种子表面改性法制备核壳结构PSt/SiO_2复合微球

首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360nm的单分散聚苯乙烯(PSt)种子乳液,并以EtOH/H2O混合物为分散介质,利用γ-氨丙基三乙氧基硅烷(KH-550)在25℃下对PSt微球表面进行改性,得到了表面硅烷化并带有正电荷的改性PSt种子乳液,然后在碱性条件下加入原硅酸乙酯(TEOS)使其和微球进行共水解与共缩聚,制备出了核壳结构PSt/SiO2复合微球,并利用电镜对复合微球的结构形态进行了表征.研究表明,PSt种子乳液改性时体系的zeta电位随着KH-550用量的增加而升高,当KH-550用量为PSt种子重量的1/3时,体系的zeta电位从原来的-34.5mV升高到了38mV,达到对PSt微球表面改性的最佳值;在制备PSt/SiO2复合微球时,TEOS水解缩聚形成的SiO2包覆到改性微球上的量随着反应时间的延长而增加,反应24h时达到97.9%的最大值;随介质中水含量的增加,吸附到复合微球表面上的SiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比降低到60/28.5时,得到结构均一、壳层厚度为35nm的核壳结构PSt/SiO2复合微球。     

Pickering乳液聚合制备核-壳结构PS-SiO2复合微球

用二氯二甲基硅烷对纳米SiO2粒子进行疏水改性,当其表面Zeta电位由-54.8 mV变成-25.8 mV时,SiO2粒子就能在苯乙烯-水界面自组装,形成稳定的Pickering乳液,即以胶体粒子为乳化剂的乳液.利用Pickering乳液聚合制备了以聚苯乙烯(PS)为核、纳米SiO2为壳的PS-SiO2复合微球.用FT-IR、XPS、SEM、偏光显微镜等对复合微球进行了表征.结果表明:复合微球由聚苯乙烯和纳米二氧化硅粒子组成,二氧化硅粒子以单层、六方密排的方式分布在聚苯乙烯微球表面.     

二氧化硅-聚丙烯腈核-壳结构复合纳米粒子的制备与表征

以甲基丙烯酸-3-(三甲氧基硅基)丙酯改性的SiO2纳米粒子为种子,采用乳液聚合法制备了粒径分布较窄的SiO2-聚丙烯腈(SiO2-PAN)核-壳结构复合纳米粒子。采用动态光散射、傅里叶红外光谱、透射电镜和扫描电镜表征了复合纳米粒子的粒径及分布、组成、形态和结构,并研究了表面活性剂的加入方式、反应温度及交联剂的引入对制备SiO2-PAN复合纳米粒子的影响。结果表明:SiO2-PAN复合纳米粒子为核-壳结构。采用半连续加入表面活性剂的方法,可以成功抑制乳液聚合中次级粒子的生成。通过增加表面活性剂的初始加入量、加快表面活性剂的补加速率,或降低反应温度,可使SiO2-PAN复合纳米粒子的粒径变小。反应温度的降低以及交联剂的引入使SiO2-PAN复合纳米粒子的表面变得平滑。     

SiO2@P（MMA/BA/3FMA）复合纳米粒子的制备及膜性能

通过溶胶-凝胶法与半连续种子乳液聚合法相结合,以正硅酸乙酯(TEOS)制备的纳米SiO2为核,以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)和甲基丙烯酸三氟乙酯(3FMA)的共聚物P(MMA/BA/3FMA)为壳,合成了SiO2@P(MMA/BA/3FMA)核-壳结构纳米复合粒子.为防止纳米SiO2的团聚,提高其与共聚物的结合力,用乙烯基三甲氧基硅烷(VTMS)对纳米SiO2进行改性.通过红外光谱、透射电子显微镜、动态激光散射粒度仪、静态接触角测试仪、X射线光电子能谱分析和热重分析等表征了乳液结构及膜性能.结果表明,获得的复合纳米粒子呈现粒径分布为40～50 nm的核-壳结构球型颗粒.由于含氟官能团的迁移使得氟元素在膜-空气界面富集,有效降低了膜的表面自由能.当3FMA质量分数达到25%时,膜表面自由能达到最低值(23.13 mN/m).随着3FMA含量的增加,共聚物初始热分解温度由350℃提高到390℃.     

