Core latex particles

For most biological studies, the ICPs have been prepared in the form of a flat film although some tubular structures have also been prepared. An evolving area of interest is the synthesis of high surface area bioactive colloidal systems [32]. PPy-polystyrene core latex particles with an inner core 600 nm in diameter have been functionalized with N-succinimidyl ester [33,34] and AT-hydroxysuccinimide [35] to introduce protein-binding capacity. Functionalization of these particles exhibited a high degree of... 

In the same year, Fulda and Tieke [75] reported on Langmuir films of monodisperse, 0.5-pm spherical polymer particles with hydrophobic polystyrene cores and hydrophilic shells containing polyacrylic acid or polyacrylamide. Measurement of ir-A curves and scanning electron microscopy (SEM) were used to determine the structure of the monolayers. In subsequent work, Fulda et al. [76] studied a variety of particles with different hydrophilic shells for their ability to form Langmuir films. Fulda and Tieke [77] investigated the influence of subphase conditions (pH, ionic strength) on monolayer formation of cationic and anionic particles as well as the structure of films made from bidisperse mixtures of anionic latex particles. 

TABLE 1 Characteristic Properties of Core-Shell Latex Particles with Polystyrene Core... 

The foregoing examples show that hollow polymer capsules with varying composition and sizes of ca. 2-20 micrometers can be produced, either by templating charged (latex particles and biocrystals) or uncharged (organic microcrystals), and that different core removal procedures can be employed. Nanometer-size polymer capsules have also been produced by employing smaller particle templates [107]. 

The original polymeric latex particles still are widely used for separation and detection. Polymers provide a matrix that can be swollen for embedding other molecules in their core, such as organic dyes or fluorescent molecules. Even nanoparticle quantum dots can be incorporated into larger latex particles to form highly fluorescent composite microparticles. 

Various novel imprinting techniques have also been presented recently. For instance, latex particles surfaces were imprinted with a cholesterol derivative in a core-shell emulsion polymerization. This was performed in a two-step procedure starting with polymerizing DVB over a polystyrene core followed by a second polymerization with a vinyl surfactant and a surfactant/cholesterol-hybrid molecule as monomer and template, respectively. The submicrometer particles did bind cholesterol in a mixture of 2-propanol (60%) and water [134]. Also new is a technique for the orientated immobilization of templates on silica surfaces [ 135]. Molecular imprinting was performed in this case by generating a polymer covering the silica as well as templates. This step was followed by the dissolution of the silica support with hydrofluoric acid. Theophylline selective MIP were obtained. 

Carty, P. White, S. Price, D. Lu, L. (1999) Smoke suppression in plasticised chlorinated poly(vinyl) chloride (CPVC). Polymer Degradation Stability 63 465-468 Caruso, F. Susha, A.S. Giersig, M. Moh-wald, H. (1999) Magnetic core-shell particles Preparation of magnetite multilayers in polymer latex microspheres. Adv. Mater. 11 950-952... 

Figure 3.5 shows aTEM picture of the core/double shell latex particles incorporated into an styrene/acrylonitrile (SAN) copolymer matrix (thin cut through the particle-filled matrix).The particles are very homogeneous in size and can also be used to prepare ar-tifical opals. 

Seeded polymerization using a slight amount of monomer leads to the surface modification without changing particle size. The resulting particles are a kind of core-shell particles or, more exactly, core-skin particles (Fig. 12.2.4C). Seeded polymerization of sugar-units-containing styrene derivative on polystyrene seed particle was carried out to obtain latex particles covered with sugar units (17). A necessary condition for this is that the monomer is more hydrophilic than the seed polymer. If not, the monomer permeates into the seed particle and only a small fraction remains on the... 

Composite core-shell type microspheres were prepared by in situ heterogeneous polymerization on monodispersed seed latex particles suspended in an aqueous magnetite dispersion stabilized with sodium oleate (58). 

Another aspect of seeded polymerization is that a seed may be formed from one monomer composition whereas the added monomer may be of a different composition. This may lead to core-shell latex particles. Such copolymers may have substantially different properties then regular copolymers. 

Other nutshell materials have been synthesised [164]. Hydrophobic latex particles containing a crosslinked poly(VBC) core and a macroporous poly(styrene/DVB) shell were prepared from concentrated o/w emulsions. Similarly, hydrophilic porous particles of crosslinked acrylamide surrounding a linear poly(ethyleneoxide) core were formed from w/o HIPEs. The poly(VBC) cores of the hydrophobic particles were quaternised and used to bind [Co(CO)4] anions, whereas the hydrophilic latexes were employed in the immobilisation of lipase. 

The work represents an application of core-shell light scattering theory to polymer latex suspensions and addresses the separate identification of light scattering by dust, latex particles and low molecular weight solutes. 

The typical results of the wide-angle light-scattering (WALS) analysis on the latex particles that were presumed to be cores are given in Table I where the theoretical model to be fitted was either S = sphere or CS = core-shell, the variance measured the goodness of fit, the modal size parameter is given by aM = 27rr/A, aQ is the log normal breadth parameter, DM is the core diameter in ym, mi the relative refractive index of the core and m2 the relative refractive index of the shell of indicated thickness. 

The morphology of two-stage (styrene//styrene-butadiene) and (styrene-butadiene//styrene) latex particles was found to vary from a core-shell structure to a complete phase separation with various two-phase structures in between, depending on polymerization sequence, polymerization conditions, polymer compatibility, molecular weights, polymer phase ratio, etc. 

The transmission electron microscopy results are consistent with a segregated latex particle consisting of a polystyrene rich core and a soft poly-n-butyl acrylate rich shell. 

The MFT results indicate the presence of the film forming second stage polymer at the surface of the latex particle and provides further evidence for a polystyrene rich core and polyacrylate rich shell for the two-stage latexes. 

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