Monodispersed polymer particles with tunable surface structures: Droplet microfluidic-assisted fabrication and biomedical applications

Polymer particles are key materials in various biomedical applications, including drug delivery, cellular immunity, cell capture, biochip, etc. Droplets produced by microfluidics have been widely applied as templates for the fabrication of polymer particles with controllable sizes and narrow size distributions. Compared to smooth polymer particles, those with surface microstructures (e.g., tentacles, bubbles, wrinkles and pits) are more attractive due to their increased surface area and biomimetic structural characteristics. In this review, we summarized representative methods for the preparation of monodispersed polymer particles with various surface microstructures based on droplet microfluidics, as well as their typical bioapplications in drug delivery, cellular immunity and cell capture. Finally, the current challenges and further development in this research area are discussed.     

Separation of cationic polymer particles and characterization of avidin-immobilized particles by capillary electrophoresis

Cationic polymer microparticles have received much attention especially in the field of biotechnology, such that their analysis and separation have become important. So far, the separation of cationic polymer particles with different size using CE has not been achieved and the cationic particles migrated as if they are negatively charged, probably due to electrostatic interaction between capillary wall and cationic polymer particles. In this paper, the separation of cationic polymer microparticles by CE was investigated in detail. The separation of cationic particles with different size was achieved in CE by taking into account the interaction between sample particles and the inner surface of capillaries. By employing a poly(vinyl alcohol)-coated capillary, a better size separation of amine-modified latex particles was obtained compared to a Polybrene-coated capillary. It was elucidated that the composition, concentration, and pH of the background solution were also important factors in the separation of colloidal particles to avoid the surface adsorption and the characteristic aggregation of polymer particles. Furthermore, the CE analysis was applied to the characterization of cationic protein-immobilized particles.     

SiO2/聚合物核壳型杂化粒子及其空心结构的制备

SiO2/聚合物核壳型杂化粒子及其空心结构以其独特的形貌在药物控制释放、催化剂载体、生物医药等领域应用前景广阔,引起了人们的广泛关注。本文着重从乳液聚合法、仿生矿化法等制备方法角度阐述了SiO2/聚合物核壳型杂化粒子及其空心结构的研究进展。乳液聚合制备SiO2/聚合物核壳型杂化粒子简单易行,一般需要预先合成SiO2纳米粒子,其合成过程通常需要一些非理想的条件,如高温高压、极端pH、昂贵或有毒的有机试剂等,而且预先合成的SiO2粒子无法与聚合物实现100%匹配,即总有纯的聚合物粒子存在。相比之下,原位仿生矿化法制备SiO2杂化粒子不仅在环境条件下可进行,而且能够精确控制其纳米尺度的形态及分级有序结构。目前对材料科学家来讲,要使人工合成SiO2/聚合物杂化粒子实现像自然生物硅那样优异的性能,仍然是很大的挑战。     

超细金属铁颗粒的高分子修饰及其悬浮液的磁流变性能

报道以γ射线辐照方法合成出具有良好分散性的高分子复合金属铁粒子.分别选择十二烷基硫酸钠、溴化十六烷基三甲基铵、Tween-80、TritonX-200和OP-10等表面活性剂和有机单体、无机铁颗粒一起制备乳状液,通过对这种含有超细金属铁颗粒乳状液稳定性的比较,以寻求合适的乳化剂.并对以TritonX-200为乳化剂时合成出的高聚物复合铁颗粒进行了XRD、TEM和IP表征.还将实验中所获得的高聚物复合铁粒子与粒径相同的未经修饰的纯铁粒子分别制成了悬浮液,对两者的悬浮性能进行了比较,同时,也将高聚物复合铁粒子制成的悬浮液与Fe3O4-PMMA复合粒子悬浮液两者的屈服应力随磁场变化情况进行比较研究.     

Inorganic–Polymer Composite Membranes for Proton Exchange Membrane Fuel Cells

Composite membranes consisting primarily of a polymer and an inorganic proton conducting particle or a proton conducting polymer containing inorganic particles for use as proton exchange membranes in low and intermediate temperature fuel cells are reviewed. The chemistry of major inorganic additives that have been used is described in terms of their structure and intrinsic ability to conduct protons. Composites are classified in terms of four main classes: inorganic proton conductors suspended in inert polymers; inorganic particles added to extend polymeric ionomers; inorganic proton conductors blended with polymeric ionomers; and polymer acid complexes between basic polymers and acidic inorganic particles.     

