Preparation and characterization of polytetrafluoroethylene‐polyacrylate core–shell nanoparticles

Polytetrafluoroethylene (PTFE)‐polyacrylate core–shell nanoparticles were produced by using PTFE micropowder and acrylate via seeded emulsion polymerization in the presence of fluorosurfactant. The properties of emulsion under various polymerization conditions were investigated and optimized. The chemical composition of the PTFE‐polyacrylate nanoparticles was characterized by Fourier‐transform infrared spectrometry (FTIR). The particle size and core–shell structure of the resulting PTFE‐polyacrylate nanoparticles were confirmed by transmission electron microscopy (TEM). Wettability of the PTFE‐polyacrylate core–shell particles was higher than the pristine PTFE. The formation of this kind of PTFE‐polyacrylate core–shell nanoparticles could improve the compatibility of PTFE with other materials because PTFE is covered by polyacrylate shell, which make them promising in various fields. Copyright © 2007 John Wiley & Sons, Ltd.     

An emulsifier‐free core–shell polyacrylate/diacetone acrylamide emulsion with nano‐SiO2 for room temperature curable waterborne coatings

An emulsifier‐free core–shell polyacrylate emulsion, containing nano‐SiO₂ nanoparticles in the core and diacetone acrylamide (DAAM) in the shell, has been successfully prepared by emulsifier‐free seeded emulsion polymerization. The effects of reaction temperature, dropping time, nano‐SiO₂ and initiator contents, and variation of the composition of core monomers on the amount of coagulum, particle size, and monomer conversion have been investigated. The particle morphology and the distribution of emulsion particles have been measured by transmission electron microscopy (TEM) and dynamic light scattering. The keto‐carbonyl groups on the surface of the polyacrylate emulsion nanoparticles reacted with adipic dihydrazide (ADH) to form a film with a cross‐linked network structure at room temperature. Therefore, the emulsifier‐free core–shell emulsion could be used as a two‐component room temperature curable waterborne coating. It was also found that the properties of the coating were clearly superior after using the cross‐linker. Copyright © 2009 John Wiley & Sons, Ltd.     

聚氨酯/聚丙烯酸酯复合乳液粒子热力学平衡形态预测

以水性聚氨酯分散液为种子采用无皂乳液聚合新技术合成出了具有核壳结构的聚氨酯/聚丙烯酸酯（PU/PA）复合聚合物乳液。采用界面张力简化计算方法计算了聚合物与聚合物之间以及聚合物和水之间的界面张力,通过界面自由能变化最小的热力学判据对合成的复合乳液粒子的热力学平衡形态进行了预测。并利用透射电子显微镜观察和用接触角法测定的膜的表面极性对其进行了证实。结果表明：界面自由能变化的最小判据可以推广到PU/PA 体系,本文给出的界面张力的简化计算方法是可行的。     

Preparation and characterization of emulsifier-free core–shell interpenetrating polymer network-fluorinated polyacrylate latex particles

The emulsifier-free core–shell interpenetrating polymer network (IPN) fluorinated polyacrylate latex particles with fluorine rich in shell were prepared by emulsifier-free seeded emulsion polymerization with water as the reaction medium. The fluorinated copolymer could be fixed on the particle surface due to the formation of interpenetrating polymer network. The resultant core–shell particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS) analysis, Fourier transform infrared (FTIR) spectrometry, X-ray photoelectron spectroscopy (XPS) analysis and thermogravimetric analysis (TGA). The core–shell particles possessed very narrow monomodal particle size distributions. XPS analysis of the latex film displayed that perfluoroalkyl groups had the tendency to enrich at surface and there was a gradient concentration of fluorine in the structure of the latex film from the film–air interface to the film–glass interface. In addition, compared with the latex film of crosslinked polyacrylate prepared under the same condition, the emulsifier-free core–shell IPN-fluorinated polyacrylate latex film showed better thermal stability, higher contact angle and lower water uptake.     

