Encapsulation of TiO2 by emulsion polymerization with methyl metacrylate (MMA)

Summary This paper presents a methodology of encapsulation of TiO₂ (Titanium dioxide) by emulsion polymerization on the proposal to modify the physical-chemical properties of the pigment surface. In the proposed methodology the TiO₂ was previously modified by isopropoxy-titanium-tri-isostearate, before being encapsulated by emulsion polymerization using Methyl Methacrylate as monomer. The effects of the polymerization process, type of initiator and monomer concentration in the efficiency of encapsulation were studied. The encapsulated pigment was characterized by Thermogravimetric Analysis (TGA), Light Scattering (LS) and Transmission Electron Microscopy (TEM).     

无规甲基化β-环糊精对甲基丙烯酸甲酯无皂乳液聚合影响

采用溶液法制备了无规甲基化β-环糊精(RAMEB)/甲基丙烯酸甲酯(MMA)包合物,利用紫外-可见光谱、热重-差热分析等检测手段表明RAMEB与MMA可以形成摩尔比为1∶1的包合物,从而使MMA的热稳定性大大提高。通过RAMEB与MMA的包合作用研究了RAMEB对MMA无皂乳液聚合反应的影响。结果表明,当RAMEB的加入量为4.2×10-4mol时,体系在75℃反应30 min时,单体转化率达89.2%,比同一时间下没有加入RAMEB的空白样的单体转化率提高了30.6%。当RAMEB的加入量为8.4×10-4mol时,聚合反应速率比空白样低,单体的最终转化率与空白样差不多。同时,RAMEB的引入可以使PMMA微球粒径变大,随着RAMEB加入量的增加,聚合物微球的大小越来越均匀。     

AC对St或MMA为壳层单体种子乳液聚合的影响

在种子乳液聚合中加入发泡剂偶氮二甲酰胺(AC),制备了可发气核壳结构复合微球。探讨了AC用量对以聚苯乙烯(PSt)微凝胶为种子,St或甲基丙烯酸甲酯(MMA)为壳层单体的2种体系稳定性及转化率和反应速率的影响。结果表明,以MMA为壳层单体的聚合体系是较理想体系。当AC用量从1g增加到8g时,以St为壳层单体体系的最终转化率从96．2％下降到74．2％,以MMA为壳层单体体系的最终转化率基本不变,保持在96％左右。但AC的加入使以MMA为壳层单体体系的反应速度最大值的出现时间推后了10min,且其值仅为未加入AC体系的1／2左右。     

反应性乳化剂对MMA/BA乳液聚合的影响

将不同性质的反应性乳化剂应用于MMA／BA乳液聚合，对聚合过程的特性、乳胶粒子的大小和形态及乳液的性能进行了研究，发现不同性质的反应性乳化剂对无皂乳液聚合有不同的影响。     

聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子的制备

由种子乳液聚合法制备了聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子。以过硫酸钾(KPS)为引发剂,辛基酚聚氧乙烯醚(OP-10)为乳化剂,合成了聚苯乙烯(PS)种子核;连续滴加甲基丙烯酸甲酯(MMA),在核表面富集MMA,制备了粒径范围在0.16~0.67μm的核-壳粒子;当单体苯乙烯与甲基丙烯酸甲酯(St/MMA)的比为30∶70(质量比)时,所得粒径在0.18μm,粒径分布为0.012。差示扫描量热(DSC)研究显示,复合粒子的玻璃化转变温度(Tg)为97.2℃,峰形单一,表现出良好的热性能。     

甲基丙烯酸甲酯的乳液聚合

以甲基丙烯酸甲酯为主要原料,过硫酸铵为引发剂,OP-10和十二烷基苯磺酸钠(1∶1)为混合乳化剂,聚乙烯醇为分散剂,用乳液聚合的方法合成了聚甲基丙烯酸甲酯乳液.考察了产品的转化率、粒径、红外光谱、粘度及其热稳定性并进行了表征.与传统的聚合方法相比,该聚合方法具有乳液粒径小且分布均匀、聚合速度快、所获得的聚合物纯度较高以及合成的聚乳液可以直接应用等优点.     

Material encapsulation in poly(methyl methacrylate) shell: A review

Material encapsulation is a relatively new technique for coating a micro/nanosize particle or droplet with polymeric or inorganic shell. Encapsulation technology has many applications in various fields including drug delivery, cosmetic, agriculture, thermal energy storage, textile, and self-healing polymers. Poly(methyl methacrylate) (PMMA) is widely used as shell material in encapsulation due to its high chemical stability, biocompatibility, nontoxicity, and good mechanical properties. The main approach for micro/nanoencapsulation of materials using PMMA as shell comprises emulsion-based techniques such as emulsion polymerization and solvent evaporation from oil-in-water emulsion. In the present review, we first focus on the encapsulation techniques of liquid materials with PMMA shell by analyzing the effective processing parameters influencing the preparation of PMMA micro/nanocapsules. We then describe the morphology of PMMA capsules in emulsion systems according to thermodynamic relations. The techniques to investigation of mechanical properties of capsule shell and the release mechanisms of core material from PMMA capsules were also investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48039.     