Electrochemistry of conductive polymers 39. Contacts between conducting polymers and noble metal nanoparticles studied by current-sensing atomic force microscopy

Electrical properties of contacts formed between conducting polymers and noble metal nanoparticles have been examined using current-sensing atomic force microscopy (CS-AFM). Contacts formed between electrochemically prepared pi-conjugated polymer films such as polypyrrole (PPy), poly(3-methylthiophene) (P3MeT), as well as poly(3,4-ethylenedioxythiophene) (PEDOT) and noble metal nanoparticles including platinum (Pt), gold (Au), and silver (Ag) have been examined. The Pt nanoparticles were electrochemically deposited on a pre-coated PPy film surface by reducing a platinum precursor (PtCl62-) at a constant potential. Both current and scanning electron microscopic images of the film showed the presence of Pt islands. The Au and Ag nanoparticles were dispersed on the P3MeT and PEDOT film surfaces simply by dipping the polymer films into colloid solutions containing Au or Ag particles for specified periods (5 to approximately 10 min). The deposition of Au or Ag particles resulted from either their physical adsorption or chemical bonding between particles and the polymer surface depending on the polymer. When compared with PPy, P3MeT and PEDOT showed a stronger binding to Au or Ag nanoparticles when dipped in their colloidal solutions for the same period. This indicates that Au and Ag particles are predominantly linked with the sulfur atoms via chemical bonding. Of the two, PEDOT was more conductive at the sites where the particles are connected to the polymer. It appears that PEDOT has better aligned sulfur atoms on the surface and is strongly bonded to Au and Ag nanoparticles due to their strong affinity to gold and silver. The current-voltage curves obtained at the metal islands demonstrate that the contacts between these metal islands and polymers are ohmic.     

Dynamic light scattering studies of poly(ethylene oxide) adsorbed on Laponite: layer conformation and its effect on particle stability

Dynamic light scattering has been used to determine the hydrodynamic thickness of poly(ethylene oxide) (PEO) adsorbed on synthetic anisotropic clay particles (Laponite) as a function of molecular weight. The layer thicknesses, and their increase with molecular weight, indicate that the conformation of the adsorbed layer is very compact and is much smaller than those normally observed for polymer adsorption on flat interfaces. The aggregation kinetics of the polymer coated particles in 5 mM NaCl was analyzed in a quantitative manner, revealing that the potential barrier to aggregation is strongly enhanced when polymer is present.     

Conducting polymer nanostructures and their application in biosensors

Nowadays, functionalized conducting polymer nanomaterials have been received great attention in nanoscience and nanotechnology because of their large surface area. This article reviews various methods for synthesis of conducting polymer nanostructures and their applications in sensing materials, focusing on hard-template, soft-template and other methods and the formation mechanism of conducting polymer nanostructures by these methods. Conducting polymer nanostructures, such as nanotubes, nanowires, and nanoparticles, as sensing platforms for various applications are also summarized.     

Polymerization of styrene in the presence of monoesters of aromatic dicarboxylic acids as surfactants

The colloidal properties of monoesters of aromatic dicarboxylic acids and the heterophase polymerization of styrene in their presence have been studied. It has been shown that particles are formed from micro-droplets of the monomer. A high stability of polymer suspensions during the synthesis has been found to be provided by a strong interfacial adsorption layer formed on the surface of particles from the polymer being synthesized and a surfactant.     

Electroadhesive properties of polymer particles in contact with the photoconductor surface

The electroadhesive properties of polymer particles 5 to 30 μm in diameter have been assessed by the values of their individual charges after tearing off, and by the force of their adhesion to a solid surface. It has been established that the electroadhesion properties of polymer particles are largely determined by the donor-acceptor interaction between the main functional groups of polymers and the solid surface.

The electroadhesive properties of particles in contact with the surface of a photoconductor have been found to be affected by exposure to light. The spectral dependence of the adhesion force of particles and the variation in the distribution of the torn-off particles with regard to a charge sign under the effect of exposure to light are related to a variation in the density of the double electric layer at their interface with the solid surface.

The results obtained are interpreted on the basis of notions on the preponderant role of the forces of electrostatic nature, which are attributable to the effect of the double electric layer at the interface, in the adhesion interaction of the particles with the solid surface.     