纳米SiO_2粒子锚固偶氮引发剂及接枝聚甲基丙烯酸甲酯

对纳米SiO2 粒子锚固偶氮引发剂 ,进而引发甲基丙烯酸甲酯聚合而制备聚甲基丙烯酸甲酯(PMMA) 纳米SiO2 复合粒子进行了研究 .纳米SiO2 先用环氧型硅烷偶联剂处理 ,再与偶氮二氰基戊酸发生缩合反应而锚固上偶氮引发剂 ,通过差示扫描量热和元素分析证明了引发剂在纳米SiO2 表面的锚固 .通过改性纳米SiO2 存在下MMA的乳液聚合 ,制备得到了接枝率为 2 3 2 %、接枝效率为 36 1%的PMMA 纳米SiO2 复合粒子 .经乳液聚合后 ,纳米SiO2 粒子团聚程度减小 ,在水相中分散稳定 .     

制备方法对模板法制备SiO_2中空微球形貌的影响

模板法是制备无机中空微球的重要方法之一.首先通过苯乙烯和甲基丙烯酸的无皂乳液聚合法制得表面含羧基、粒径为360nm的单分散聚苯乙烯(PSt)乳胶粒,并以此为模板,分别采用表面改性-前驱体水解法(PHC)和SiO2纳米颗粒层层自组装法(LBL),制备出了不同壳层厚度的PSt/SiO2核壳结构复合微球,然后经500℃煅烧4h,得到SiO2中空微球.利用透射电镜和扫描电镜对微球结构形态进行了表征.研究表明,首先利用γ-氨丙基三乙氧基硅烷(KH-550)对PSt模板微球进行表面改性、然后再在乙醇-水混合介质中进行原硅酸乙酯(TEOS)水解与缩合反应的PHC法,是制备PSt/SiO2核壳结构复合微球的简便方法,复合微球经煅烧可制得表面均匀、结构致密、壳层厚度和形貌可控的SiO2中空微球;而LBL法制备PSt/SiO2核壳结构复合微球的工艺复杂,煅烧后所得SiO2中空微球结构疏松,易于破碎.     

pH值和前驱体用量对核壳结构PSt/SiO2复合微球结构形态的影响

首先通过无皂乳液聚合法制得表面含羧基、粒径为360 nm的单分散聚苯乙烯(PSt)种子乳液,并在EtOH/H2O混合介质中用γ-氨丙基三乙氧基硅烷(KH-550)对其进行改性,制得表面含有活性硅乙氧基并带有正电荷的改性PSt乳胶粒,然后再加入原硅酸乙酯(TEOS)进行共水解与共缩聚反应,制备出了核壳结构PSt/SiO2...     

种子乳胶粒表面修饰法制备核壳结构PSt/TiO_2复合微球

首先采用无皂乳液聚合法合成了表面带负电荷、粒径为360 nm的单分散聚苯乙烯(PSt)乳液,并利用聚乙烯亚胺(PEI)在25℃下对PSt乳胶粒表面进行修饰,得到了表面带有正电荷的PSt种子乳液;然后以乙醇和水的混合物为反应介质,采用种子乳液加入法,使钛酸正丁酯(TBT)在修饰后的乳胶粒表面进行水解与缩合,制备出了核壳结构PSt/TiO2复合微球,利用电镜对复合微球的结构形态进行了表征.结果表明,PSt乳液改性时体系的zeta电位随着PEI用量的增加而升高,当PEI用量为PSt聚合物重量的15%时,体系的zeta电位从原来的-40.3 mV升高到了38.3 mV,达到对PSt乳胶粒表面改性的最佳值;在制备PSt/TiO2复合微球时,TiO2包覆量随着反应时间的延长而增加,反应7 h时达到90.2%的最大值;随介质中水含量的增加,吸附到复合微球表面上的TiO2纳米颗粒逐渐减少,复合微球表面逐渐变得光滑,当EtOH/H2O质量比为100/6.0时,得到结构均一、壳层厚度为29 nm的核壳结构PSt/TiO2复合微球.     

钛酸四丁酯水解制备聚苯乙烯/二氧化钛核壳粒子及空心二氧化钛微球

通过无皂乳液聚合方法制备了阳离子型及阴离子型聚苯乙烯(PSt)乳胶粒,并对后者用γ-氨丙基三乙氧基硅烷(KH550)进行了表面改性制得了乳胶粒表面载正电荷的乳液.在乙醇与水的混合溶剂中,分别使用以上3种PSt乳胶粒为核加入钛酸四丁酯制备了核壳型PSt/TiO2复合粒子.结果显示,仅在使用经KH550改性的阴离子PSt乳...     

