Monodispersed polymer lattice

Emulsion and microemulsion polymerization are the most common ways to produce polymer dispersions and generate latex particles with diameters between 0.05 and 0.5 pm. In contrast to bulk radical polymerization it is possible to obtain high molecular weights at high polymerization rates. A large number of monodisperse polymer lattices with diameters between 20 and 100 nm have been synthesized in oil-in-water emulsions, most importantly for research and industrial processes, from... 

Goodwin, J. W. Ottewill, R. H. Pelton, R., Studies on the preparation and characterization of monodisperse polystyrene lattices V The preparation of cationic latices, Colloid Polymer Sci. 1979,257,61 69... 

In the past few decades, a specific kind of colloidal system based on monodis-perse size has been developed for various industrial applications. A variety of metal oxides and hydroxides and polymer lattices have been produced. Monodisperse systems are obviously preferred since their properties can be easily predicted. On the other hand, polydisperse systems will exhibit varying characteristics, depending on the degree of polydispersity. 

Recently, sub-micron polymer lattices imprinted with theophylline and 17y8-estradiol have been successfully synthesised by precipitation polymerisation in acetonitrile [27]. The particles were both spherical and monodisperse and were obtained in high yield. Binding properties of the beads were shown to be similar to conventionally imprinted materials, although the capacity was higher and equilibration times lower, presumably due to better accessibility of the binding sites in these very small particles. A photograph of the 17 8-estradiol-imprinted latex is shown in Fig. 12.6. 

The occurrence of a secondary phase separation inside dispersed phase particles, associated with the low conversion level of the p-phase when compared to the overall conversion, explains the experimental observation that phase separation is still going on in the system even after gelation or vitrification of the a-phase [26-31]. A similar thermodynamic analysis was performed by Clarke et al. [105], who analyzed the phase behaviour of a linear monodisperse polymer with a branched polydisperse polymer, within the framework of the Flory-Huggins lattice model. The polydispersity of the branched polymer was treated with a power law statistics, cut off at some upper degree of polymerization dependent on conversion and functionality of the starting monomer. Cloud-point and coexistence curves were calculated numerically for various conversions. Spinodal curves were calculated analytically up to the gel point. It was shown that secondary phase separation was not only possible but highly probable, as previously discussed. 

The rigid-lattice expression for AG, the Gibbs free energy of mixing of monodisperse polymers 1 and 2 on N sites, reads [13-19]... 

The polymers should be as well characterized and as monodisperse as possible. Adsorbents should have a well-defined geometry and surface structure (planes or spheres are usually preferred). It is now possible to prepare a wide range of polymer lattices and inorganic particles for use as model surfaces. Any surface heterogeneity should be well characterized e.g., the number density and type of any surface charge should be known. 

Goodwin, J.W., Hearn, J., Ho, C.C., and Ottewill, R.H. (1974) Studies on preparation and characterization of monodisperse polystyrene lattices 3. Preparation without added surface-active agents. Colloid Polym. Sci., 252 (6), 464- 71. 

Owing to the simphcity and versatility of surface-initiated ATRP, the above-mentioned AuNP work may be extended to other particles for their two- or three-dimensionally ordered assemblies with a wide controllabiUty of lattice parameters. In fact, a dispersion of monodisperse SiPs coated with high-density PMMA brushes showed an iridescent color, in organic solvents (e.g., toluene), suggesting the formation of a colloidal crystal [108]. To clarify this phenomenon, the direct observation of the concentrated dispersion of a rhodamine-labeled SiP coated with a high-density polymer brush was carried out by confocal laser scanning microscopy. As shown in Fig. 23, the experiment revealed that the hybrid particles formed a wide range of three-dimensional array with a periodic structure. This will open up a new route to the fabrication of colloidal crystals. 

Semiconductor clusters have traditionally been prepared by the use of colloids, micelles, polymers, crystalline hosts, and glasses. The clusters prepared by these methods have poorly-defined surfaces and a broad size distribution, which is detrimental to the properties of the semiconductor materials. The synthesis of monodisperse clusters with very well-defined surfaces is still a challenge to synthetic chemists. However, some recent approaches used to overcome these problems are (i) synthesis of the clusters within a porous host lattice (such as a zeolite) acting as a template and (ii) controlled fusion of clusters. 