Synthesis and characterization of emulsifier-free trilayer core–shell polysilsesquioxane/polyacrylate/poly(fluorinated acrylate) hybrid latex particles

The trilayer core–shell polysilsesquioxane/polyacrylate/poly(fluorinated acrylate) (PSQ/PA/PFA) hybrid latex particles are successfully prepared, using functional PSQ latex particles with reactive methacryloxypropyl groups synthesized by the hydrolysis and polycondensation of (3-methacryloxypropyl)trimethoxysilane in the presence of a reactive emulsifier as seeds. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and dynamic light scattering (DLS) confirm that the resultant hybrid latex particles have evident trilayer core–shell structure and a narrow size distribution. The Fourier transform infrared (FTIR) spectra show that fluorinated acrylate monomers are effectively involved in the emulsion copolymerization and formed the fluorine-containing hybrid latex particles. XPS analysis of the obtained hybrid latex film reveals that the intensity of fluorine signal in the film–air interface is higher than that in the film–glass interface. In addition, compared with pure polyacrylate latex film, the obtained fluorine-containing hybrid film shows higher hydrophobicity and thermal stability, and lower surface free energy.     

亚微米级聚苯乙烯/聚硅氧烷核壳粒子的制备及其应用

以乳液聚合制备的聚苯乙烯乳液为种子,加入甲基三甲氧基硅烷(MTMS)水解溶液进行缩聚反应,合成亚微米级聚苯乙烯/聚硅氧烷核壳粒子,并以此作为光散射剂添加至聚甲基丙烯酸甲酯(PMMA)树脂中,制备了光散射材料;考察了亚微米级核壳粒子添加在PMMA树脂中的分散性。结果表明:经过双螺杆剪切作用的挤出加工后,可以实现核壳粒子在PMMA树脂中的良好分散。核壳粒子可以大幅度提高PMMA的雾度,当聚苯乙烯/聚硅氧烷核壳粒子(NS82)的含量为1%时,制得的PMMA样片(厚度为2 mm)的雾度为89%,透光率为69%,有效光散射系数为61%。     

Preparation of core‐shell structured particle and its application in toughening PA6/PBT blends

Combining the excellent mechanical strengths of polyamide 6 (PA6) with the low water absorption of poly(butylene terephthalate) (PBT) was supposed to be a feasible way to prepare a high comprehensive performance material. However, the poor compatibility between PA6 and PBT resulted in low‐notched impact strength of PA6/PBT blends. Poly(n‐butyl acrylate)/poly(methyl methacrylate‐co‐methacrylic acid) (PBMMA), a core‐shell structured modifier with controlled particle sizes, was prepared by seed emulsion polymerization and confirmed by Transmission electron microscope (TEM). The PBMMA particles as toughening modifier and compatilizer were employed to toughen PA6/PBT blends. The notched impact strength of the PA6/PBT blends was significantly increased and the water absorption was reduced with the addition of PBMMA particles. With 23.0 wt% modifier loading, the notched impact strength of the blends was 25.66 kJ/m², which was 4.04 times higher than that of pure PA6/PBT. Meanwhile, the water absorption of the blends was only 1.3%, dropping 53.6% compared with pure PA6 and reducing by 26.6% than PA6/PBT. Scanning electron microscope results showed that the PBMMA particles were dispersed in the PA6/PBT blends homogeneously, and the toughening mechanism was the cavitation of rubber particles and shear yielding of the matrix. Thermo‐gravimetric analysis analysis demonstrated that the compatibility between PA6 and PBT was improved with the addition of core‐shell PBMMA particles. The core‐shell particles could be used as an effective modifier to achieve the high toughness and low water absorption for PA6/PBT blends. Copyright © 2016 John Wiley & Sons, Ltd.     

聚硅氧烷/丙烯酸酯核/壳复合胶乳的粒径分布与成核机理

通过种子乳液法合成出具有高有机硅含量核 壳结构的聚硅氧烷 丙烯酸酯复合粒子 .研究了聚合方法、乳化剂浓度、引发剂浓度、单体滴加速度等工艺条件对复合乳液粒径尺寸、分布与形态的影响 ,并对复合乳液的成核机理进行了探讨 .研究表明 ,乳化剂浓度对乳液粒子的粒径分布和形态、结构有显著影响 ,引发剂浓度增加将使粒子粒径减小 ;相对一次投料法 ,种子乳液法生成的粒子分布窄 ,具有明显核壳结构 ,通过壳层单体滴加速度可以控制粒子的粒径尺寸和分布 ;而壳层丙烯酸酯聚合物主要是在聚硅氧烷种子表面的“过渡层”聚合、富集而成 .     