制备负载无机纳米颗粒的形状规整的微囊

A facile and efficient method has been developed for microencapsulation of metal oxide nanoparticles in polyurea via interfacial polymerization of toluene-2,4-diisocyanate and H20 through the atomizing emulsification approach. The resultant microcapsules were well-shaped and uniform sphere with diameter ranging from 2 to 6 um. Thermogravimetry （TG） and differential scanning calorimetry （DSC） curves revealed that the microcapsules showed good thermal stability （no decomposition observed under 245℃）. Besides, the microencapsulated TiC2 has been used as an efficient catalyst for photocatalytic degradation of methyl orange. Furthermore, the photocatalysis of immobilized TiC2 could be enhanced by introducing UV absorbing agent to the wall of microcapsules.     

一种含磷阻垢分散剂的反相乳液合成及性能

研究了以环己烷为分散介质，油／水比例为1．5，Span80-Tween80为乳化剂，过氧化氢为引发剂，以丙烯酸（AA）、丙烯酰胺（AM）、甲基丙烯酸甲酯（MMA）和次亚磷酸钠（SH）为单体合成共聚物（AA—AM—MMA—SH）阻垢分散剂。通过静态阻垢实验评定该共聚物对水中CaCO3，Ca3（PO4）2，CaSO4的阻垢效果，探讨了药剂用量、恒温温度、溶液pH值、水体硬度等因素对阻垢性能的影响，及共聚物分散氧化铁的性能。并利用红外光谱（IR）法对其结构进行了表征。实验结果表明：合成的阻垢剂具有较好分散性能及耐高温，高硬度，宽pH值等优良阻垢性能。     

甲基丙烯酸甲酯的电化学乳液聚合

采用可编程的线性直流电源电解铁阳极产生Fe2+,以此引发过硫酸铵（APS）产生自由基,催化甲基丙烯酸甲酯（MMA）单体进行乳液聚合。在优化的聚合时间和引发剂浓度条件下,重点研究了电流强度对聚合物相对分子质量及分布的调控作用。结果表明：在0.10~0.18 A的电流范围内,随着电流强度的增大,聚合物的平均相对分子质量也有所增加。通过调节电流的大小,可以对聚合物的相对分子质量分布进行调控,当电流从0.10 A增大至0.12 A时,聚甲基丙烯酸甲酯（PMMA）相对分子质量分布指数（Mw/Mn）减小为1.461。     

微囊化技术进展及应用

介绍了微囊化技术的主要工艺方法。对无机亚微粒子的有机聚合物微囊化进行了讨论。结合笔者在采用乳液聚合法对钛酸酯修饰的ＴｉＯ２粒子所做的工作，提出了获得稳定的微囊化工艺的必要条件。介绍了微囊的应用前景。     

PMMA/BA无皂乳液聚合

以过硫酸铵为引发剂,用超声波引发PMMA/BA无皂乳液聚合;探讨了单体和引发剂的质量分数对单体转化率的影响,并对聚合物进行了FT-IR和TEM的表征。结果表明:PMMA/BA乳胶粒直径大约在100nm左右。     

甲基丙烯酸甲酯悬浮聚合工艺条件的研究

通过悬浮聚合法制取了聚甲基丙烯酸甲酯(PMMA)。主要研究了分散剂、引发剂、温度、搅拌速度以及水和单体的比对聚合物的影响。结果表明:当单体的量为12mL时,水和单体比为5∶1(体积比);引发剂的量为0.16g;分散剂的量为MgCl2:3mL、NaOH:6mL;温度控制在75~78℃,反应约1.5h;搅拌速度为250r/min的实验条件下,制得了颗粒均匀、透明度良好、产率较高的聚甲基丙烯酸甲酯。     

核壳型丙—苯乳液的制备研究

实验证明,根据粒子设计所制备的丙－苯乳液为核壳型复合乳液,且该乳液具有很好的结构稳定性。研究了乳化剂、引发剂、滴加速度等对聚合反应的影响。讨论了软、硬单体配比、丙烯酸含量及交联剂对涂膜性能的影响。     

乳液聚合技术最新研究进展

在简单介绍乳液聚合特点的基础上,重点对近几十年来乳液聚合中发展的新技术,如核/壳乳液聚合、互穿网络聚合、微乳液聚合、无皂乳液聚合以及其它的一些新型乳液聚合方法进行了综述。     

