核壳型纳米SiO2/含氟聚丙烯酸酯复合乳液的合成与表征

采用原位乳液聚合法,在可聚合阴离子乳化剂/非离子乳化剂复配体系下,以γ-甲基丙烯酰氧丙基三甲氧基硅烷(KH-570)改性的纳米SiO2、甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、丙烯酸(AA)等为核相组成,以MMA、BA及甲基丙烯酸十二氟庚酯(DFMA)为壳相单体,合成纳米SiO2/含氟聚丙烯酸酯复合乳液.考察了纳...     

Synthesis of ambient temperature self-crosslinking VTES-based core–shell polyacrylate emulsion via modified micro-emulsion polymerization process

Modified micro-emulsion polymerization was successfully used to synthesize a kind of ambient temperature self-crosslinking core–shell emulsion, consisting of polyacrylate core and vinyltriethoxysilane (VTES) modified polyacrylate shell, by varying the ratio of soft monomer (BA) and hard monomer (MMA) which is different in the core and shell. The emulsion and its film formed at ambient temperature were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Core–shell structure was clearly shown in TEM micrographs, and two distinct glass transition temperatures (T _g) were confirmed by DSC analysis. Lower T _g of core phase analyzed by DSC and self-crosslinking properties of VTES characterized by crosslinking degree cause latex particles form continuous film at ambient temperature. Thermal and mechanical properties and the surface properties of the latex films were also investigated. Results showed that the core–shell latex films containing 5 and 7.5 % VTES exhibited higher thermal stability, better mechanical properties, higher contact angle, and water resistance compared with pure polyacrylate film.     

壳层含硅的丙烯酸酯核壳乳液研究

以半连续滴加法制备壳层含γ-(甲基丙烯酰氧基 ) -丙基三甲氧基硅烷的丙烯酸酯核 -壳乳液。探讨了聚合条件对聚合反应的影响 ,并确定了最佳聚合条件。以红外光谱 (IR)、热分析仪 (TGA、DSC)、动态表面能分析仪、透射电子显微镜 (TEM)表征乳胶的性质及结构。     

Morphology and kinetic mechanism of facile one-step preparing TiO2/polyacrylate/TiO2 multilayer core–shell hybrid emulsion via miniemulsion polymerization

In this paper, we report a facile method for the preparation of TiO₂/polyacrylate/TiO₂ multilayer core–shell hybrid emulsion through polymerization. The chemical compositions of the copolymer were studied with Fourier transform infrared. TEM images reveal that nanocomposites show different core–shell structures with different TiO₂ contents. As the weight percentage of TiO₂ is 2 wt% (based on monomer, same below), there are no TiO₂ cores in some nanocomposites. When TiO₂ increases to 3 wt%, the TiO₂/polymer/TiO₂ multilayer core–shell composite particles are prepared. But the TiO₂ shells disappeared when the TiO₂ content kept increasing. TGA shows that the TiO₂ dispersed in latex films uniformly and the thermal stabilization improved with increasing TiO₂ contents. The effect of operating variables such as polymerization temperature and the concentrations of polymerizable emulsifier, initiator, extremely hydrophilic monomer, modified TiO₂ and HD on the kinetic behaviors was investigated. The formation mechanism of TiO₂/polymer/TiO₂ multilayer core–shell structure was inferred.     

纳米SiO2/聚氨酯-含氟丙烯酸酯杂化乳液的合成与表征

采用种子乳液聚合法,以聚氨酯（PU）乳液为种子（在聚合过程中为壳相）,甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）、甲基丙烯酸十二氟庚酯（DFMA）和γ-甲基丙烯酰氧丙基三甲氧基硅烷（KH-570）改性的纳米SiO₂组成的混合物为核相,合成了具有核壳结构的纳米SiO₂/聚氨酯-含氟丙烯酸酯（SiO₂/FPUA）复合乳液。考察了纳米SiO₂和DFMA用量对乳液聚合过程及乳胶膜性能的影响。通过傅里叶红外光谱（FT-IR）、接触角（CA）、透射电子显微镜（TEM）、热重（TG）、差示扫描量热仪（DSC）和力学性能测试（MPT）等表征乳液的结构形态、乳胶膜的表面性能和综合性能。结果表明：乳胶粒子呈现“反相核壳”结构,以聚丙烯酸酯（PA）相为核,PU相为壳;由于纳米SiO₂和DFMA的协同作用,涂膜的疏水性和综合性能得到了较大的提高。     