Synthesis and characterization of dual‐responsive micrometer‐sized core‐shell composite polymer particles

Dual‐responsive micrometer‐sized core‐shell composite polymer particles were prepared by dispersion polymerization followed by seeded copolymerization. Polystyrene (PS) particles prepared by dispersion polymerization were used as core particles. N‐isopropyl acrylamide (NIPAM) and methacrylic acid (MAA) were used to induce dual‐responsive that is thermo‐ and pH‐responsive properties in the shell layer of composite polymer particles, prepared by seeded copolymerization with PS core particles. Temperature‐ and pH‐dependent adsorption behaviors of some macromolecules on composite polymer particles indicate that produced composite polymer particles exhibit dual‐responsive surface properties. Copyright © 2007 John Wiley & Sons, Ltd.     

Fabrication of monodisperse luminescent nanoparticles with core/shell poly(styrene/thiophene) structure

Luminescent poly(styrene/thiophene) (PSt/PT) core/shell nanoparticles were prepared by oxidative polymerization in the presence of PSt seed particles. PSt seed particles with uniform size distribution were prepared with an anionic surfactant by an emulsion polymerization process, and were used as a template to prepare monodispersive PT‐coated nanoparticles. A luminescent Polythiophene (PT) layer was formed on the surface of PSt nanoparticles by oxidation polymerization with iron chloride (FeCl₃) and hydrogen peroxide (H₂O₂). The mechanism of core/shell formation was found to be the interface‐dominant polymerization induced by the electrostatic attraction between the sulfonate group of anionic surfactant and Fe³⁺ ions after the diffusion of thiophene monomer to the PSt nanoparticles. Field‐emission scanning electron microscopy and transmission electron microscopy (TEM) proved the core/shell structure, which provided key evidence that PT was incorporated onto the surface of PSt nanoparticles. In addition, the effect of the PT shell thickness on photoluminescent (PL) intensity was investigated by changing the shell thickness of PSt/PT nanoparticles. We observed that the PL intensity increased up to about 30 nm of PT shell thickness, and then decreased due to self‐absorption. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5968–5975, 2008     

Synthesis of poly(styrene-co-3-trimethoxysilyl propyl methacrylate) microspheres coated with polysiloxane layer

A procedure has been developed to coat micron-sized poly(styrene-co-3-trimethoxysilyl propyl methacrylate) microspheres with a smooth layer of polysiloxane by the hydrolysis and condensation of methyl trimethoxylsilane (MTMS). Firstly, polystyrene microspheres containing silanol groups were prepared by conventional dispersion polymerization using 3-(trimethoxysilyl) propyl methacrylate (MPS) as a functional comonomer in an ethanol/water medium. Secondly, the synthesis of the polysiloxane shell was carried out using a sol–gel process of MTMS. The thickness of the shells can be easily varied with different copolymer seeds and MTMS feed ratio. When we used copolymer particles with 2.00 μm diameter as seeds, the thickness of the polysiloxane shells can be varied from 0.10 to 0.18 μm. The core/shell structure of the composite microspheres was characterized by transmission electron microscope (TEM).     

纳米SiO_2/含氟丙烯酸酯共聚物复合乳液的制备与性能及聚合动力学研究

采用原位聚合法制备纳米SiO2/含氟丙烯酸酯共聚物复合乳液,研究了其聚合反应动力学,并通过红外光谱(IR)、透射电子显微镜(TEM)、热失重(TGA)等方法表征所得产物的结构及形态、乳胶膜的耐热性能和表面性能.研究结果显示,聚合反应的表观活化能为83.15 kJ/mol,纳米SiO2/含氟丙烯酸酯共聚物复合粒子呈现出明显的核壳结构,纳米SiO2粒子的引入不仅改善了聚合物的耐热性能,也在一定程度上提高了乳胶膜的抗水性.对膜表面自由能的组成分析表明,与一般含氟乳胶膜的表面自由能的情况相反,该乳胶膜的表面能是由较大的极性部分和较小的色散部分组成.     

