epoxy formulation is found to heal damaged zones in the epoxy coating, as shown by scanning electron microscopy and electrochemical impedance spectroscopy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48751.     

Preparation and characterization of polyurea/polyurethane double‐shell microcapsules containing butyl stearate through interfacial polymerization

Double‐shell microcapsules containing butyl stearate were prepared through interfacial polymerization. The outer shell is polyurea formed through polymerization of toluene‐2,4‐diisocyanate (TDI) and diethylene triamine, and the inner shell is polyurethane (PU) formed through polymerization of TDI and polypropylene glycol 2000 (PPG2000). Styrene maleic anhydride copolymer was used as emulsifier. The effects of core to monomer ratio and dosage of PPG2000 on core content and encapsulation efficiency of microcapsules were investigated. The core content has a maximum at core to monomer ratio of 3–4, and the encapsulation efficiency has a maximum value of 95% at core to monomer ratio of 2. The prepared microcapsules were smooth and compact and have an obvious latent heat of 85 J/g. The shell structure of microcapsules was polyurea and PU. The average diameter of the microcapsules was 1–5 μm. The stabilities of the double‐shell microcapsule, such as anti‐ethanol wash and antiheat properties are obviously improved than those of single‐shell microcapsule. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011