Showing papers in "Advances in Polymer Science in 2010"

Organic/Inorganic Composite Latexes: The Marriage of Emulsion Polymerization and Inorganic Chemistry

Abstract: This review article describes recent advances in the synthesis and properties of waterborne organic/inorganic colloids elaborated through conventional emulsion polymerization, a well-established technology These materials can be defined as aqueous suspensions of composite latex particles made up of organic and inorganic domains organized into well-defined core–shell, multinuclear, raspberry-like, multipod-like, or armored morphologies Particular emphasis is placed on the synthetic strategies for fabrication of these colloidal materials Two main approaches are described: the polymerization of organic monomers in the presence of preformed inorganic particles, and the reverse approach by which inorganic materials are synthesized in the presence of preformed polymer latexes The list of examples provided in this review is by no means exhaustive but rather intends to give an overview of synthetic methods for selected inorganic compounds (eg, silica, iron oxide, pigments, clays, quantum dots, and metals), and briefly reports on potential applications of the resulting materials

Miniemulsion Polymerization as a Means to Encapsulate Organic and Inorganic Materials

Abstract: The miniemulsion technique greatly enhances the possibilities for the preparation of hybrid nanomaterials by encapsulating molecular compounds, liquids, or solid material. Using this technique, a wide variety of novel functional nanocomposites can be generated that are not accessible with other techniques. After briefly introducing miniemulsions and the miniemulsion polymerization techniques for the preparation of polymeric nanoparticles, this review focuses on the preparation of functional nanostructures by encapsulation of organic or inorganic material in polymeric matrices. The examples presented highlight the possibility to either protect the encapsulated material (e.g., dyes, drugs, magnetite, or DNA) and create completely new properties that emerge in a synergistic manner from the components of the nanocomposites, or to perform reactions in polymer-enclosed vessels of submicrometer size.

Encapsulation by Miniemulsion Polymerization

Abstract: The miniemulsion technique offers the possibility for the encapsulation of different materials, ranging from liquid to solid, from organic to inorganic, and from molecularly dissolved to aggregated species into polymeric nanoparticles or nanocapsules. Using this technique, a wide variety of novel functional nanomaterials can be generated. This review focuses on the preparation of functional nanostructures by encapsulating organic or inorganic material in polymeric nanoparticles. The examples demonstrate the possibilities to protect the encapsulated material as dyes, pigments, fragrances, photo-initiators, drugs, magnetite, or even DNA, use them as marker systems (dyes, magnetite), or create nanoparticles with completely new properties.

Enzyme-Encapsulated Layer-by-Layer Assemblies: Current Status and Challenges Toward Ultimate Nanodevices

Abstract: Alternate layer-by-layer (LbL) adsorption has received much attention as an emerging methodology. Biocompatibility is the most prominent advantage of the LbL assembly process because the technique employs mild conditions for film con- struction. Most enzymes, especially water-soluble ones, have charged sites at their surfaces so that electrostatic LbL adsorption is suitable for construction of various protein organizations. In this review chapter, we summarize recent developments on enzyme-encapsulated LbL devices and their related functions where "encapsulated" does not always entail entrapment within spherical structures but generally includes immobilization of enzymes within the LbL structures. Recent examples, with vari- ous functions such as reactor sensors and medical applications, are described within a classification of structural types, i.e., thin films and spherical capsules. In addi- tion to conventional applications, advanced systems including integration of LbL structures into advanced devices such as microchannels, field effect transistors, and flow injection amperometric sensors are introduced as well as recent developments in hybridization of LbL assemblies with functional nanomaterials such as carbon nanotube, dendrimers, nanoparticles, lipid assemblies, and mesoporous materials, all of which can enhance bio-related functions of LbL assemblies.