聚氨酯/聚丙烯酸酯复合乳液的研制进展

概述聚氨酯－聚丙烯酸酯复合乳液的制备方法。特别对聚氨酯－聚丙烯酸酯复合乳液共聚法作了较为系统的介绍和讨论。     

In situ synthesis of polystyrene/nano-CdSe core/shell microspheres in aqueous solution at room temperature

Polystyrene/nano-CdSe (PS/CdSe) core/shell microspheres were synthesized via in situ soap-free emulsion polymerization using various functional monomers such as 2-(dimethylamino)ethyl methacrylate, 1-vinylimidazole, 2-vinylpridine, and 4-vinylpridine. They were co-polymerized with styrene monomer and provided the location for coordinating with Cd²⁺ ions on the PS particle surfaces. Then, we used an alkaline selenium solution as a selenium source. Reaction of the alkaline selenium solution with the previous emulsion produced nanocrystalline CdSe onto the surface of PS particles at room temperature under atmospheric pressure. The different kinds of functional monomers and the amount of both Cd²⁺ ion and functional monomer were playing important roles to obtain stable and uniform morphologies of CdSe particles. Morphological observations were carried out by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Through the SEM and TEM microphotographs, we could confirm the formation of PS/nano-CdSe composite particles. Ultraviolet–visible absorption measurement indicated the quantum dot effect in the resulted PS/nano-CdSe core/shell microspheres.     

Fe3O4/Polypyrrole/Au nanocomposites with core/shell/shell structure: synthesis, characterization, and their electrochemical properties

Uniform Fe3O4 nanospheres with a diameter of 100 nm were rapidly prepared using a microwave solvothermal method. Then Fe304/polypyrrole (PPy) composite nanospheres with well-defined core/shell structures were obtained through chemical oxidative polymerization of pyrrole in the presence of Fe3O4; the average thickness of the coating shell was about 25 nm. Furthermore, by means of electrostatic interactions, plentiful gold nanoparticles with a diameter of 15 nm were assembled on the surface of Fe3O4/PPy to get Fe3O4/PPy/Au core/shell/shell structure. The morphology, structure, and composition of the products were characterized by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The resultant nanocomposites not only have the magnetism of Fe3O4 nanoparticles that make the nanocomposites easily controlled by an external magnetic field but also have the good conductivity and excellent electrochemical and catalytic properties of PPy and Au nanoparticles. Furthermore, the nanocomposites showed excellent electrocatalytic activities to biospecies such as ascorbic acid (AA).     

Preparation of thermosensitive PNIPAM microcontainers and a versatile method to fabricate PNIPAM shell on particles with silica surface

Thermosensitive PNIPAM microcontainers were prepared by using silica particles as template. Silica particles were prepared by the St?ber method and surface modified with linear P(NIPAM-co-MPS) chains. PNIPAM shell was then fabricated on the P(NIPAM-co-MPS)-modified silica particles through precipitation polymerization of NIPAM and MBA. Finally, PNIPAM microcontainers were obtained by removing the silica cores with NaOH. The materials were characterized by TEM, FTIR, GPC, and DLS. The PNIPAM microcontainers exhibit good thermosensitivity. The method to fabricate thermosensitive PNIPAM shell can be generalized to a versatile method for preparing PNIPAM shell on particles with silica surface, which includes surface modification with P(NIPAM-co-MPS) and precipitation polymerization of NIPAM and MBA using the modified particles as seed. Through this method, PNIPAM shell was successfully fabricated on iron oxide/silica nanostructures with a wormlike shape and relatively large size, which demonstrates the versatility of the method.     

Synthesis of polytetrafluoroethylene/polyacrylate core-shell nanoparticles via emulsifier-free seeded emulsion polymerization

Polytetrafluoroethylene (PTFE)/polyacrylate core-shell nanoparticles were produced via the emulsifier-free seeded emulsion polymerization of acrylate monomers with PTFE latex as seed. The monomer conversions under different synthesis parameters were monitored by a gravimetric method. The polymerization conditions for preparing PTFE/polyacrylate core-shell nanoparticles were surveyed and optimized. The chemical component of the PTFE/polyacrylate particles was confirmed by comparing the Fourier-transform infrared spectra of PTFE and PTFE/polyacrylate particles. The core-shell structure of the resulting PTFE/polyacrylate nanocomposite particles was investigated by transmission electron microscopy. The water contact angles of the films prepared from PTFE/polyacrylate nanocomposite particles showed that the films were hydrophilic, which confirmed that polyacrylate covered the surface of the PTFE particles. This kind of PTFE/polyacrylate core-shell nanoparticles might advance the compatibility of PTFE with other materials due to the covering of the polyacrylate shell on the surface of PTFE, which would make them promising in various fields.     