Efficient preparation of hybrid nanocomposite coatings based on poly(vinyl alcohol) and silane coupling agent modified TiO2 nanoparticles

In the present investigation, at first, the surface of titanium dioxide (TiO₂) nanoparticles was modified with γ-aminopropyltriethoxy silane as a coupling agent. Then a new kind of poly(vinyl alcohol)/titanium dioxide (PVA/TiO₂) nanocomposites coating with different modified TiO₂ loading were prepared under ultrasonic irradiation process. Finally, these nanocomposites coating were used for fabrication of PVA/TiO₂ films via solution casting method. The resulting nanocomposites were fully characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), thermogravimetric analysis/derivative thermal gravimetric (TGA/DTG), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TEM and SEM results indicated that the surface modified nanoparticles were dispersed homogeneously in PVA matrix on nanoscale and based on obtained results a possible mechanism was proposed for ultrasonic induced nanocomposite fabrication. TGA confirmed that the heat stability of the nanocomposite was improved. UV–vis spectroscopy was employed to evaluate the absorbance and transmittance behavior of the PVA/TiO₂ nanocomposite films in the wavelength range of 200–800 nm. The results showed that this type of films could be used as a coating to shield against UV light.     

改性纳米SiO2/聚氨酯-含氟丙烯酸酯无皂乳液合成及其胶膜性能表征

引言水性聚氨酯相对溶剂型聚氨酯具有不燃、气味小、不污染环境等优点[1-2],从而广泛用于涂料[3]、胶黏剂[4]、油墨[5]等领域。目前,常用于软包装领域的薄膜主要是表面能很低的非极性膜,而水性聚氨酯胶黏剂具有较高的表面自由能,对非极性膜的润湿性差,因此需要降低水性聚氨酯的表面张力,达到润湿非极性膜的目的。     

Surfactant-free core–shell hybrid latexes from soybean oil-based waterborne polyurethanes and poly(styrene-butyl acrylate)

Novel surfactant-free core–shell hybrid latexes have been successfully synthesized by seeded emulsion polymerization of 10–60 wt% vinyl monomers (styrene and butyl acrylate) in the presence of a soybean oil-based waterborne polyurethane (PU) dispersion as seed particles. The soybean oil-based waterborne polyurethanes, synthesized by reacting isophorone diisocyanate with methoxylated soybean oil polyols and dimethylol propionic acid, form the latex shell, serve as a polymeric high molecular weight emulsifier, while the vinyl polymers form the core. The structures and thermal and mechanical properties of the PU dispersions and the resulting core–shell latexes have been characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and measurement of the mechanical properties. The core–shell hybrid latex films show a significant increase in thermal stability and mechanical properties when compared with the pure polyurethane films, and exhibit a change in mechanical behavior from elastomeric polymers to tough and hard plastics, due to grafting and crosslinking in the hybrid latexes.     

Preparation and surface properties of core‐shell polyacrylate latex containing fluorine and silicon in the shell

The core‐shell polyacrylate latex particles containing fluorine and silicon in the shell were successfully synthesized by a seed emulsion polymerization, using methyl methacrylate (MMA) and butyl acrylate (BA) as main monomers, dodecafluoroheptyl methacrylate (DFMA), and γ‐(methacryloxy) propyltrimethoxy silane (KH‐570) as functional monomers. The influence of the amount of fluorine and silicon monomers on the emulsion polymerization process and the surface properties of the latex films were discussed, and the surface free energy of latex films were estimated using two different theoretical models. The emulsion and its films were characterized by particle size distribution (PSD) analysis, transmission electron microscopy (TEM), Fourier transform infrared spectrum (FTIR), nuclear magnetic resonance (¹H‐NMR and ¹⁹F‐NMR) spectrometry, contact angle (CA) and X‐ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and thermogravimetry (TG) analysis. The results indicate that the average particle size of the latex particles is about 160 nm and the PSD is narrow, the synthesized latex particles exist with core‐shell structure, and a gradient distribution of fluorine and silicon exist in the latex films. In addition, both the hydrophobicity and thermal stability of the latex films are greatly improved because of the enrichment of fluorine and silicon at the film‐air interface, and the surface free energy is as low as 15.4 mN/m, which is comparable to that of polytetrafluoroethylene (PTFE). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Inkjet printing of photocatalytically active TiO2 thin films from water based precursor solutions