SiO2/聚甲基丙烯酸叔丁酯核壳复合微粒的制备与表征

以甲基丙烯酸-3-(三甲氧基硅基)丙酯(MPS)修饰的SiO2胶体粒子为种子,甲基丙烯酸叔丁酯(tBMA)为单体、十二烷基硫酸钠(SDS)为乳化剂,采用种子乳液聚合法制备了SiO2/聚甲基丙烯酸叔丁酯的核壳复合微粒。微粒经水解后形成具有pH敏感性的无机/有机复合微粒。研究了影响核壳复合微粒形态结构的因素,结果发现,控制SiO2种子乳液的质量分数在1.5%～2%,可避免聚合过程中生成纯聚甲基丙烯酸叔丁酯乳胶粒子;反应体系中乳化剂SDS的用量超过质量分数0.3%时,易形成纯聚合物乳胶粒子;SDS用量低于质量分数0.15%时,生成的核壳复合微粒易产生团聚;单体和交联剂用量升高,核壳复合微粒的壳层厚度增加,用量过高会导致核壳复合微粒出现团聚现象,并且有纯聚合物乳胶粒子生成。采用TEM、NMR和FTIR及接触角测试技术分析结果表明,复合微粒是由SiO和聚甲基丙烯酸叔丁酯组成的核壳结构微粒。     

Synthesis of composite particles through emulsion polymerization based on silica/fluoroacrylate-siloxane using anionic reactive and nonionic surfactants

The composite particles with core/shell structure resulting from the combination of silica seed and hydrophobic copolymer (dodecafluoroheptyl methacrylate (DFMA), gamma-methacryloxypropyltriisopropoxidesilane (MAPTIPS), methyl methacrylate, butyl acrylate) were synthesized by emulsion polymerization. The amount of the silica seeds, concentration of reactive surfactant, as well as the addition of DFMA and MAPTIPS, have strong influences on the morphology of composite particles. It has been shown that it would be possible to produce stable organic/inorganic composite particles with inhomogeneous core/shell structure encapsulated by hydrophobic fluorinated acrylate even though using unmodified silica particles and admixture of anionic and nonionic surfactants. However, there was an obvious difference on the morphologies of core-shell structure whether the DFMA and MAPTIPS were added or not. It was concluded that two kinds of polymerization approaches might coexist in the presence of DFMA and MAPTIPS for raw silica. One clear advantage of this process is that there is only one silica bead for each composite particle. This kind of stable core-shell structural hybrid latex is useful for preparing high performance hydrophobic coating.     

Anchoring of polyacrylate onto silica and formation of polyacrylate/silica nanocomposite particles via in situ emulsion polymerization

Polyacrylate/silica nanocomposite latex particles were prepared by in situ emulsion polymerization of acrylate monomers initiated by 2,2′-azobis(2-amidinopropane)dihydrochloride (AIBA) adsorbed by silica nanoparticles. The anchoring of polyacrylate (ACR) onto silica nanoparticles was achieved through the physical absorption and chemical grafting reaction. The elution and HF etching experiments showed that most silica nanoparticles were encapsulated by ACR to form the raspberry-like ACR/silica nanocomposite latex particles. The silica nanoparticles with a greater grafting degree of ACR tended to locate in the bulk of the polymer, and the silica particle with a lower grafting degree would not be combined with polymer latex particles and always remained in water phase. The formation of the final ACR/silica nanocomposite latex particles included the anchoring of ACR onto silica primary particles, aggregation of silica primary particles to form the silica-containing latex particles, and the growth of latex particles.     

In Situ Semibatch Emulsion Polymerization of 2‐Ethyl Hexyl Acrylate/n‐Butyl Acrylate/Methyl Methacrylate/Cellulose Nanocrystal Nanocomposites for Adhesive Applications

Cellulose nanocrystals (CNCs) are safe, “green,” hydrophilic nanoparticles. CNCs are added in situ during a semibatch 2‐ethyl hexyl acrylate (EHA)/n‐butyl acrylate (BA)/methyl methacrylate (MMA) emulsion polymerization. As EHA is a more hydrophobic monomer, manipulation of the monomer feed composition allows for the evaluation of the effect of hydrophobicity on CNC distribution in the nanocomposite and ultimately on adhesive properties. The adhesive properties (loop tack, peel strength, and shear strength) of three different EHA/BA/MMA latex formulations are shown to simultaneously improve with increasing CNC loading. However, the hydrophobicity of the EHA leads to a nonuniform distribution of CNCs in the latex films. Comparison of the in situ polymerized nanocomposites to their blended counterparts is also made.     

