原位乳液聚合制备的聚丙烯酸丁酯/纳米SiO2复合粒子的形貌和形成机理

通过吸附于水相分散纳米SiO2粒子表面的2,2'-偶氮(2-脒基丙烷)二氢氯化物(AIBA)的引发作用,进行丙烯酸丁酯(BA)的原位乳液聚合,制备聚丙烯酸丁酯(PBA)/纳米SiO2复合乳胶粒.分别采用透射电镜观察复合粒子的形貌,高速离心分离/超声分散和氢氟酸腐蚀表征复合胶乳中PBA乳胶粒与纳米SiO2粒子的结合程度.发现有纳米SiO2粒子聚集于复合乳胶粒表面,复合粒子表面粗糙,呈"草莓形"结构;当复合粒子中SiO2质量分率为14.6%～22.6%时,60%左右的纳米SiO2富集于复合粒子表面,30%左右被包覆在复合粒子内部,另有少量游离于水相.采用原位乳液聚合得到的复合粒子中纳米SiO2与聚合物的结合牢度远大于以AIBA为引发剂合成的PBA乳液与纳米SiO2分散液直接混合所能达到的结合牢度.认为在原位乳液聚合过程中,由于纳米SiO2粒子表面锚固的PBA量的不同,引起SiO2粒子的亲水/亲油性和与PBA的相容性也不相同,导致出现以上的SiO2的分布特性和复合粒子形貌.     

两步反相微乳液法原位制备纳米SiO2/聚甲基丙烯酸甲酯复合微粒

采用两步反相微乳液法原位聚合制备纳米SiO2／聚甲基丙烯酸甲酯(polymethylmethacrylate,PMMA)复合微粒。首先,通过混合2个分别增溶有2种反应物的微乳液,制备纳米SiO2粒子;然后,向混合后的微乳液中滴加单体及引发剂,通过单体的原位聚合反应得到SiO2,PMMA复合微粒。通过相图研究：确定了微乳液法制备复合微粒时初始组分的用量。通过透射电子显微镜、红外光谱、热重分析、X射线光电子能谱等手段对复合微粒进行了表征。结果表明：聚合后的PMMA包覆在SiO2表面．复合微粒的平均粒径为30nm．分散性良好。复合微粒中不能被抽提出来的聚合物占10．08％,这部分聚合物以Si-O-C键形式接枝在SiO2表面。     

纳米SiO_2表面接枝聚合改性及在PP中的分散

纳米SiO2粒子经硅烷偶联剂表面处理后,采用乳液聚合方法在纳米SiO2粒子表面接枝苯乙烯单体,实现了纳米SiO2表面的高分子包覆改性,制备了具有核壳结构的聚苯乙烯接枝SiO2复合纳米粒子.采用傅里叶变换红外光谱、透射电子显微镜对纳米SiO2粒子的表面结构及其在聚丙烯(PP)中的分散状况进行了表征.结果表明,接枝改性后纳米SiO2粒子能够在PP基体中均匀分散,明显改善了PP复合材料的力学性能.     

表面处理方式对纳米SiO2/PS复合粒子粒径及分布的影响

纳米SiO2粒子进行表面处理时所用表面活性剂的种类及用量直接影响二氧化硅/聚苯乙烯(SiO2/PS)复合粒子的粒径及分布。纳米SiO2粒子在超声波场作用下经十六烷基三甲基溴化胺(CTAB)处理后,可在纳米SiO2粒子表面形成单体和引发剂的富集区,在适当条件下引发以纳米SiO2粒子为核心的原位分散聚合反应。当纳米SiO2粒子对CTAB的吸附与初级粒子对聚乙烯吡咯烷酮(PVP)K-30的吸附达到动态平衡时,制备出的SiO2/PS复合粒子表面光滑,分散性好,仅有少量的游离纳米SiO2粒子存在,大部分纳米SiO2粒子被PS包裹。     

纳米SiO_2表面接枝甲基丙烯酸甲酯的研究

为了提高纳米二氧化硅(SiO2)粒子在阻燃型聚合物基纳米复合材料中的有效利用,需要对粒子的表面进行改性。此实验采用溶液聚合法,使甲基丙烯酸甲酯单体(MMA)在烷基化预处理的纳米SiO2粒子的表面进行接枝聚合,得到以纳米SiO2粒子为核、接枝聚甲基丙烯酸甲酯为壳的复合颗粒(SiO2-g-PMMA)。结果表明,PMMA以化学键成功地接到纳米SiO2的表面,并可通过改变接枝聚合的条件来调节粒子上所接聚甲基丙烯酸甲酯的结构,改性后的纳米SiO2粒子具有良好的热稳定性及分散性。     