The Flory-Huggins theory begins with a model for the polymer solution that visualizes the solution as a three-dimensional lattice of TV sites of equal volume. Each lattice site is able to accommodate either one solvent molecule or one polymer segment since both of these are assumed to be of equal volume. The polymer chains are assumed to be monodisperse and to consist of n segments each. Thus, if the solution contains TV, solvent molecules and TV2 solute (polymer) molecules, the total number of lattice sites is given by... 

Thus the use amphiphilic macromonomers is another method to achieve the particle formation and their subsequent stabilization. Macromonomers can be pre-reacted to form graft copolymers, which are be introduced into the reaction medium afterwards. Macromonomers can also be copolymerized with classical monomers in situ to form graft copolymers. This is a simple and flexible method for producing monodisperse micron-sized polymer particles. Macromonomers can produce ion-free acrylic lattices with superior stability and film forming properties compared to conventional charge stabilized lattices. These non-con-... 

A variety of methods have been demonstrated for crystallizing monodispersed spherical colloids (such as polymer beads and silica spheres) into long-range ordered lattices. Some of the commonly used ones include sedimentation, self-assembly via repulsive electrostatic interaction, ordering via attractive capillary forces, and crystallization under physical confinement. 

Monodisperse spherical colloids and most of the applications derived from these materials are still in an early stage of technical development. Many issues still need to be addressed before these materials can reach their potential in industrial applications. For example, the diversity of materials must be greatly expanded to include every major class of functional materials. At the moment, only silica and a few organic polymers (e.g., polystyrene and polymethylmethacrylate) can be prepared as truly monodispersed spherical colloids. These materials, unfortunately, do not exhibit any particularly interesting optical, nonlinear optical or electro-optical functionality. In this regard, it is necessary to develop new methods to either dope currently existing spherical colloids with functional components or to directly deal with the synthesis of other functional materials. Second, formation of complex crystal structures other than closely packed lattices has been met with limited success. As a major limitation to the self-assembly procedures described in this chapter, all of them seem to lack the ability to form 3D lattices with arbitrary structures. Recent demonstrations based on optical trapping method may provide a potential solution to this problem, albeit this approach seems to be too slow to be useful in practice.181-184 Third, the density of defects in the crystalline lattices of spherical colloids must be well-characterized and kept below... 

Ungar and Zeng [33] have comprehensively summarized the research on strictly monodisperse materials from their first synthesis in 1985 until 2001. From the earliest studies it became apparent that, due to the monodisper-sity of the materials, the thickness of the lamellar crystals formed is always an integer fraction of the extended chain length (allowing for any chain tilt), such that the polymers always crystallize in the extended chain form or fold exactly in half (once-folded), or in three (twice-folded), etc. This behavior means that, when the alkanes are crystallized at a particular temperature, the entire lamellar population has very closely the same thickness and stability. The use of such an ultra-pure system to study the impact of thickness on lattice parameters removes many of the problems inherent to polymers, whilst maintaining the most important characteristic of chain length. 

Beginning in the 1990s calculations of high-pressure phase equilibria of polydisperse polymer systems were performed. For example, Enders and de Loos calculated cloud-point and spinodal curves in the high-pressure range for methylcyclohexane + poly(ethenylbenzene) and compared their results with experimental data. Enders and de Loos ° used a Gibbs-energy model with pressure dependent parameters and models that include an equation of state, such as the lattice fluid model introduced by Hu et for the monodisperse and... 

Potassium laurate and sodium abietate are often used as emulsifiers that are attached to the surfae of the latex particles. There are also emulsifiers such as maleic acid monoesers, methacrylic acid, and vinyl benzene sulfonic acid that are built into the polymer, thus improving the tensile strength of the final rubber coating [483]. The nature and concentration of the emulsifier is also a means to controlling the particle size distribution of the products. In monodisperse lattices the particle size varies by less than 1% which can be achieved by short polymerization times [484,485]... 

Abstract Using a new lattice polymer simulation method for block copolymers, we have studied a dense polymer system composed of monodisperse linear A-B-C triblock copolymers. We confirm that a tricontinuous structure for linear A-B-C block copolymers observed by Mogi et al. (Macromolecule 25, 5408 (1992) and ibid. 25, 5412 (1992)) could be, indeed, an ordered tricontinuous double-diamond ... 

Monodispersed lattices contain a sizable number of particles with uniform diameter. Their well-defined geometry forms the basis for larger patterns. Thus, instead of defining a number of identical substructures during patterning, only their arrangement is controlled the substructure is efficiently defined by the particle geometry. A serial step is replaced by a parallel, low-cost method, namely, the emulsion synthesis of polymer particles. 

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