In this work, aqueous chemical solution deposition route suited for inkjet printing is used for the synthesis of photocatalytically active TiO₂ coatings. Environmentally friendly precursor solutions with electromagnetic ink-jet printing, allows cheap and simple processing of TiO₂ films on glass. The hydrolysis reaction of water sensitive titanium alkoxide (Ti-alkoxide) precursor is controlled by adding complexing agents as citric acid and triethanolamine prior to water addition, and aqueous stable solutions are achieved. The pH of the solutions is brought to neutral to guarantee flexible processing, avoid damage to substrates and equipment. Solution parameters are adapted to obtain optimal gelation conditions and good jettability. The influence of processing parameters on the phase formation and surface morphology is studied by thermogravimetric analysis and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The photocatalytic activity of the films is evaluated by the degradation of methyl orange.     

n-BMA/MMA共聚核壳乳液的合成研究

通过半连续种子乳液聚合的方法,制备了具有核壳结构的丙烯酸酯聚合物乳胶粒子。采用甲基丙烯酸甲酯(MMA)、甲基丙烯酸酯正丁酯(n-BMA)等单体进行共聚。研究了共聚合过程中,乳化剂浓度、引发剂等对聚合物乳液粒径大小、凝胶量等的影响,并利用动态光散射(DLS)、透射电镜(TEM)和差示扫描量热仪(DSC)对乳胶粒子进行表征。结果表明:核乳液聚合阶段乳化剂浓度增大,乳液粒子的粒径变小,引发剂用量对粒径及分布影响不大;TEM观察到核乳胶粒径大小及变化趋势与DLS测得的结果相一致,并且核乳胶粒子和核壳乳液粒子都呈规则的圆球状,分布均一;DLS测试核壳丙烯酸酯乳胶粒子粒径的变化呈逐渐增长的趋势;DSC测试发现制备的核壳粒子有2个玻璃化转变温度(Tg),验证了胶乳粒子核壳结构的存在。     

微滴乳液聚合制备PDMS/SiO2纳米复合材料

采用超声分散的方法,以少量八甲基环四硅氧烷(D₄)对硅溶胶粒子进行表面接枝改性。然后在改性硅溶胶存在下,以十二烷基苯磺酸(DBSA)为乳化剂兼催化剂进行D₄的微滴乳液聚合,得到聚硅氧烷(PDMS)/二氧化硅(SiO₂)纳米复合乳液。采用FTIR、TGA、纳米粒度仪、TEM和拉力机分别对样品进行了表征。结果表明:采用超声分散的方法,能够有效地实现硅溶胶粒子的表面改性。通过微滴乳液聚合得到的复合乳胶粒是聚合物包覆二氧化硅粒子的核壳结构形态。SiO₂的引入提高了有机硅复合膜力学性能,增强了热稳定性。     

Polyacrylate‐core/TiO2‐shell nanocomposite particles prepared by in situ emulsion polymerization

We report the preparation of polyacrylate‐core/TiO₂‐shell nanocomposite particles through in situ emulsion polymerization in the presence of nano‐TiO₂ colloid obtained by the hydrolysis of titanium tetrachloride. The resultant colloidal system can be stable for months without any precipitation. In a typical sample, the diameter of nanocomposite particles was about 150 nm, and the thickness of TiO₂‐shell was 4–10 nm. Only cetyltrimethylammonium bromide was employed to provide the latex particles with positive charge, which was enough for the formation of fine TiO₂ coatings. Three initiators were tested. Ammonia persulfate was the most suitable one, because the cooperative effect was formed by the negatively charged TiO₂ particles and the terminal anionic group (SO₄^2?, the fraction of Ammonia persulfate) of the polymer chain on the surface of latex particles to maintain the stability of nanocomposite system. The pH value played a vital role in obtaining a tight TiO₂ coating. Transmission electron microscopy, X‐ray diffraction and Atomic force microscopy were used to characterize this nanocomposite material. It was found that rutile and anatase coexisted in the nanocomposite film. This may suggest a potential application in the field of photocatalytic coating. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1466–1470, 2006     