有机-无机纳米粒子复合乳液的合成研究

自制纳米SiO2溶胶,用硅烷偶联剂(乙烯基三乙氧基硅烷)进行表面处理,然后合成以纳米SiO2溶胶为核,聚苯乙烯、丙烯酸酯为壳的有机-无机复合乳液。实验研究了对无机纳米粒子表面处理时的最佳工艺条件:在处理SiO2溶胶时,温度为80℃左右,时间24h以上。实验还探讨了聚合条件的选择及聚合过程的分析。最后对复合乳液的结构进行了表征。     

光固化纳米二氧化硅/环氧丙烯酸酯杂化涂料的制备与表征

通过在纳米SiO2粒子表面锚固热引发剂,然后在活性稀释单体中对纳米SiO2进行原位接枝聚合改性.将改性纳米SiO2和活性稀释单体的混合物直接与其他原料共混,制备了光固化纳米SiO2/环氧丙烯酸酯(EA)杂化涂料.采用傅立叶变换红外光谱(FTIR)、扫描电镜(SEM)、热重分析(TG)和涂膜性能试验等对杂化涂料的结构与性能进行了研究.结果表明,聚合物链段通过化学键接枝到了纳米SiO2粒子表面;改性后的纳米SiO2在杂化膜中分散良好;在引入改性纳米SiO2后,涂膜的耐热性、抗冲击性、硬度、附着力等性能得到显著改善.     

苯乙烯无皂乳液聚合接枝纳米TiO2的研究

采用无皂乳液聚合法，使苯乙烯单体（St）在烷基化预处理的纳米TiO2粒子的表面进行接枝聚合，得到了稳定的以纳米TiO2粒子为核、接枝聚苯乙烯为壳的复合颗粒（TiO2-g-PS）。研究了烷基化预处理以及聚合条件（单体浓度、引发剂浓度、反应时间）对TiO2表面接枝改性的影响，并对其聚合机理进行了探讨。结果表明：PS以化学键成功地接到纳米TiO2的表面，并且可以通过改变接枝聚合的条件来调节粒子上所接聚苯乙烯的结构，为进一步优化纳米粒子填充聚合物复合材料的结构和性能之间的关系建立基础。     

SiO2/聚氨酯纳米复合物的在位合成及其在环氧树脂中分散行为的研究

以水性阳离子聚氨酯纳米粒子为纳米微囊,利用原位水解法使正硅酸乙酯(TEOS)在囊内水解、聚合生成二氧化硅(SiO2)纳米粒子,从而合成出SiO2/聚氨酯纳米复合物的稳定水基乳液,实现纳米复合物中SiO2纳米粒子的均匀分散和良好的界面结合。并以此作为已表面改性的纳米粒子实现SiO2纳米粒子在环氧树脂的均匀分散。通过能谱扫描、透射电镜和乳液粒子粒径与分布等测试方式对含有环氧树脂的水性SiO2/聚氨酯纳米复合物进行测试。结果表明,SiO2/聚氨酯纳米复合物可以在环氧树脂中均匀分散且不团聚,同时也可促进环氧树脂在水中的分散。     

ATRP法制备纳米SiO2-g-PBA及其对POM改性

采用原子转移自由基聚合(ATRP)法在纳米二氧化硅(Si02)粒子表面接枝聚丙烯酸丁酯(PBA),产物为纳米siO2-g-PBA,采用透射电镜(TEM)、偏光电子显微镜(PLM)等手段研究了纳米SiO2及纳米SiO2-g-PBA复合粒子的添加对聚甲醛(POM)结晶性能及热稳定性的影响.结果表明.采用ATRP法有少量的PBA接枝了:纳米SiO2表面,且该粒子在POM中分散均匀;纳米SiO2及纳米SiO2-g-PBA复合粒子的添加不改变POM的晶型,但POM的晶粒尺寸变小.a纳米SiO2-g-PBA复合粒于的异相成核作用较纳米SiO2明显;纳米SiO02及纳米Si2-g-PBA复合粒子使POM的结晶温度升高,熔点升高,结晶度升高.纳米SiO2及纳米SiO2-g-PBA复合粒子的添加使得POM的热稳定性得到了提高.且纳米SiO2-g-PBA复合粒子的作用更明显.     