Effects of Inorganic Nano-Additives on Properties and Performance of Polymeric Membranes in Water Treatment

Separation using selective polymeric membranes has been well-established as an energy-efficient and cost-effective technology in water treatment and many other applications involving aqueous solutions. However, limited chemical, thermal, and mechanical resistances besides their tendency to fouling and inadequate pure water flux may often restrict their applications. To this end, inorganic materials as additives have been demonstrated to be able to enhance chemical, thermal, and fouling membrane resistances, which demonstrate their great potential for developing novel membranes by using them as additives in polymer matrices. Considering the excellent characteristics of the nanosized particles, this study reviews the effects of inorganic nano-additives on properties and performance of polymer/nanoparticle composite membranes. It has been demonstrated that using nanomaterials in a polymer matrix could enhance the mechanical strength and stiffness, wettability, selectivity, water permeability, and antifouling characteristics of the host polymer.     

Application of particles as pseudo-stationary phases in electrokinetic chromatography

Since the introduction of micelles by Terabe et al. (1984), many different species have been employed as carriers for electrokinetic chromatography. As it is not possible to separate uncharged solutes or ions with equal mobility in capillary electrophoresis, these phases are added to introduce or improve selectivity.

This review surveys the application of particles as pseudo-stationary phases. Up to now only very few applications exist based either on polymer particles for the separation of catechols and primary amines or silica-based material. With these particles separations are shown for phenols, polycyclic aromatic hydrocarbons and naphthalene derivatives. The characteristic properties of particles as pseudo-stationary phases and their benefits as well as their limitations are discussed.     

Effect of associating polymer on the viscosity behavior of suspensions consisting of particles with different surface properties

Associating polymers which consist of water-soluble long-chain molecules containing a small fraction of hydrophobic groups (hydrophobes) behave as flocculants in aqueous suspensions. The effects of associating polymers on the rheological behavior are studied for single suspensions of particles with hydrophilic and hydrophobic surfaces, and their mixtures. For particles with hydrophilic surfaces, the suspensions are highly flocculated by a bridging mechanism, because the water-soluble chains adsorb onto hydrophilic surfaces. On the other hand, the particles with hydrophobic surfaces cannot be dispersed in water without polymer and the additions of a small amount of polymer are required for preparation of homogeneous suspensions. The associating polymer acts as a dispersant at low concentrations. However, further additions of polymer lead to a drastic increase in viscosity. Since the hydrophobes on one end of molecules adsorb onto hydrophobic surfaces and other hydrophobes tending from the particles can form micelles, the particles are connected by linkage of interchain associations. By mixing two suspensions of particles with hydrophilic and hydrophobic surfaces, the viscosity is substantially reduced and the flow becomes nearly Newtonian. The associating polymer in complex suspensions acts as a binder between the hydrophilic and hydrophobic surfaces. The hetero-flocculation which leads to the formation of composite particles may be responsible for the viscosity reduction of complex suspensions.     

A study of the interaction between polyelectrolyte-coated nanostructured CaCO<Subscript>3</Subscript> particles and a stearic acid monolayer spread at the water/air interface

The influence of nanostructured CaCO₃ particles, both uncoated and coated with a polyelectrolyte (poly(diallyldimethylammonium chloride), polyethyleneimine, fluorescein-5-isothiocyanate-labeled poly(allylamine hydrochloride), or sodium polystyrene sulfonate), on a stearic acid monolayer spread on the surface of an aqueous subphase has been studied. The interaction of the particles present in the subphase with the monolayer as depending on the presence and composition of a polymer coating has been estimated with the help of compression isotherms and the Brewster angle microscopy. The monolayers were transferred from the aqueous subphase onto a solid substrate and studied by scanning electron microscopy. Strong interaction has been revealed between the calcium carbonate particles and the stearic acid monolayer. It has been shown that the transfer of the monolayer from the aqueous suspension surface onto the solid substrate may be accompanied by the detachment of the polymer coating from the surface of CaCO₃ particles or their transfer together with the monolayer.     

Composite polymer particles prepared with different amounts of acrylic acid and their usefulness as carriers for biomolecules

Modification of surface properties of polymer particles suitable for biomedical application has been done by incorporating acrylic acid (AA) as a hydrophilic component. First, submicron-sized poly(methyl methacrylate) seed particles were prepared by soap-free emulsion polymerization. Then, seeded emulsion copolymerizations were carried out with varying proportions of AA and methyl methacrylate (MMA). MMA was used as a comonomer to prevent the dissolution of AA from the polymer particles. The adsorption behaviors of different biomolecules indicate that the surface of the composite polymer particles is sufficiently hydrophilic, particularly at higher AA content. Specific activities of adsorbed trypsin on the composite polymer particles were also comparatively high compared to free trypsin, which suggests that the adsorbed trypsin undergoes only slight conformational change owing to the interaction with the surface of particles.     

