Colloids chains attached

The first case concerns particles with polymer chains attached to their surfaces. This can be done using chemically (end-)grafted chains, as is often done in the study of model colloids. Alternatively, a block copolymer can be used, of which one of the blocks (the anchor group) adsorbs strongly to the particles. The polymer chains may vary from short alkane chains to high molecular weight polymers (see also section C2.6.2). The interactions between such... 

The morphology obtained by crystallizing an undiluted polymer can be considerably more complicated. The simplest model proposed consists of a system in which small crystallites exist, with amorphous chains attached to them like fringes on a colloidal aggregate. Such a system is called a micelle. This model is probably too simple except for a few polymers which form relatively few, very small crystallites. 

Multiarm star polymers have recently emerged as ideal model polymer-colloids, with properties interpolating between those of polymers and hard spheres [62-64]. They are representatives of a large class of soft colloids encompassing grafted particles and block copolymer micelles. Star polymers consist of f polymer chains attached to a solid core, which plays the role of a topological constraint (Fig. Ic). When fire functionality f is large, stars are virtually spherical objects, and for f = oo the hard sphere limit is recovered. A considerable literature describes the synthesis, structure, and dynamics of star polymers both in melt and in solution (for a review see [2]). 

The loss of entropy of a single polymer chain attached to a colloidal particle, assumed to be a plate, on compression is found from the Boltzmann relationship to be... 

Manipulation of single polymer chains has become a major direction of research in polymer science because such experiments can yield valuable insight into the relationship between the chemical structure and physical properties of macromolecules [1-3]. Such experiments do also depend on the conditions of the environment of the polymers, e.g., in an experiment where colloidal beads attached to the chain ends of a biopolymer are moved away from each other with laser tweezers. Then, the extension X) versus force (/) relation will depend on the quality of the solvent in which the polymer has been dissolved. Also, the structure of a polymer adsorbed on a substrate from solution will depend on the solvent quality [4, 5]. 

Chains attached to colloidal surfaces provide powerful forces for stabilization. Colloidal particles that normally coagulate from a solvent dispersion can thus be stabilized by adding a small amount of polymer to the dispersion. Such polymer additives are sometimes known as protective colloids, leading to steric stabilization. Both synthetic polymers and biopolymers such as proteins and gelatin are commonly used in both nonpolar and polar solvents. Industrially they are used in paints, toners, emulsions, suspensions, cosmetics, pharmaceuticals, processed foods, and lubricants. 

Several experiments of interest can be carried out with the SFA. One pos-sibihty is to have the chains attached at their ends to both surfaces, thus providing an attractive bridging effect (69,70). Bridging effects are extremely important in flocculation of colloidal dispersions, the opposite of stabilization. Clariflcation of wastewater provides an important application. 

An example of the conformation of long polyelectrolyte chains attached to colloidal latex particles is also shown here by cryo-TEM [590]. The dense grafting of the polyelectrolyte chains ( spherical polyelectrolyte brush, or SPB) leads to a confinement of the counterions... 

One can have the same type of situation in a blend of two mutually immiscible polymers (e.g., polymethylbutene [PMB], polyethylbutene [PEB]). When mixed, such homopolymers form coarse blends that are nonequilibrium structures (i.e., only kinetically stable, although the time scale for phase separation is extremely large). If we add the corresponding (PEB-PMB) diblock copolymer (i.e., a polymer that has a chain of PEB attached to a chain of PMB) to the mixture, we can produce a rich variety of microstructures of colloidal dimensions. Theoretical predictions show that cylindrical, lamellar, and bicontinuous microstructures can be achieved by manipulating the molecular architecture of block copolymer additives. 

Colloidal dispersions can be stabilized by attaching polymer chains to their surface [1-9]. When neutral polymer chains grafted on two parallel plates interpenetrate, a steric repulsion is generated. If the polymer chains grafted to the plates are charged, the double layer interaction between the two plates is also affected by the presence of the chains. 

Polyelectrolyte brushes are macromolecular monolayers where the chains are attached by one end on the surface and, at the same time, the chains carry a considerable amount of charged groups. Such poly electrolyte structures have received thorough theoretical treatment, and experimental interest has been vast due to the potential of brushes for stabilising colloidal particle dispersions or for... 

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