SCL@SiO2纳米颗粒制备及其稳定Pickering乳液的研究

用共轭亚油酸钠（SCL）在SiO2纳米颗粒表面吸附,得到表面改性的SiO2纳米颗粒,然后在80 oC条件下通过热聚合引发SCL分子自交联,从而稳定SCL@SiO2纳米颗粒的SCL层并改善表面润湿性。通过Zeta电位表征手段证实SCL吸附在SiO2纳米颗粒表面。以SCL@SiO2纳米颗粒作为单一乳化剂制备液体石蜡的Pickering乳液,结果表明该Pickering乳液比传统乳液更稳定。由于SCL@SiO2纳米颗粒的SCL层比简单吸附脂肪酸的SiO2改性颗粒更稳定,且粒径会随着pH的变化而发生变化,因此由其稳定的Pickering乳液具有一定的pH响应性。     

以SiO2纳米粒子为种子的甲基丙烯酸甲酯乳液聚合

本文采用SiO2纳米粒子作为种子进行了甲基丙烯酸甲酯的乳液聚合。初步探讨了此类种子乳液聚合的过程；也分析了SiO2的用量对所生成的残渣率的影响，SiO2在残渣中的实际含量均比在乳液聚合物中略高，这是由于总有一些单体转移到不含SiO2的自由胶束中进行聚合而造成的。所得的复合乳液聚合物的力学和热学性能测试结果表明材料的这两种性能均随SiO2含量的增加而降低。     

纳米粒子种类对PMMA／纳米复合材料性能的影响

研究了胶体SiO2、粉体SiO2、有机改性蒙脱土OMMT等不同纳米粒子种类对纳米复合材料性能的影响,通过红外光谱、X射线衍射、热重分析和动态力学性能等测试手段对复合材料进行了分析表征。结果表明,OMMT和胶体SiO2与聚甲基丙烯酸甲酯（PMMA）的复合效果最好;OMMT的加入对复合材料的热性能有一定提高,而胶体和粉体SiO2的加入提高了复合材料的储能模量。     

Synthesis of well-defined poly( n -vinylpyrrolidone)/n-TiO 2 nanocomposites by xanthate-mediated radical polymerization

For the first time formation of well-defined poly n-vinylpyrrolidone/n-TiO2 nanocomposite by xanthate-mediated radical polymerization was accomplished. The synthesis of polymer nanocomposite materials has been intensively studied due to their extraordinary properties and wide-spread potential applications. For this purpose, first 2‐propionic acid-O-ethyl xanthate, as a RAFT agent, was synthesized by the reaction of 2-bromopropionic acid with potassium O-ethyl xanthate with acetone as the solvent. A carboxylic group in the RAFT agent was attached to the n-TiO2 surface by metalation reaction. Then, RAFT polymerization of n-vinylpyrrolidone (NVP) was subsequently conducted to graft poly(n-vinylpyrrolidone) (PNVP) onto the exterior surface of n-TiO2 nanoparticles, forming a novel core–shell nanostructure with a mesoporous core and a polymeric nanoshell. The viscosimetry data and 1H NMR spectra were used to calculate the molecular weight of the polymer. The obtained results showed a good agreement withthe methods used. A significant enhancement in the stability of the composites was obtained as demonstrated by the TGA results. The SEM and TEM results showed that the polymer was formed on the surface of the particles. The XRD pattern of the nanoparticles of n-TiO2 presented the amorphous structure of the crystal morphology of the composites. The FTIR and UV–visible spectroscopy results proved that the PNVP chains were grafted onto the n-TiO2 nanoparticles by surface RAFT polymerization.     

Synthesis of poly(methyl methacrylate)/silica nanocomposite through emulsion polymerization using dimethylaminoethyl methacrylate

Polymer/Silica nanocomposite latex particles were prepared by emulsion polymerization of methyl methacrylate (MMA) with dimethylaminoethyl methacrylate (DM). The reaction was performed using a nonionic surfactant and in the presence of silica nanoparticles as the seed. The polymer‐coated silica nanoparticles with polymer content and number average particle sizes ranged from 32 to 93 wt % and 114–310 nm, respectively, were obtained depending on reaction conditions. Influences of some synthetic conditions such as MMA, DM, surfactant concentration, and the nature of initiator on the coating of the silica nanoparticles were studied. Electrostatic attraction between anionic surface of silica beads and cationic amino groups of DM is the main driving force for the formation of the nanocomposites. It was demonstrated that the ratio of DM/MMA is important factor in stability of the system. The particle size, polymer content, efficiency of the coating reaction, and morphology of resulted nanocomposite particles showed a dependence on the amount of the surfactant. Zeta potential measurements confirmed that the DM was located at the surface of the nanocomposites particles. Thermogravimeteric analysis indicated a relationship between the composition of polymer shell and polymer content of the nanocomposites. The nanocomposites were also characterized by FTIR and differential scanning calorimetry techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Facile fabrication of nanocomposite microspheres with polymer cores and magnetic shells by Pickering suspension polymerization