Polymersomes: A Synthetic Biological Approach to Encapsulation and Delivery

Abstract: Compartmentalization, i.e. the ability to create controlled volumes and separate molecules one from another is possibly the most important requisite for complex manipulations. Indeed, compartmentalization has been the first step to isolate the building blocks of life and ensure the dynamic nature that today makes the complexity of any living system. For decades scientists have tried using many synthetic approaches to imitate such ability and one the most successful comes from mimicking the biological component responsible for the compartmentalization: the phospholipid. We are now able to synthesize macromolecular analogues of the phospholipid using advanced co-polymerization techniques. Copolymers that comprise hydrophilic and hydrophobic components (i.e. amphiphilic) can be designed to self assemble into membrane enclosed structures. The simplest of those is represented by a sac resulting from the enclosure of a membrane into a sphere: the vesicle. Vesicles made of amphiphilic copolymers are commonly known as polymersomes and are now one of the most important nanotechnological tool for many applications spanning from drug delivery, gene therapy, medical imaging, electronics and nanoreactors. Herein we review the molecular properties, the fabrication processes and the most important applications of polymersomes.

Rubber–Clay Nanocomposites: Some Recent Results

Abstract: In order to produce high-performance elastomeric materials, the incorporation of different types of nanoparticles such as layered silicates, layered double hydroxides (LDHs), carbon nanotubes, nanosilica, etc. into the elastomer matrix is now a growing area of rubber research. However, the reflection of the “nanoeffect” on the properties and performance can be realized only through a uniform and homogeneous dispersion of filler particles in the rubber matrix. Generally, the properties and the performance of a reinforced elastomeric composite predominantly depend on the crosslinking chemistry of the rubbers, the nature of the fillers, the physical and chemical interaction of the fillers with the rubber matrix and, especially, on the degree of filler dispersion in the rubber matrix. This article is therefore aimed exclusively at addressing the prevailing problems related to the filler dispersion, intercalation, and exfoliation of layered clays in various rubber matrices and compositions to produce advanced high-performance elastomeric nanocomposites. The effect of two chemically distinct layered nanofillers, namely montmorillonite and LDH, on the curing behavior, mechanical, thermo-mechanical, and dielectric properties, etc. are systematically discussed with respect to various elastomeric systems. Different attempts, such as melt interaction, master batch dilution techniques, and further chemical modification of the organoclay, have been taken into consideration and a major portion of this paper will be dedicated to these works.

Shape-Memory Polymer Composites

Abstract: The development of shape-memory polymer composites (SMPCs) enables high recovery stress levels as well as novel functions such as electrical conductivity, magnetism, and biofunctionality. In this review chapter the substantial enhancement in mechanical properties of shape-memory polymers (SMPs) by incorporating small amounts of stiff fillers will be highlighted exemplarily for clay and polyhedral oligomeric silsesquioxanes (POSS). Three different functions resulting from adding functional fillers to SMP-matrices will be introduced and discussed: magnetic SMPCs with different types of magnetic nanoparticles, conductive SMPCs based on carbon nanotubes (CNTs), carbon black (CB), short carbon fiber (SCF), and biofunctional SMPCs containing hydroxyapatite (HA). Indirect induction of the shape-memory effect (SME) was realized for magnetic and conductive SMPCs either by exposure to an alternating magnetic field or by application of electrical current. Major challenges in design and fundamental understanding of polymer composites are the complexity of the composite structure, and the relationship between structural parameters and properties/functions, which is essential for tailoring SMPCs for specific applications. Therefore the novel functions and enhanced properties of SMPCs will be described considering the micro-/nanostructural parameters, such as dimension, shape, distribution, volume fraction, and alignment of fillers as well as interfacial interaction between the polymer matrix and dispersed fillers. Finally, an outlook is given describing the future challenges of this exciting research field as well as potential applications including automotive, aerospace, sensors, and biomedical applications.

Preparation of Hybrid Latex Particles and Core–Shell Particles Through the Use of Controlled Radical Polymerization Techniques in Aqueous Media

Abstract: The synthesis of hybrid and core–shell nanoparticles using controlled/ living radical polymerization in aqueous dispersed systems is reviewed. The processes involve emulsion, miniemulsion, and dispersion polymerizations as well as grafting techniques, with the aim of producing submicrometric latex particles with well-defined morphologies that might not be accessible via classical radical polymerization. Those morphologies include organic/inorganic hybrids, nanostructured particles, (nano)capsules, and particles with a hydrophobic core and hydrophilic shell.