反应性复合乳液的合成、表征及其交联反应

利用种子半连续乳液聚合方法合成了核层或壳层带有环氧基以及壳层带有羧基的3种不同核/壳结构的乳胶粒子,通过物理共混带环氧基和羧基的乳胶粒子,得到了两种反应性复合乳液.利用透射电镜和激光动态光散射对乳胶粒子进行了表征,其粒径分布较窄,粒径分布的多分散系数为0.062,平均粒径约76 nm,乳胶粒子具有明显的核/壳结构.通过胶膜的凝胶率和膨胀率的测定和红外光谱分析对反应性复合乳液中乳胶粒子的扩散及交联反应进行了研究,并探讨了不同核壳结构复合乳液对涂膜机械性能的影响.研究表明,当反应性复合乳液中的环氧基和羧基分别分布在乳胶粒子的核层和壳层时,有利于聚合物分子链的充分扩散和化学交联反应的进行,从而提高涂膜的物理化学性能,当甲基丙烯酸缩水甘油酯(GMA)含量为10 wt%时,涂膜的拉伸强度达20.3 MPa.     

Polar Gradient Latex Particles with Hydrophilic Core and Hydrophobic Shell Prepared via Multistep Emulsion Polymerization

Monodisperse polar gradient particles were synthesized via a three‐step emulsion polymerization using poly(butyl acrylate‐methyl methacrylate‐methacrylic acid‐ethylene glycol dimethacrylate) (P(BA‐MMA‐MAA‐EGDMA)) as core, poly(methyl methacrylate‐methacrylic acid‐styrene) (P(St‐MMA‐MAA)) as interlayer and polystyrene (PSt) as shell. The particle growth and encapsulation in each emulsion polymerization step were followed by transmission electron microscopy (TEM), dynamic light scattering (DLS) and conductometric titration. Results indicated that the feeding mode and the interlayer were essential to prepare the polar gradient latex particles with hydrophilic core and hydrophobic shell. The morphologies of the two‐layer core/interlayer and three‐layer core/interlayer/shell particles were observed in TEM micrographs, and the sequential encapsulations of the carboxyl‐containing core and the core/interlayer particles were confirmed by an increase in the particle size as well as an increase in the buried carboxyl percentage.     

Comparative study between core-shell and interpenetrating network structure polyurethane/polyacrylate composite emulsions

Anionic aqueous polyurethane dispersion was prepared by using carboxyl acid group to make the polyurethane dispersible, and then nanograde core-shell and crosslinked IPN structure polyurethane/polyacrylate composite latex (PUA) were synthesized by soap-free emulsion polymerization method with polyurethane dispersion as seed. FTIR, DSC, dynamic light scattering, TEM, ESCA, TGA, electronic tensile machine were employed to investigate the structures and properties of the composite latex and their polymers. Meanwhile the core-shell composite PUA emulsion and the crosslinked IPN composite PUA emulsion were compared. The results showed that the particle morphology of PUA composite emulsion is inverted core-shell structure with polyacrylate as the core and with polyurethane as the shell. The morphology of the crosslinked PUA emulsion was multi-core structure. The surface in core-shell PUA contains rich PU phase. The phase structure of the crosslinked PUA is more uniform. Three transition temperatures are observed for the core-shell composite PUA, two transitions are observed for the film from the crosslinked PUA. The TGA curves of core-shell PUA and crosslinked PUA exhibit two stages, the first stage corresponds to the thermal decomposition of hard segments in seed polyurethane; the second stage corresponds to the decomposition of soft segments in PUA and decomposition of polyacrylate. With the increase of glycidyl methacrylate (GMA) amounts in PUA composite emulsions, the tensile strength of the PUA films as well as the average diameter of the PUA composite emulsion particles increase, the elongation at break of the PUA films decreases.