Electro-assisted preparation of dodecyltrimethoxysilane/TiO2 composite films for corrosion protection of AA2024-T3 (aluminum alloy)

Thin films of organosilanes have been successfully used as the alternative to toxic chromate coatings for surface pretreatment of metals and alloys. To further improve their corrosion performance, in the present work nano-scaled TiO₂ particles were added to the dodecyltrimethoxysilane (DTMS) films coated onto AA2024-T3 substrates, by using either the dip-coating or the cathodically electro-assisted deposition process. The obtained composite films were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle measurements, Fourier transform reflection-absorption IR (FTRA-IR) and electrochemical impedance spectroscopy (EIS). The results show that these two techniques (nanoparticles incorporation and the electro-assisted deposition) both facilitate the deposition process of silane films, giving thicker deposit and higher coverage surface along with higher roughness and hydrophobicity, and thereby improve their corrosion resistance. Moreover, the corrosion performance of silane films is further improved by the combined use of nanoparticles modification and electro-assisted deposition.     

Role of acrylic acid in the synthesis of core‐shell fluorine‐containing polyacrylate latex with spherical and plum blossom‐like morphology

The core‐shell fluorine‐containing polyacrylate latex was successfully synthesized by two‐stage semicontinuous emulsion copolymerization of methyl methacrylate (MMA), butylacrylate (BA), acrylic acid (AA), and dodecafluoroheptyl methacrylate (DFMA). The fluorine‐containing polyacrylate latex was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC). The effects of AA content on monomer conversion, polymerization stability, particle size, corsslinking degree, carboxyl groups distributions (latex surface, aqueous phase or buried in latex), as well as mechanical properties and water absorption rate of latex film were investigated. The obtained fluorine‐containing polyacrylate latex exhibited core‐shell structure with a particle size of 120–150 nm. The introduction of AA was beneficial for the increase of monomer conversion and the polymerization stability, and had little effects on the mechanical property of latex film. However, the hydrophilicity of AA made the water resistance of latex film get bad. With the increase of AA content, the carboxyl groups preferred to distribute on aqueous phase, and the possibility of homogeneous nucleation increased and more oligomers particles were formed. Moreover, the oligomers would distribute to the latex and continued to grow up, making the latex morphology changed from spherical to plum blossom‐like. The core‐shell latex had two T_g corresponding to the rubber polyacrylate core and hard fluorine‐containing polyacrylate shell, and the latex film possessed excellent thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42527.     

Structural and optical properties of ITO/TiO2 anti-reflective films for solar cell applications

Indium tin oxide (ITO) and titanium dioxide (TiO₂) anti-reflective coatings (ARCs) were deposited on a (100) P-type monocrystalline Si substrate by a radio-frequency (RF) magnetron sputtering. Polycrystalline ITO and anatase TiO₂ films were obtained at room temperature (RT). The thickness of ITO (60 to 64 nm) and TiO₂ (55 to 60 nm) films was optimized, considering the optical response in the 400- to 1,000-nm wavelength range. The deposited films were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). The XRD analysis showed preferential orientation along (211) and (222) for ITO and (200) and (211) for TiO₂ films. The XRD analysis showed that crystalline ITO/TiO₂ films could be formed at RT. The crystallite strain measurements showed compressive strain for ITO and TiO₂ films. The measured average optical reflectance was about 12% and 10% for the ITO and TiO₂ ARCs, respectively.     