Microgels by Precipitation Polymerization: Synthesis, Characterization, and Functionalization

Abstract: This chapter reviews recent work on the synthesis of aqueous microgel particles by precipitation polymerization. Precipitation polymerization allows flexible control over important physicochemical properties of aqueous microgels, such as size distribution, surface charge, chemical composition, and microstructure. The microgel systems discussed in this review are mainly based on poly(N-isopropyl acrylamide) and poly(N-vinylcaprolactam) due to their ability to react to external stimuli such as the pH or temperature of the surrounding medium. We discuss synthetic routes to obtain microgels based on homo- or copolymers as well as colloids with complex core-shell morphology. The functionalization of microgels is of crucial importance from the application point of view. Different routes for incorporation of functional groups, synthetic polymers, proteins, or nanoparticles in microgel structures are discussed.

Microgels as Nanoreactors: Applications in Catalysis

Abstract: We review recent work on the use of "smart" microgel particles as "nanoreactors" for the immobilization of metal nanoparticles as well as enzymes. A general feature of the microgel systems under consideration is their ability to react to external stimuli such as the pH or temperature of the system. Special emphasis is given to our recent research work on thermosensitive core-shell microgel particles composed of a polystyrene core and a crosslinked poly(N-isopropylacrylamide) shell. Work done on these core-shell systems is compared to developments in the investigation of similar systems. Recently, it has been shown that these coreshell microgels can be used as "nanoreactors" for the immobilization of metal nanoparticles. The metal nanocomposite particles exhibit a "smart" catalytic behavior inasmuch as the catalytic activity of nanoparticles can be modulated through the volume transition that takes place within the thermosensitive shell of the carrier system. Moreover, microgel particles can work as efficient carrier systems for the immobilization of enzymes. The dependence of the enzymatic activity on temperature can also be manipulated by the temperature-dependent swelling behavior of the microgel. Thus, the microgel particles present an excellent "active" carrier system for applications in catalysis.

Nanopattern Evolution in Block Copolymer Films: Experiment, Simulations and Challenges

Abstract: The present contribution reviews novel insights into block copolymer phase behavior and nanostructure formation in confined geometries. We focus on state-of-the-art experimental and theoretical progress in this area, with an emphasis on characterization methods and techniques that provide a quantitative framework for fundamental analysis. We discuss and compare basic system parameters that are readily controlled in simulations and in experiments, and present comparative stud- ies of increasing degree of complexity concerning the phase behavior and ordering dynamics of cylinder- and lamella-forming block copolymers in thin films.

Poly(substituted Methylene) Synthesis: Construction of C―C Main Chain from One Carbon Unit

Abstract: This review describes recent progress in the preparation of C―C main chain polymers, where the main chain is constructed from one carbon unit. The first example for this strategy is polymerization of diazoalkanes and aryldiazomethanes, which were extensively explored in the period 1950―1970, despite the high explosiveness of the monomers. The metal surface-catalyzed polymerization of diazoalkanes has recently attracted much attention, as an efficient method for coating the surface with nanometer-scale polymethylene thin films, which can be regarded as a useful substitute for polyethylene films. Diazocarbonyl compounds such as diazoacetates, diazoketones, and diazoacetamides with a variety of substituents have been polymerized by Pd-complexes to give poly(substituted methylene)s with polar functional groups. Rh(diene) complexes polymerize ethyl diazoacetate in a stereospecific manner, giving high molecular weight polymers (M n up to 270,000). Organoborane-initiated living polymerization of sulfoxonium methylides is remarkably effective as a method for preparing polymethylenes with a controlled chain length and a well-defined polymer architecture. Some polymerizations related to the above examples are also described.

Recent Advances in the Improvement of Polymer Electret Films

Abstract: Polymer electret materials are electrically charged dielectric polymers capable of quasi-permanently retaining their electric field. However, environmental influences such as temperature and humidity reduce their charge stability and restrict applications. Therefore it is of great importance to provide a broad pool of polymer electret materials and to enhance further the charge storage behavior. In this context we report on concepts, measures, and solutions to improve the electret performance of commodity and high performance thermoplastic polymers, which was carried out at the University of Bayreuth in recent years. It is demonstrated that the commodity polymer polypropylene can be manufactured into excellent electret films when certain trisamide additives are incorporated in very low concentrations. Polypropylene can be employed at temperatures up to its continuous service temperature of 70 ∘C. To achieve higher temperature windows we investigated the commodity blend system of poly(phenylene ether) (PPE) and polystyrene (PS). We demonstrate that especially PPE/PS blend films with a composition of 75/25 exhibit remarkably good charge storage retention during the isothermal surface decay (ITPD) tests at 120 ∘C. In addition, the commercially available high performance thermoplastic polyetherimide (PEI) resin containing special phosphorus(III) additives shows very good electret properties at elevated temperatures. These properties can be further enhanced by physical aging; resulting in a charge retention after 24 h at 120 ∘C as high as 95%. The same beneficial effect of physical aging can be used to advance PPE and PPE/PS blends. Polymer electret materials with such charge storage properties have the potential to be employed in microphones, sensor devices, and electret filters.