Pickering suspension polymerization was used to prepare magnetic polymer microspheres that have polymer cores enveloped by shells of magnetic nanoparticles. Styrene was emulsified in an aqueous dispersion of Fe₃O₄ nanoparticles using a high shear. The resultant Pickering oil-in-water (o/w) emulsion stabilized solely by magnetic nanoparticles was easily polymerized at 70 °C without stirring. Fe₃O₄ nanoparticles act as effective stabilizers during polymerization and as building blocks for creating the organic–inorganic hybrid nanocomposite after polymerization. The fabricated magnetic nanocomposites were characterized by FTIR, XRD, TGA, DSC, GPC, XPS and SEM. The structures of the polymer core and the nanoparticle shell were analyzed. We investigated the effects on the products of the weight of Fe₃O₄ nanoparticles used to stabilize the original Pickering emulsions. Pickering suspension polymerization provides a new route for the synthesis of a variety of hybrid nanocomposite microspheres with supracolloidal structures.     

Preparation and properties of poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)]/silica nanocomposite latex prepared using an acidic silica sol

BACKGROUND: Polyacrylate/silica nanocomposite latexes have been fabricated using blending methods with silica nanopowder, in situ polymerization with surface‐functionalized silica nanoparticles or sol–gel processes with silica precursors. But these approaches have the disadvantages of limited silica load, poor emulsion stability or poor film‐forming ability. RESULTS: In this work, poly[styrene‐co‐(butyl acrylate)‐co‐(acrylic acid)] [P(St‐BA‐AA)]/silica nanocomposite latexes and their dried films were prepared by adding an acidic silica sol to the emulsion polymerization stage. Morphological and rheological characterization shows that the silica nanoparticles are not encapsulated within polymer latex particles, but interact partially with polymer latex particles via hydrogen bonds between the silanol groups and the ? COOH groups at the surface of the polymer particles. The dried nanocomposite films have a better UV‐blocking ability than the pure polymer film, and retain their transparency even with a silica content up to 9.1 wt%. More interestingly, the hardness of the nanocomposite films increases markedly with increasing silica content, and the toughness of the films is not reduced at silica contents up to 33.3 wt%. An unexpected improvement of the solvent resistance of the nanocomposite films is also observed. CONCLUSION: Highly stable P(St‐BA‐AA)/silica nanocomposite latexes can be prepared with a wide range of silica content using an acidic silica sol. The dried nanocomposite films of these latexes exhibit simultaneous improvement of hardness and toughness even at high silica load, and enhanced solvent resistance, presumably resulting from hydrogen bond interactions between polymer chains and silica particles as well as silica aggregate/particle networks. Copyright © 2009 Society of Chemical Industry     

Preparation and characterization of TiO2 and polymer nanocomposite films with high refractive index

Novel nanocomposite films of TiO₂ nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol‐A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent‐resistance, good thermal stability, and mechanical properties were prepared by incorporating surface‐modified TiO₂ nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO₂ nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and long‐chain alkyl amines. These TiO₂ nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free‐standing films were obtained by drying a mixture of TiO₂ nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO₂ nanoparticles of 3–6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO₂ nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO₂ and poly(bisphenol‐A and epichlorohydrin) was in the range of 1.58–1.81 at 589 nm, which linearly increased with the content of TiO₂ nanoparticles from 0 to 80 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Chemical modification of TiO2 nanoparticles as an effective way for encapsulation in polyacrylic shell via emulsion polymerization

Encapsulation of inorganic nanoparticles by polymers is one of the interesting research topics that lead to the synthesis of nanocomposites. These nanocomposite materials comprise the properties of both organic polymer and inorganic nanoparticles. Here, hybrid latex particles with core–shell nanostructure were prepared via semi-batch emulsion polymerization. Copolymers of (methyl methacrylate-butyl acrylate) and (dimethylaminoethyl methacrylate-butyl acrylate-acrylic acid) were formed as the inner and outer layers, respectively on the surface of modified TiO₂ nanoparticles as the core. In order to create compatibility between inorganic and polymeric phases, modification of TiO₂ nanoparticles was performed with glycidyl methacrylate with an optimized procedure for the first time and then emulsion polymerization was carried out. The products of each step were fully characterized. The results of dynamic light scattering, TEM and SEM analyses proved the formation of encapsulated hybrid latex particles. DLS and SEM data revealed that the sizes of nanocomposite particles vary between 85 and 120 nm for 0–5 wt% of the modified TiO₂ nanoparticles. Physico-mechanical properties of the obtained nanocomposite films were studied by DMTA. It was found that using only 3 wt% of modified TiO₂ improved those properties of resulting films remarkably.