Preparation of poly (styrene-methyl methacrylate)/SiO2 composite nanoparticles via emulsion polymerization. An investigation into the compatiblization

Inorganic/organic nanocomposite systems, in which inorganic particles are encapsulated into the polymer matrix, are new classes of polymeric materials. These materials combine the properties of both components. It means that polymer component with excellent optical property, flexibility and toughness could improve the brittleness of inorganic particles and besides, inorganic particles could increase the strength and modulus of polymers. There are various methods to make these inorganic/organic nanocomposites. One of them is the chemical process, in which polymerization is performed directly in the presence of the inorganic particles. Examples of miniemulsion, suspension or dispersion polymerization can be found in the literature but emulsion polymerization is by far the technique most frequently used.In this work, latex containing nanostructure hybrid of copolymer (styrene, methyl methacrylate, acrylic acid) and inorganic nanoparticles (silica) with core/shell structure was prepared via semi-batch emulsion polymerization. At first, silica nanoparticles were dispersed in water phase in an ultrasound bath to prevent the aggregation of nanoparticles, and then emulsion polymerization was performed in the presence of silica nanoparticles. Related tests and analysis confirmed the success in synthesis of nanostructure hybrids. Induced coupled plasma (ICP) analysis and thermal gravimetric analysis (TGA) showed the presence and amount of silica nanoparticles in the final latex. Dynamic light scattering (DLS) analysis confirmed the presence of 25-35 nm particles in the system and transmission electron microscopy (TEM) showed the core/shell morphology of nanoparticles. It has been shown that with an appropriate surfactant, adjusting the pH of media, using suitable monomers and under controlled conditions, it would be possible to produce stable organic/inorganic composite nanoparticles with core/shell structure. In another attempt and in order to investigate the effect of compatiblizing system, styrene-methyl methacrylate was copolymerized in the presence of modified silica particles with oleic acid as the inorganic dispersed phase at the same condition. Similar characterizations were performed in order to have a worthwhile comparison. The results for the late procedure show the effect of oleic acid in formation of aggregates as the core for polymeric nanocomposite particles.     

光致变色含氟丙烯酸酯涂层的制备及性能

选取十二烷基硫酸钠(SDS),辛基苯基聚氧乙烯醚(OP-10)为复合乳化剂,过硫酸钾(KPS)为引发剂,将2-(全氟己基)乙基甲基丙烯酸酯(PFM)与丙烯酸酯类单体采用预乳化-半连续种子乳液聚合法进行乳液共聚,再将羟基螺吡喃(SPOH)与乳液进行物理共混,制得光致变色含氟丙烯酸酯乳液。 通过多种表征手段研究丙烯酸正丁酯(n-BA)和甲基丙烯酸甲酯(MMA)软硬单体的质量比,SPOH的用量对聚合反应和乳胶膜性能的影响。 结果表明,加入含氟单体后乳胶膜与水、油的接触角提高,热稳定性提高;加入SPOH的质量分数为1.25%时,乳胶膜具有较好的光致变色性能。     

EFFECT OF THE PHASE STRUCTURE EVOLUTION ON THE PROPERTIES OF FILMS FORMED FROM PBA/P(St-co-MMA) COMPOSITE LATEX

A group of heterogeneous latexes poly(butyl acrylate)/poly(styrene-co-methyl methacrylate)(PBA/P(St-co-MMA)) were prepared by a semi-continuous seeded emulsion polymerization process under monomer starved conditions.The glass transition temperature(T_g)and the mechanical properties of the film formed from the composite latex changed with the evolution of the particle morphology.A photon transmission method was used to monitor the phase structure evolution of films which were prepared from core-shell PBA/...     