LbL Films as Reservoirs for Bioactive Molecules

Abstract: This review presents recent progress in utilizing polymeric films made by the layer-by-layer (LbL) technique (so-called multilayered films) as reservoirs for hosting and releasing bioactive molecules. This relatively new technique is distinguished by its high modularity and structural control at the nanometer level, giving polymeric surface films with tuneable physicochemical properties. A significant increase in research activities regarding the bioapplications of the multilayered films has taken place over the last decade. In this review, we address the bioapplications of LbL films and will focus on the loading and release of the film-embedded bioactive compounds and their bioactivity. Planar and free-standing 3D multilayered polyelectrolyte films (microcapsules) are considered. Special attention is paid to light-stimulated release, interaction of cells with the LbL films, and intracellular light-triggered delivery.

Smart Polymer Surfaces: Concepts and Applications in Biosciences

Abstract: Stimuli-responsive macromolecules (i.e., pH-, thermo-, photo-, chemo-, and bioresponsive polymers) have gained exponential importance in materials science, nanotechnology, and biotechnology during the last two decades. This chapter describes the usefulness of this class of polymer for preparing smart surfaces (e.g., modified planar surfaces, particles surfaces, and surfaces of three-dimensional scaffolds). Some efficient pathways for connecting these macromolecules to inorganic, polymer, or biological substrates are described. In addition, some emerging bioapplications of smart polymer surfaces (e.g., antifouling surfaces, cell engineering, protein chromatography, tissue engineering, biochips, and bioassays) are critically discussed.

Bioactive Polymer/Hydroxyapatite (Nano)composites for Bone Tissue Regeneration

Abstract: Bioactive polymer/hydroxyapatite (nano)composites are currently being intensively investigated as materials for promotion of bone tissue regeneration and reconstruction. The advantages of polymeric biomaterials, compared to metallic or ceramic materials, are the ease of manufacturing components having various and complex shapes, reasonable cost, and their ability to possess a wide range of physical and mechanical properties. Additionally, hydroxyapatite (HAp) is one of the most attractive materials for bone implants because of its composition and biological similarity to natural tissues. It can be obtained in a nanostructured form, which facilitates its fine dispersion in the polymer matrix as well as producing advantageous interactions with bioactive polymer and tissue. This paper reviews recent advances in polymer/(nano)HAp composites and nanocomposites for bone tissue regeneration, with particular emphasis on the material characteristics. Specific topics associated with polymer/HAp composition, molecular orientation and morphology, surface modifications, the interactions between the components, and their biological behaviours are described. Finally, the challenges facing this emerging field of research are outlined.

Making Floryr–Huggins Practical: Thermodynamics of Polymer-Containing Mixtures

Abstract: The theoretical part of this article demonstrates how the original Flory–Huggins theory can be extended to describe the thermodynamic behavior of polymer-containing mixtures quantitatively. This progress is achieved by accounting for two features of macromolecules that the original approach ignores: the effects of chain connectivity in the case of dilute solutions, and the ability of polymer coils to change their spatial extension in response to alterations in their molecular environment. In the general case, this approach leads to composition-dependent interaction parameters, which can for most binary systems be described by means of two physically meaningful parameters; systems involving strongly interacting components, for instance via hydrogen bonds, may require up to four parameters. The general applicability of these equations is illustrated in a comprehensive section dedicated to the modeling of experimental findings. This part encompasses all types of phase equilibria, deals with binary systems (polymer solutions and polymer blends), and includes ternary mixtures; it covers linear and branched homopolymers as well as random and block copolymers. Particular emphasis is placed on the modeling of hitherto incomprehensible experimental observations reported in the literature.

