Estimation of Morphology Characteristics of Porous Poly(propylene) Particles from Degassing Measurements

The transport of reaction species in polyolefin particles affects both the polymerization and the degassing of the powder in the down‐stream processing. The morphology of particles – that is, the distribution of polymer and pore phases – predetermines their degassing behavior. We utilize gravimetric measurements to obtain the dynamics of degassing and to determine morphology characteristics of porous poly(propylene) particles. We found that Fick's diffusion model is not generally capable of fitting the shape of degassing curves of porous particles. Therefore we propose a particle model including two sizes of compact polymer granules and demonstrate that the degassing can be described by this model and that the model is capable of estimating fractions of large and small compact zones and the size of large compact zones.

     

Spherical Polyolefin Particles from Olefin Polymerization in the Confined Geometry of Porous Hollow Silica Particles

Porous hollow silica particles (HSPs) are presented as new templates to control the product morphology in metallocene‐catalyzed olefin polymerization. By selectively immobilizing catalysts inside the micrometer‐sized porous hollow silica particles, the high hydraulic forces resulting from polymer growth within the confined geometries of the HSPs cause its supporting shell to break up from the inside. As the shape of the support is replicated during olefin polymerization, perfectly spherical product particles with very narrow size distribution can be achieved by using HSPs exhibiting a monomodal size distribution. Furthermore, the size of the obtained product particles can be controlled not only by the polymerization time but also by the size of the support material.

     

Synthesis of Latex Particles with Surface Functional Groups and Their Applications for the Fabrication of Porous Materials

In this study, monodisperse latex particles with specific surface functional groups were synthesized by emulsifier-free emulsion polymerization. Amidine or carboxylated polystyrene nanospheres with narrow size distribution were prepared by emulsion polymerization using AIBA (α,α′-zodiisobutyramidine dihydrochloride) as amine-containing initiator or acrylic acid as carboxyl-containing comonomer, respectively. Factors affecting the particle size and distribution were systemically studied by changing the amount of initiator or monomer, the polymerization temperature, and the stirring speed of emulsion polymerization reactor. Monodisperse polymethylmethacrylate beads were also synthesized by soapless emulsion polymerization using methacrylic acid or aminoethylmethacrylate hydrogen hydrochloride as comonomer for the surface functionalization of the particles. As applications of the latex beads, the polymeric particles were adopted as templating materials for the fabrication of macroporous titania film and meso-macroporous silica particles by colloidal templating method.     

X‐Ray Tomography Imaging of Porous Polyolefin Particles in an Electron Microscope

Advanced models of penetrant transport and reaction in spatially 3D porous polyolefin particles reconstructed from X‐ray µCT images require proper determination of particle morphology. Moreover, polyolefins exhibit a relatively low absorptivity for X‐rays, therefore their investigation using µCT can be difficult. In this paper, a low‐resolution µCT built into an SEM is used to examine how the µCT resolution and several user‐selected parameters associated with the scanning/reconstruction affect the resulting particle morphology. Using samples with known morphology and independent imaging techniques, the performance of the µCT device is critically assessed. Finally, a method suitable for the reliable reconstruction of polyolefin particles using low‐resolution µCT is proposed.

     

Characteristics of ZnO Particles Prepared by Au-catalyzed Phase Transport Technique

ZnO particles were prepared by Au-catalyzed vapor phase transport method on silicon substrate. Scanning electron microscopy(SEM) images show many ZnO particles were formed on the sample surface. They grew up layer by layer along the c-axis, which was confirmed by the results of X-ray diffraction(XRD). The morphology of ZnO particles is close to hemisphere and its formation process could be seen from the SEM image. The room temperature photoluminescence(PL) measurement revealed a narrow UV emission peak at 3.27 eV and a broad green emission peak at 2.45 eV, which was caused by the near-band-edge and deep-level emissions.     

Preparation and Application of Double Hydrophilic Block Copolymer Particles

The preparation of some unique block copolymers and block copolymer particles via radical heterophase polymerization is described. Special emphasis is placed on double hydrophilic block copolymers such as poly(styrene sulfonic acid)-b-poly(methacrylic acid) diblock copolymer and double hydrophilic block copolymer particles consisting of both hydrophilic shells and cross-linked hydrophilic cores. Examples are given for the application of such particles as adsorbents, nano-reactors for chemical synthesis, and as colloidal stabilizers in both heterophase polymerization and biomineralization reactions.     