Synthesis of water-soluble hyperbranched polymer and its application in acrylic latex

A water-soluble hyperbranched polymer (WHBP), obtained from a second generation of hyperbranched polyester and maleic anhydride, was studied. Its effects on the properties of acrylic latexes, which were based on emulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA), acrylic acid (AA) and WHBP, and latex film were discussed. The characteristics of WHBP were determined by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared (FTIR) and gel permeation chromatography (GPC). Particle size and morphology of latex particles were confirmed by dynamic light scattering (DLS) and transmission electron microscope (TEM). The investigation showed that WHBP could be used in emulsion polymerization, and that latex of poly(BA-MMA-WHBP) was more stable than that of poly(BA-MMA-AA). The hardness of latex film increased from 2B to HB when WHBP was used.     

Designing superhydrophobic surface based on fluoropolymer–silica nanocomposite via RAFT‐mediated polymerization‐induced self‐assembly

Superhydrophobic surfaces (SHS) find versatile applications as coatings due to their very high water‐repellency, self‐cleaning, and anti‐icing properties. This investigation describes the preparation of a SHS from surfactant‐free hybrid fluoropolymer latex. In this case, reversible addition‐fragmentation chain transfer (RAFT) polymerization was adopted to prepare a copolymer of 4‐vinyl pyridine (4VP) and vinyl triethoxysilane (VTES), where the pyridine units were quaternized to make the copolymer soluble in water. The copolymer was further used as a macro‐RAFT agent to polymerize 2,2,2‐trifluoroethyl methacrylate (TFEMA) in a surfactant‐free emulsion via polymerization‐induced self‐assembly (PISA). The macro‐RAFT agent contained a small amount of VTES as co‐monomer which was utilized to graft silica nanoparticles (SNPs) onto the P(TFEMA) spheres. The film prepared using the nanocomposite latex exhibited a nano‐structured surface as observed by SEM and AFM analyses. Surface modification of the film with fluorinated trichlorosilane produced an SHS with a water contact angle (WCA) of 151.5°. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 266–275     

Synthesis and Characterization of Nano-silica/Polyacrylate Composite Emulsions by Sol-gel Method and in-situ Emulsion Polymerization

Organic nano-silica was firstly synthesized by sol-gel method with methyl methacrylate (MMA) and butyl acrylate (BA) in the micelles as dispersing media, tetraethoxysilicate (TEOS) as precursor, hydrochloric acid as catalyst and methacryloylpropyl trimethoxysilane (A174) as modifier. Subsequently, the nano-silica/polyacrylate composite emulsions were directly prepared by in-situ emulsion polymerization under the action of the initiator. The structure and properties were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic light-scattering (DSL), thermogracvimetry (TG) and transmission electron microscopy (TEM). The results showed that A174-modified nano-silica was successfully synthesized in the acrylate-based emulsions by the sol-gel method. The nano-silica was encapsulated by polyacrylate, and the composite latex particles exhibited an apparent core-shell structure. The A174 could improve the lipophilicity of nano-silica and increase the grafting efficiency of polyacrylate on nano-silica particles. The nano-silica/polyacrylate composite latex film had better thermal stability, and the composite latex particles had greater average size and broader size distribution in contrast to those of pure polyacrylate emulsions.     

Preparation of PDMS-ormosil and its application in miniemulsion polymerization

With the assistance of ultrasound, octamethylcyclotetrasiloxane (D4) and slight silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) were sufficiently mixed with silica sol, and the in situ ring-opening polymerization of D4 on the surface of silica nanoparticles, catalyzed by dodecylbenzene sulfonic acid (DBSA), was enhanced as well. Thus, polydimethylsiloxane (PDMS)-modified silica (PDMS-ormosil) mixture was obtained. A slight addition of silane coupling agent γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) could significantly enhance the modified efficiency. The PDMS-ormosil mixtures were directly dispersed in the mixed monomer methyl methacrylate and butyl methacrylate. Then, miniemulsion polymerizations of acrylate monomers containing PDMS-ormosils were carried out, with free PDMS as hydrophobe and neutralized DBSA as emulsifier, both preexisted in the PDMS-ormosil mixture. Thus, the troubles of separation, purification, and redispersion in the traditional techniques can be omitted. Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscope, scanning electron microscope, and water contact angle tests were utilized to demonstrate that nanocomposite particles with a core–shell structure were synthesized; when the silica content was 3 wt% of the monomers, the average particle size was 97 nm, and the generated PDMS improved the hydrophobicity of the nanocomposite latex.