Controlled Wrinkling as a Novel Method for the Fabrication of Patterned Surfaces

Abstract: This contribution reviews recent findings on nonlithographic approaches for topographical structuring of polymeric surfaces and application of the resulting surfaces for creating hierarchical structures. External mechanical fields are used to induce a so-called buckling instability, which causes the formation of wrinkles with well-defined wavelength. We introduce the theoretical foundations of the phenomenon. The universality of the principle and the range of wavelengths between fractions of a micrometer and hundreds of microns that can be achieved are discussed. In the following we focus on the application of these surfaces as templates for the deposition of colloidal particles such as artificial particles (polystyrene beads, gold-nanoparticles or polymeric core-shell particles) and bionanoparticles (tobacco mosaic virus). We demonstrate how patterns can be transferred from the supporting wrinkled surfaces onto a broad variety of flat surfaces like glass or silicon wafers by stamping, where the complex colloidal patterns are accessible for studying their optical, electronic or other physical properties.

Physical Methods for the Preparation of Hybrid Nanocomposite Polymer Latex Particles

Abstract: In this chapter, we will highlight conceptual physical approaches towards the fabrication of nanocomposite polymer latexes in which each individual latex par- ticle contains one or more "hard" nanoparticles, such as clays, silicates, titanates, or other metal(oxides). By "physical approaches" we mean that the "hard" nanoparti- cles are added as pre-existing entities, and are not synthesized in situ as part of the nanocomposite polymer latex fabrication process. We will narrow our discussion to focus on physical methods that rely on the assembly of nanoparticles onto the la- tex particles after the latex particles have been formed, or its reciprocal analogue, the adhesion of polymer onto an inorganic nanoparticle. First, will discuss the phe- nomenon of heterocoagulation and its various driving forces, such as electrostatic interactions, the hydrophobic effect, and secondary molecular interactions. We will then address methods that involve assembly of nanoparticles onto or around the more liquid precursors (i.e., swollen/growing latex particles or monomer droplets). We will focus on the phenomenon of Pickering stabilization. We will then discuss features of particle interaction with soft interfaces, and see how the adhesion of particles onto emulsion droplets can be applied in suspension, miniemulsion, and emulsion polymerization. Finally, we will very briefly mention some interesting methods that make use of interface-driven templating for making well-defined as- sembled clusters and supracolloidal structures.

Hydrolases in Polymer Chemistry: Chemoenzymatic Approaches to Polymeric Materials

Abstract: Lipases show high activity in the polymerization of a range of monomers using ring-opening polymerization and polycondensation. The range of polymer structures from this enzymatic polymerization can be further increased by combination with chemical methods. This paper reviews the developments of the last 5–8 years in chemoenzymatic strategies towards polymeric materials. Special emphasis is on the synthesis of polymer architectures like block and graft copolymers and polymer networks. Moreover, the combination of chemical and enzymatic catalysis for the synthesis of unique chiral polymers is highlighted.

Hybrid latex particles : preparation with (mini)emulsion polymerization

Abstract: Historical Overview of (Mini)emulsion Polymerizations and Preparation of Hybrid Latex Particles, by A.M. van Herk Physical Methods for the Preparation of Hybrid Nanocomposite Polymer Latex Particles, by R. F.A. Teixeira and S. A.F. Bon Organic/Inorganic Composite Latexes: The Marriage of Emulsion Polymerization and Inorganic Chemistry, by Elodie Bourgeat-Lami and Muriel Lansalot Preparation of Hybrid Latex Particles and Core-Shell Particles Through the Use of controlled Radical Polymerization Techniques in Aqueous Media, by Bernadette Charleux, Franck D'Agosto, and Guillaume Delaittre Miniemulsion Polymerization as a Means to Encapsulate Organic and Inorganic Materials, by Clemens K.Weiss and Katharina Landfester Organic-Inorganic Hybrid Magnetic Latex, by Md Mahbubor Rahman and Abdelhamid Elaissari

Historical overview of (mini)emulsion polymerizations and preparation of hybrid latex particles

Abstract: In this introductory chapter, a brief overview of emulsion polymerization and miniemulsion polymerization principles is given in relation to preparation of hybrid latex particles. An account is presented of the early history of preparation of hybrid latex particles with an emphasis on the hybrid lattices containing organic and inorganic material phases. The two approaches for obtaining encapsulated inorganic particles are discussed: the chemical method in which polymerization takes place in the presence of inorganic particles, and the physical method whereby latex particles are deposited on the surface of inorganic particles by heterocoagulation. A new classification scheme for the preparation of hybrid latex particles and corresponding higher-order nanostructures is given in this paper. This classification is partially based on a discussion during the International Polymer Colloids Group meeting in Italy in 2009.