碗形胶体颗粒/阵列薄膜的制备及性能研究进展

随着科学技术和应用需求的快速发展, 对胶体颗粒形貌、尺寸和组分提出了越来越高的要求, 简单组成的球形颗粒已经难以满足需求. 微/纳米碗形胶体颗粒/阵列薄膜由于具有比表面积大、结构对称性下降等特点, 在纳米反应器、药物运载、高灵敏度传感器、数据储存、自组装等方面有着广阔的应用前景, 其研究、开发和应用已经成为微／纳米材料研究领域的热点. 概述了近十年来国内外碗形胶体颗粒/碗形阵列薄膜的研究进展, 按照无机和金属、聚合物两大类分别对碗形材料的各种制备方法进行了详细介绍, 目前主要有单层胶体晶体模板法、碗形阵列薄膜模板法、诱导生长法、异形颗粒法、中空微球内陷法、种子聚合法、溶剂处理法等; 按照材质种类, 分别对TiO₂, ZnO, Fe_xO_y, 贵金属、聚合物等碗形颗粒/阵列薄膜的结构与性能研究进行了概述, 指出了其潜在的应用领域; 并进一步展望了该领域未来的发展趋势.     

Effect of matrix polymerization conditions on the structure and adsorption properties of porous polymers on the basis of divinylbenzene,acrylonitrile, and methyl methacrylate

A comparative study was carried out on the matrix polymerization of divinylbenzene, acrylonitrile, and methyl methacrylate in SBA-15 silica mesoporous molecular sieves. The occupancy of the matrix mesopores by the starting monomer, the medium, the polymerization temperature and time as well as the means of removing the exotemplate were all found to affect the spatial organization and porous structure of the polymer materials. Surplus occupancy of the mesopores by the monomer (1–1.5), polymerization in vacuum, and an alkaline method for matrix removal were found to be optimal. IR spectroscopy was used to find the conversion of the starting polymer by following the relative change in intensity of the vinyl group bands. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 6, pp. 371–375, November–December, 2008.     

Synthesis and characterization of hydroxy‐bisphosphonate micrometer‐sized particles by dispersion polymerization of a new styrylbisphosphonate monomer

Bisphosphonates (BPs) are nonhydrolyzable pyrophosphate (P‐O‐P) analogs possessing two phosphonate groups linked to a single carbon (P‐C‐P). The hydroxy‐bisphosphonates (hydroxyBPs) are obtained when the hydroxy group is also linked to this bridging carbon. Their ability to form bidentate or tridentate chelates with calcium ions results in a high affinity to hydroxyapatite (HAP) in dentin, enamel and bones. In this study, we designed and prepared crosslinked poly(styrylbisphosphonate) (PStBP) micrometer‐sized particles by dispersion polymerization of the styrylbisphosphonate (StBP) and ethylene glycol dimethacrylate (EDMA) monomers. The new StBP monomer was synthesized in an efficient one‐pot synthesis using tris(trimethylsilyl)phosphite as the phosphorus source followed by methanolysis. The StBP monomer was successfully isolated and characterized as tri‐sodium salt. Polymerization of the StBP monomer was carried out in two steps: in situ conversion of the tri‐sodium StBP monomer back to its acid form, followed by radical dispersion polymerization in the presence of the crosslinker EDMA monomer. The resulting crosslinked PStBP micrometer‐sized particles retained the unique high affinity of the hydroxy‐bisphosphonate side groups to calcium ions and exhibited good adhesive properties to HAP. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and cationic photopolymerization of electroactive monomers containing functional groups

The synthesis and cationic photopolymerization of different cationically polymerizable monomers containing electroactive groups are reviewed with 98 references. The preparation of various compounds containing electron‐donor or electron‐acceptor moieties and photopolymerizable functional groups is described. After a short discussion of basic principles of cationic polymerization, photoinduced cationic polymerizations of various cationically polymerizable monomers containing both electron‐donor or electron‐acceptor chromophores and the functional groups such as epoxy, vinyl, thiiranyl, oxetanyl and others are reviewed. Copyright © 2005 John Wiley & Sons, Ltd.     

Preparation of Bowl-Like Polymer Particles via Multi-Step Emulsion Polymerization and Alkali Post-Treatment

Summary : Monodisperse P(BA-MMA-MAA-EGDMA)/P(St-MAA-DVB) core/shell latex particles were first synthesized by a four-step emulsion polymerization, and a new kind of latex particles with “bowl-like” morphology were obtained by post-treating the resultant core/shell particles under alkali condition. Results indicated that the feeding rates of the monomer mixture and initiator aqueous solution were the key parameters to obtain monodisperse core/shell latex particles in the emulsion polymerization process, and the latex particles with “bowl-like” morphology could be generated only when the treatment temperature was equal or higher than 70 °C.     