Study on the properties of nano‐TiO2 particles modified silk fibroin porous films

Using the freeze‐drying method, Nano‐TiO₂/silk fibroin porous films were synthesized with different ratios of TiO₂ to silk fibroin solution. Through scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), tensile strain, and water‐solubility tests, the structures and properties of these porous films were characterized. The SEM results indicated that the pores of the nano‐TiO₂/silk fibroin porous films were uniformly distributed by the freeze‐drying method. The XRD analysis indicated that the formation of nano‐TiO₂ particles might induce a conformational transition of silk fibroin from the typical Silk I to the typical Silk II structure partly with an increase in the crystallinity of the porous films. Compared with the pure silk fibroin porous films, the mechanical properties of nano‐TiO₂/silk fibroin porous films were improved, and its heat transition temperature was also enhanced; however, the water‐solubility of this material was diminished. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The effect of the polymerization route on the amount of interphase in structured latex particles and their corresponding films

Three series of hard/soft styrene-acrylic latex based systems with equivalent compositions were prepared either by blending of homopolymer latexes or by preparing structured latex particles having core shell (CS) or inverted core shell (ICS) morphologies. Transmission electron microscopy (TEM) was used to investigate the particle morphologies, which were correlated to the calculated fractional radical penetration for the propagating species during the reactions. The thermo-mechanical properties as well as the morphology of the resulting latex films were analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and TEM. The viscoelastic properties of the interphase between the first and second-stage polymers formed in the structured hard/soft latex films, as well as its qualitative amount and also the film morphologies were found to depend on the interplay between thermodynamic and kinetic parameters during the synthesis of the samples.     

Preparation and properties of reactive polyurethane polyacrylate blends based on carbonyl‐hydrazide reaction

A new reactive polyurethane/polyacrylate (PU/PA) blend was developed by mixing a core–shell polyacrylate latex containing keto groups in shell layer and a polyurethane dispersion incorporating multiple hydrazide groups which was synthesized by introducing the poly‐hydrazide groups into the end of the vinyl‐terminated polyurethane chains. Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) results indicated that poly‐hydrazide groups had been incorporated in the polyurethane chains. Transmission electron microscopy (TEM) micrograph revealed that polyacrylate particles had a clear core–shell structure. The results of FTIR, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) indicated that the crosslinking reaction between two polymer systems had happened and crosslinking structure could effectively improve the compatibility between PA and PU. Thermogravimetric analysis (TGA) and mechanical tests results suggested that crosslinking structure could enhance the thermal stability and mechanical properties of blends. The influence of the PA content and the n(? CO? )/n(? NHNH₂) ratio on the hardness, water resistance, solvent resistance, and gel fraction of the blend films were comprehensively studied. The optimal PA content and n(? CO? )/n(? NHNH₂) ratio was 30% and 1.5:1 in this experiment, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44443.     

Carboxylic acid-functionalized, core-shell polystyrene@polypyrrole microspheres as platforms for the attachment of CdS nanoparticles

Polypyrrole-coated polystyrene latex particles bearing N-carboxyl functional groups (PS@PPyCOOH) were prepared by the in-situ copolymerization of pyrrole (Py) and the active carboxyl-functionalized pyrrole (PyCOOH) in the presence of 390 nm diameter-sized polystyrene (PS) latex particles. Uncoated PS particles were prepared by emulsion polymerization of styrene. The initial comonomer fractions (in mol%) were 25/75, 50/50, 75/25 and 100/0 for pyrrole and PyCOOH, respectively. The PS@PPyCOOH_x particles, where x stands for the initial molar fraction of PyCOOH (x = 0, 25, 50 or 75%), were characterized in terms of particle size, surface morphology, chemical composition and electrochemical redox activity using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), FTIR, TGA and cyclic voltammetry respectively. TEM showed an increase of the latex particle diameter after coating by the conducting polymer layer, from 390 nm for uncoated PS to 430 nm for PS@PPyCOOH₅₀ particles, allowing an estimation of the PPyCOOH shell thickness to 20 nm. FTIR and XPS detected PyCOOH repeat units at the surface of the latex particles, indicating that this monomer had indeed copolymerized with pyrrole. The core-shell structure of the PS@PPyCOOH_x particles was confirmed by etching the polystyrene core in THF, leading to the formation of hollow conducting polymer capsules. Positively charged CdS nanoparticles were electrostatically assembled onto the surface of PS@PPyCOOH₅₀ particles, as a function of pH. It was found that, contrarily to unfunctionalized PPy-coated latex particles, PS@PPyCOOH₅₀ particles could be evenly decorated with stabilized CdS nanoparticles, at pH 5.The films of the PS@PPyCOOH@CdS-coated ITO electrodes are shown to be electroactive and electrochemically stable.