Morphology–Property Relationship in Rubber-Based Nanocomposites: Some Recent Developments

Abstract: Recently, rubber nanocomposites reinforced with a low volume fraction of nanofillers have attracted great interest due to their fascinating properties. Incorporation of nanofillers such as layered and fibrillated silicate clays, carbon nanotubes and nanofibers, calcium carbonate, metal oxides, or silica nanoparticles into elastomers can significantly improve their mechanical, thermal, dynamic mechanical, electrical, aging, barrier, adhesion, and flame retardancy properties. These also significantly alter the rheological behavior of polymers, even at low filler loading. The properties of nanocomposites depend greatly on the structure of the polymer matrices, the nature of nanofillers, and the method by which they are prepared. It has been established that uniform dispersion of nanofillers in rubber matrices is a general prerequisite for achieving desired mechanical, rheological, and physical characteristics. This review paper addresses some recent developments on the morphology–property relationship of rubber-based nanocomposites reinforced with various nanoparticles. New insights into understanding the properties of these nanocomposites and morphology development will be discussed.

Amphiphilic polymers at interfaces

Abstract: Self-assembly phenomena in block copolymer systems are attracting considerable interest from the scientific community and industry alike. Particularly interesting is the behavior of amphiphilic copolymers, which can self-organize into nanoscale-sized objects such as micelles, vesicles, or tubes in solution, and which form well-defined assemblies at interfaces such as air–liquid, air–solid, or liquid–solid. Depending on the polymer chemistry and architecture, various types of organization at interfaces can be expected, and further exploited for applications in nanotechnology, electronics, and biomedical sciences. In this article, we discuss the formation and characterization of Langmuir monolayers from various amphiphilic block copolymers, including chargeable and thus pH-responsive materials. Solid-supported polymer films are reviewed in the context of alteration of surface properties by ultrathin polymer layers and the possibilities for application in tissue engineering, sensors and biomaterials. Finally, we focus on how organic and polymer monolayers influence the growth of inorganic materials. This is a truly biomimetic approach since Nature uses soft interfaces to control the nucleation, growth, and morphology of biominerals such as calcium phosphate, calcium carbonate, and silica.

Interfacial Tension in Binary Polymer Blends and the Effects of Copolymers as Emulsifying Agents

Abstract: The structure and the thermodynamic state of polymeric interfaces are important features in many materials of technological interest This is especially true for multiconstituent systems such as blends of immiscible polymers, where the interface structure can affect greatly their morphology and, thus, their mechanical properties In this article, we first present a review of the experimental and theoretical investigations of the interfacial tension in phase-separated homopolymer blends We emphasize the effects of temperature and molecular weight on the behavior: interfacial tension γ decreases with increasing temperature (for polymer systems exhibiting upper critical solution temperature behavior) with a temperature coefficient of the order of 10–2 dyn/(cm °C), whereas it increases with increasing molecular weight The increase follows a \(\gamma = \gamma _\infty \left( {1 - k_{\operatorname{int} } M_{\text{n}}^{ - z} } \right)\) dependence (with z ≈ 1 for high molecular weights), where γ ∞ is the limiting interfacial tension at infinite molecular weight and M n the number average molecular weight Suitably chosen block or graft copolymers are widely used in blends of immiscible polymers as compatibilizers for controlling the morphology (phase structure) and the interfacial adhesion between the phases The compatabilitizing effect is due to their interfacial activity, ie, to their affinity to selectively segregate to the interface between the phase-separated homopolymers, thus reducing the interfacial tension between the two macrophases The experimental and theoretical works in this area are reviewed herein The effects of concentration, molecular weight, composition, and macromolecular architecture of the copolymeric additives are discussed An issue that can influence the efficient utilization of a copolymeric additive as an emulsifier is the possibility of micelle formation within the homopolymer matrices when the additive is mixed with one of the components These micelles will compete with the interfacial region for copolymer chains A second issue relates to the possible trapping of copolymer chains at the interface, which can lead to stationary states of partial equilibrium The in-situ formation of copolymers by the interfacial reaction of functionalized homopolymers is also discussed