Deposition studies of carbon particles on stainless steel surfaces from hydrocarbon media

The adsorption isotherms for carbon particles of about 200 nm size, in the presence of various combinations of a terminally functionalised (amine) polyisobutylene polymer and alkylpropoxylate/alkylbutoxylate surfactant molecules, on 7 μm diameter stainless steel beads from isooctane solutions have been obtained. The deposition of carbon particles on stainless steel plates was achieved using a flow-cell and analysed using scanning electron microscopy. The flow-cell was also used to study the “cleaning” properties of various polymer/surfactant solutions, in their ability to remove deposited particles. It was found that the polymer molecules were much more effective dispersants and stabilisers for the carbon particles, but the surfactant molecules were much better at effecting anti-deposition and subsequent removal of deposited carbon particles, and provide carried adsorbed polymer chains.     

The Correlation Functions of a Suspension of Large Particles in Amorphous Polybutadiene: A Molecular Dynamics Simulation Study

The correlation functions of a suspension of Lennard-Jones large particles in a model 1,4-cis-polybutadiene solvent have been investigated by molecular dynamics simulations. We present the effects of temperature, the degree of polymerization, and the solvent/large particle density on the effective interactions between the large particles and the solvent. It is found that as the temperature increases, the structure between solvent-solvent, solvent-large particle, and large-large particle decreases. Additionally, as the bulk density or the chain length is increased, the attractive part of the large-large interaction becomes weaker and small. We believe that in part, this is due to the polymer having collapsed onto itself and entangling the large particles and lessening their interaction until they are actually in contact. Increasing the length of the polymer also entangles the large particles. However, we believe that this may be a general feature that is a characteristic of a polymer solvent containing macroscopically large colloidal particles even though entanglement should be of less significance. Copyright 2000 Academic Press.     

Emission-Color Control in Polymer Films by Memorized Fluorescence Solvatochromism in a New Class of Totally Organic Fluorescent Nanogel Particles

In this work, a new class of totally organic fluorescent nanogel particles and their exceptionally specific behaviors based on their unique structures are introduced, which draws a sharp line from conventional fluorophore-doped and fluorophore-branched-type particles. The nanogel particles, the diameter of which could be controlled by adjusting reaction conditions, such as the solvent system, were spontaneously fabricated with a spherical shape by direct polymerization of non-heterocyclic aromatic compounds, such as 2,6-dihydroxyanthracene, 2,6-dihydroxynaphthalene, and 9,9-bis(4-hydroxyphenyl)fluorene with triazinane as the cross-linker. A fluorophoric moiety formed from a polymer main chain was realized in the particle, and consequently, the resultant content of the fluorophoric moiety was around 70–80 wt % per particle. The uniqueness and versatility of the particles can be emphasized by their good compatibility with various solvents due to their amphiphilic and ampholytic swelling properties, but also by their remarkable fluorescent solvatochromism in the dispersion state. Furthermore, these behaviors were preserved even in their polymer composite system. This study also demonstrates that various fluorescent polymer films can be fabricated with emission color control due to memorization of the solvatochromism phenomenon of the dispersed fluorescent nanoparticles.     

Dynamic modeling of the morphology of multiphase waterborne polymer particles

Multiphase waterborne polymer particles provide advantages in more demanding applications, and their performance depends on particle morphology. Currently, no dynamic model for the prediction of the development of the morphology of multiphase latex particles is available. In this work, a model was developed for the prediction of the dynamic development of the morphology of multiphase waterborne systems, such as polymer–polymer and polymer–polymer–inorganic hybrids.     

聚合物中空微球的合成策略（英文）

在过去的20年中,聚合物中空微球由于其独特的结构和优异的性质受到了广泛的关注.它们表现出低密度、高比表面积和高负载力的特性,在催化、药物递送及能量存储等领域中展现出巨大的应用前景.本文综合评述了聚合物中空微球的合成策略,主要包括模板法、乳液聚合法、自组装与及微流控等,并详细阐述和讨论了这些合成策略的原理、典型过程以及优缺点.同时,还指出了现有合成策略面临的挑战以及聚合物中空微球存在的不足,并对聚合物中空微球的制备和应用前景进行了展望.