Preparation of poly(methyl methacrylate)/titanium oxide composite particles via in‐situ emulsion polymerization

Poly(methyl methacrylate) (PMMA)/Titanium oxide (TiO₂) composite particles were prepared via in‐situ emulsion polymerization of MMA in the presence of TiO₂ particles. Before polymerization, the TiO₂ particles was modified by the silane coupling agent, which is crucial to ensure that PMMA reacts with TiO₂ via covalent bond bindings. The structure of the obtained PMMA/TiO₂ composite particles was characterized using Fourier transform infrared spectra (FTIR) and thermogravimetric analysis (TGA). The results indicate that there are covalent bond bindings between PMMA macromolecules and TiO₂ particles. Based on these facts, several factors affecting the resulting PMMA/TiO₂ composite system, such as the type of coupling agents, the mass ratio of the MMA to the modified TiO₂, the emulsifier concentration, and the initiator concentration, etc., were examined by the measurement of conversion of monomers, the gel content of polymers, the percentage of grafting, and the grafting efficiency, using gravity method or TGA method. As a result, the optimized recipe was achieved, and the percentage of grafting and the grafting efficiency could reach 216.86 and 96.64%, respectively. In addition, the obtained PMMA/TiO₂ composite particles were found to a stable colloidal dispersion in good solvent for PMMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4056–4063, 2006     

含［N,O］配体的镍配合物/烷基铝催化甲基丙烯酸甲酯的聚合

制备了两种镍配合物二［N-(2-氧基-1-萘甲醛)缩-2,6-二异丙基苯胺］合镍［Ni(L₁)₂］和二［N-(2-氧基-1-萘甲醛)缩-邻甲基苯胺］合镍［Ni(L₂)₂］。研究了它们以普通烷基铝为助催化剂催化甲基丙烯酸甲酯(MMA)的聚合。结果表明,镍配合物的结构、聚合条件如单体浓度、Al与Ni物质的量比、聚合温度和聚合时间等对甲基丙烯酸甲酯聚合反应活性有很大的影响，当甲基丙烯酸甲酯浓度为0.8 mol·L^-1、n(Al)∶n(Ni)=400、温度为0 ℃时,催化活性达到110.7 kg-PMMA·(mol-Ni·h)^-1。随着聚合时间的延长，催化活性下降，而转化率则随着聚合时间的延长而缓慢增加。     

Synthesis and characterization of submicron PMMA particles containing rare earth ions on the surface

Emulsifier‐free emulsion polymerization was adopted to synthesize rare earth containing submicron polymer particles under microwave irradiation. To control the size and distribution of the particle, the relationship between reaction time, monomer content, and particle radius was studied for the polymerization of methyl methacrylate (MMA) in the absence and presence of rare earth ions, in which water was used as solvent, and potassium persulfate was used as initiator. In the latter polymerization, the solution of MMA and europium octanoate (EOA) was used instead of MMA itself as EOA can be dissolved in MMA within certain concentrations, and the result shows that the polymerization process is affected by existence of EOA except when the amount of MMA is 2 ml. For particles containing rare earth ions, characterization shows that mole percentage of Eu(III) ion in the surface layer with a thickness of 5 nm, which is estimated from X‐ray photo electron spectroscopy (XPS), is always larger than the value estimated by inductively coupled plasma atomic emission spectrometer (ICP‐AES) for the whole particle, indicating that surface enrichment of rare earth ions took place during the polymerization. Further characterization by XPS depth measurement after Ar⁺ sputtering shows the same result. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1124–1131, 2003     

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。     

Morphology and thermodynamic analysis of composite polymer particles prepared by soap‐free emulsion polymerization in the presence of poly(methyl methacrylate) and polystyrene as biseeds

Biseeds emulsion polymerization was investigated with poly(methyl methacrylate) (PMMA) and polystyrene (PSt) as biseeds and styrene (St) as second‐stage monomer, as well as with thermodynamic analysis; namely, the principle of minimum interfacial free‐energy change was utilized to explain the competitiveness of different seeds for second‐stage monomer and the final equilibrium morphology of composite polymer particles. The experimental results indicated the polymeric particles prepared had bimodal size distribution and the PMMA seed particles showed a higher chance of obtaining St than that of the PSt seed particles, which was in agreement with the computational outcome by the principle of minimum interfacial free‐energy change. Owing to the kinetic factors, the equilibrium morphology could not be reached in the experiments. However, the results demonstrated that double or multiple seeds emulsion polymerization could be used as a model experiment to study the morphology of polymer particle and the morphological prediction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2675–2680, 2004