Various Aspects of the Interfacial Self-Assembly of Nanoparticles

Abstract: We describe the interfacial self-assembly of nanoparticles at liquid-liquid interfaces and in block copolymers. At the interface of two immiscible liquids, the particles assemble into disordered but densely packed monolayers. This self- assembly process was investigated ex situ with scanning force microscopy (SFM) and transmission electron microscopy (TEM), and laser scanning confocal mi- croscopy (LCSM) methods. Adsorbed particles can be crosslinked at the interface to fabricate mechanically stable capsules and membranes. In addition, it was shown by pendant drop tensiometry that Janus particles consisting of gold and iron oxide show a significantly higher interfacial activity than homogeneous gold or iron oxide nanoparticles of comparable size and chemical nature. For the self-assembly of nanoparticles in block copolymer mixtures, it was shown theoretically and exper- imentally that these composite materials form hierarchically ordered structures. Therefore, thin films from mixtures of a cylindrical polystyrene-block-poly(2- vinylpyridine), with tri-n-octylphosphine oxide-covered CdSe nanoparticles were prepared and investigated with SFM, TEM, and grazing-incidence small angle x-ray scattering (GISAXS) after thermal annealing.

Gradient and Microfluidic Library Approaches to Polymer Interfaces

Abstract: We present an overview of research conducted at the National Institute of Standards and Technology aimed at developing and applying combinatorial and high-throughput measurement approaches to polymer surfaces, interfaces and thin films. Topics include (1) the generation of continuous gradient techniques for fabricating combinatorial libraries of film thickness, temperature, surface chemistry and polymer blend composition, (2) high-throughput measurement techniques for assessing the mechanical properties and adhesion of surfaces, interfaces and films, and (3) microfluidic approaches to synthesizing and analyzing libraries of interfacially-active polymer species.

Designing Three-Dimensional Materials at the Interface to Biology

Abstract: Modern approaches to the production of 3D materials with bioactive interfaces for tissue engineering, biointegrated materials, and biomimetic materials are reviewed. Recent advances in the understanding of how materials passively interact or actively communicate with biological systems via designed material–biology interfaces demand precise means to fabricate macroscopic nanostructured materials. We review modern materials and technology that are available for the production of bioactive scaffolds having spatial control of mechanical, chemical, and biochemical signals at the interface, as well as tailored pore architecture and surface topology.

Organic-Inorganic Hybrid Magnetic Latex

Abstract: The preparation of magnetic hybrid latex, consisting of inorganic magnetic iron oxide nanoparticles and organic polymer, in dispersed media is reviewed The aim of this chapter is to highlight the recent advances of research into the synthesis of hybrid magnetic latex preparation in dispersed media Although the term "organic-inorganic hybrid composite/latex" covers a wide range of materials, this review will principally focus on the preparation methods, emphasizing emulsion polymerization in the presence of inorganic iron oxide magnetic particles However, some relevant hybrid polymer latexes of other metal oxides and their synthetic methods will be highlighted Furthermore, some applications and properties of magnetic latex, polymerization parameters and the shortcomings of preparation methods will be reviewed

Hydrolases Part I: Enzyme Mechanism, Selectivity and Control in the Synthesis of Well-Defined Polymers

Abstract: Lipases are highly activity in the polymerization of a range of monomers. Both ring-opening polymerization of cyclic esters and polycondensation reactions of AA–BB and AB monomers have been investigated in great detail. This paper reviews the increased understanding in enzymatic strategies for the production of well-defined polymers. Major advantages of enzymatic catalysts are the relatively mild reaction conditions, and the often-observed excellent regio-, chemo-, and enantioselectivity that allow for the direct preparation of functional materials. However, as a result of the monomer activation mechanism, polymers of low polydispersity and low quantitative degree of endgroup functionality are difficult to attain. A wide variety of (co)polymers have been synthesized and explored in a variety of applications using lipase catalysts.