PMMA/P(AN-MMA)纳米复合粒子的制备与形貌表征

采用种子乳液聚合的方法制备PMMA／P(AN-MMA)纳米复合粒子,在第二阶段聚合过程中分别采用水溶性引发剂、油溶性引发剂以及氧化还原引发体系,通过透射电子显微镜(TEM)来观察复合乳胶粒子的形态结构,得到的PMMA／P(AN-MMA)纳米复合粒子为半球形结构,与热力学理论预测结果一致。     

Thermodynamic and Transport Properties of Two-temperature Oxygen Plasmas

Thermodynamic and transport properties of two-temperature oxygen plasmas are presented. Variation of species densities, mass densities, specific heat, enthalpy, viscosity, thermal conductivity, collision frequency and electrical conductivity as a function of temperature, pressure and different degree of temperature non-equilibrium are computed. Reactional, electronic and heavy particle components of the total thermal conductivity are discussed. To meet practical needs of fluid-dynamic simulations, temperatures included in the computation range from 300 K to 45,000 K, the ratio of electron temperature (T _e) to the heavy particle temperature (T _h) ranges from 1 to 30 and the pressure ranges from 0.1 to 7 atmospheres. Results obtained for thermodynamic equilibrium (T _e = T _h) under atmospheric pressure are compared with published results obtained for similar conditions. Observed overall agreement is reasonable. Slight deviations in some properties may be attributed to the values used for collision integral data and for the two temperature formulations used. An approach for computing properties under chemical non-equilibrium and associated deviations from two-temperature results under similar conditions are discussed.     

功能接枝微粒PVI—SiO2的制备及其吸附特性初探

在偶联剂7-（甲基丙烯酰氧）丙基三甲氧基硅烷的媒介作用下,在溶液聚合体系中,采用“接出”法将功能单体1一乙烯基咪唑（VI）接枝聚合于微米级硅胶微粒表面,制得了功能接枝微粒PVI—SiO2。采用红外光谱（FT—IR）、扫描电镜（SEM）及热失重分析（TGA）等方法对PVI—SiO2进行了表征;测定了接枝微粒的Zeta电位;考察研究了主要因素对接枝聚合的影响;初步探索了其对铬酸根负离子及重金属离子的吸附特性。研究结果表明：本接枝聚合体系亦呈现在固体微粒表面接枝聚合的一般规律,即已接枝到硅胶微粒表面的聚合物层,会对后续的接枝聚合产生阻隔作用;温度及引发剂用量等因素显著影响接枝度,在适宜条件下每100gPVI—SiO2接枝PVI21．63g。在较大的pH范围内,接枝微粒的Zeta电位为较大的正值,在静电相互作用下,接枝微粒对铬酸根离子会产生很强的吸附作用,吸附量可高达120mg／g;凭借配位鳌合作用,接枝微粒对重金属离子具有强的吸附能力。     

核交联型双亲聚合物胶体粒子的制备及其乳化性能

以三硫代碳酸酯为链转移剂,合成了端羧基聚(丙烯酸-r-苯乙烯)(P(AA-r-St))大分子链转移剂;将其用于二乙烯基苯的可逆加成-断裂链转移自由基(RAFT)聚合,一步制备了以交联聚二乙烯基苯为内核、P(AA-r-St)为核外大分子链的双亲聚合物胶体粒子。通过红外光谱、核磁共振氢谱和凝胶渗透色谱确定了大分子链转移剂的化学结构;采用纳米粒度仪、扫描电子显微镜和水接触角测试对胶体粒子的尺寸、形貌及亲-疏水性进行了表征。研究了核外大分子链的化学组成、水相pH、油-水体积比以及油相类型对胶体粒子乳化性能的影响,并通过油相固化的方式考察了胶体粒子在油-水界面的形貌。结果表明:改变核外大分子链的化学组成可有效调控胶体粒子的尺寸、亲-疏水性及乳化性能;当核外大分子链中疏水基元St的物质的量分数为11%时,胶体粒子能够在较宽的pH范围(3~11)稳定水包油型乳液,最大油相体积分数达66.7%;胶体粒子吸附于油-水界面上,有效阻止了乳液滴的聚并;此外,胶体粒子可长效稳定多种油-水体系,作为颗粒乳化剂具有良好的普适性。     

高分子多孔微球产品的制备及其在类病毒颗粒分离纯化中的应用

高分子多孔微球在医药领域的分离纯化中应用广泛,是重要的化工产品。高分子多孔微球的形成是一个复杂的过程,利用聚合物与有机溶剂致孔剂的相分离,可得到小于100 nm孔径的多孔微球;而水和疏水性聚合物之间相分离程度远大于有机溶剂与聚合物间的相分离程度,因此可获得大于100 nm孔径的多孔微球。针对不同应用领域选择不同的方法,设计并制备出合理的微球结构,对多孔微球的实际应用十分关键。本综述介绍了纳孔、介孔、大孔微球产品的制备方法悬浮聚合和种子聚合法,重点介绍本课题组制备超大孔微球的方法--反胶团溶胀法和W/O/W复乳法,上述两种方法解决了常规方法难以制备大孔径微球产品的问题,拓展了多孔微球在类病毒颗粒等大尺寸蛋白分离纯化领域的应用。在此基础上,以HB-VLPs为模型对比了不同孔径微球对类病毒颗粒吸附量、回收率、结构、以及纯化效果的差异,揭示超大孔微球产品在类病毒颗粒分离纯化中的优势。