Bridge polymers

Fig. 4. (a) Polymer bridging between particles and (b), particle stabilization by adsorbed polymer (32). 

FIG. 10 SEM micrographs of (a) sUica nanoparticle/polymer [Si02/PDADMAC)3]-coated PS lat-ices and (b) hollow silica capsules. The hollow sUica capsules were obtained by calcining coated particles as shown in (a). The calcination process removes the PS core and the polymer bridging the silica nanoparticles, while at the same time fusing the silica nanoparticles together. Some of the silica capsules were deliberately broken to demonstrate that they were hollow (b). (From Ref. 106.)... 

The polymerization applied produces spherical polymer particles (1-10 pm diameter) connected by polymer bridges [3]. Thus, a one-piece polymer phase is obtained. The interstices between the particles have a characteristic length of a few micrometers. Overall, the polymer structure can be ascribed as lose. 

Adsorption on Kaolinite. As for polyacrylamides, adsorption of XCPS on kaolinite is conducted as a function of S/L and the results extrapolated to S/L=0. However, the S/L dependence of XCPS adsorption on kaolinite is considerably less than that for HPAM. This is due to the flat conformation of the adsorbed molecules of semirigid xanthan (25) compared to the more extended conformation of flexible HPAM (27). The absence of loops and tails in the adsorbed XCPS layer thus diminishes the probability of flocculation of particles by polymer bridging. The slight dependence in adsorption on S/L may therefore be attributed to coagulation of particles induced by Ca. ... 

The problems associated with the application of this (or any other) model have been discussed. Because of the form of the typical isotherm, which exhibits a broad plateau region, fitting of experimental results to the model requires that data be obtained over a very broad range of concentrations. This is often very difficult to accomplish in practice, especially when difference methods are used to determine the amount of polymer adsorbed. Evaluation of adsorption in real systems is further complicated by a lack of knowledge of the available solid surface area. The latter may be affected by particle size, shape and surface topography and by polymer bridging between particles. 

The increase in the rheological parameters, ri0> G0 and 1(5 with reduction in surface coverage points towards an increase in particle interaction. This could be the result of either flocculation by polymer "bridging" (which is favourable at coverages <0.5) or as a result of coagulation due to the van der Waals attraction between the "bare" patches on the particles. In the absence of any quantitative relationship between interaction forces and rheology, it is clearly difficult... 

B. Jiang, S.-W. Yang, R. Niver, and W.E. Jones, Jr., Metalloporphyrin polymers bridged with conjugated cyano-substituted stilbene units, Synth. Met., 94 205-210, 1998. 

This type of mechanism is likely to be partly operative in systems containing inorganic electrolytes as, for example, in the case of aluminium species. Some polyelectrolytes may also induce flocculation by charge neutralisation but the adsorbed polymer may also be able to bridge from one particle surface to another ( polymer bridging ). 

Figure 7.7 Diagramatic representation of flocculation by polymer bridging.

L. Cohen-Tannoudji, E. Bertrand, L. Bressy, C. Goubault, J. Baudry, J. Klein, J.-E. Joanny, and J. Bibette Polymer Bridging Probed by Magnetic Colloids. Phys. Rev. Lett. 94, 038301 (2005). 

C. Goubault, E. Leal-Calderon, J.-L. Viovy, and J. Bibette Self-Assembled Magnetic Nanowires Made Irreversible by Polymer Bridging. Langmuir 21, 3725 (2005). 

Polymer bridging has important consequences in the material and life sciences, including an influence on adhesion, tribology and polymer flow, micrombule formation and function, and cell surface interactions (de Gennes 1979 Fleer et al. 1993). Bridges occur when a polymer chain is either physisorbed or covalently bound to... 

Galactomannans have been used as flocculents (for the purification of ores, for example) and a study has been made of the gum structure by electron microscopy. The smallest fiber-diameter for an evaporated film of guar gum was found260 to be 4 nm, but, when a kaolinite-guar gum flocculate was examined, the diameter of the smallest fiber that was attached to the kaolin was found to be 10 nm. It is suggested that flocculation is caused by polymer bridging of the clay particles. 

Separan acrylamide polymer bridging chemical processing 2-10 0.2—10 ppm 1.00- 2.00 Dow Chemical Co. 

The A values of polymer metal complexes with different polymer bridges (16a d), having redox couples Mt/M2, where Mt/M2 is Fe2+/3+ or Cu+/2+, at both terminals of the bridge, were estimated based on quantum mechanical treatment (Fig. 6), It was concluded that not only system (16a) but also system 16c may be adiabatic over... 

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