Polymethylmethacrylate spheres

C. Parkinson et al. (17) considered the effect of particle size distribution on viscosity. They studied suspensions of polymethylmethacrylate) spheres in Nujol with diameters of 0.1, 0.6, 1.0 and 4.0 microns with different volume fractions and with different particle size combinations to determine the influence of size-distribution on the viscosity. Each particle size gave a certain contribution to the final viscosity based on the volume fraction and the hydrodynamic coefficient obtained from the empirical equation for that particle size. The contributions were expressed in the same form as in Mooney s model, and the viscosity was calculated from the product of each term, n... 

Phan, et al. (50) and Meeker, et al. (51) report low-shear viscosities of polymethylmethacrylate spheres in decalin and decalin tetraUn, the latter being an index-matching fluid. Their measurements of y(< ), which were confined to ( < , appear as Figure 10.4. Distinct stretched-exponential and power-law regimes are clearly visible, the transition concentration being found near 0.41 < < 0.43 and... 

Figure 10.5 Low shear viscosity of (a) (O) 56 and (o) 94 and (b) (o) 153 and (O) 230 nm diameter silica spheres in cyclohexane, with rj from tables in van der Werff and de Kruif(52), (c) 78 nm radius silica spheres in cyclohexane, r]r as tabulated by de Kruif, et al. 53), and (d) polymethylmethacrylate spheres in decalin, based on findings of Poon, etal. 54). Lines represent Eqs. 10.9 and 10.10. In (a) and (b), solid and dashed lines refer to the smaller and larger spheres.

Figure 10.6 Viscosity of surface-coated 301 nm radius polymethylmethacrylate spheres, showing accurate fits in the solutionlike and meltlike regimes, based on measurements of Segre, etal. 16).

The other kind of systems largely studied, consists of polymethylmethacrylate (PMMA) or silica spherical particles, suspended in organic solvents [23,24]. In these solvents Q 0 and uy(r) 0. The particles are coated by a layer of polymer adsorbed on their surface. This layer of polymer, usually of the order of 10-50 A, provides an entropic bumper that keeps the particles far from the van der Waals minimum, and therefore, from aggregating. Thus, for practical purposes uw(r) can be ignored. In this case the systems are said to be sterically stabilized and they are properly considered as suspensions of colloidal particles with hard-sphere interaction [the pair potential is of the form given by Eq. (5)]. 

Brown and Rymden [100] used QELSS to study diflfusion of linear polystyrenes and silica spheres through polymethylmethacrylate-.toluene. Toluene and PMMA are almost exactly index-matched, so scattering arises from the dilute probe chains. The matrix molecular weight M spanned 110 kDa- 1.43 MDa. Probe polystyrenes had P of 2.95, 8, and 15 MDa, with M /M of 1.06, 1.08, and 1.30, respectively. Figure 21 shows Dp/Dpo... 

The crosslinked organic microbeads coated with shp agent may be prepared by various methods. The crosslinked organic microbeads may be prepared, for example, by a procedure in which monomer droplets containing an initiator may be sized and heated to give solid polymer spheres of the same size as the monomer droplets. The pol5mier is polymethylmethacrylate crosslinked with divinylben-... 

Figure 9.28 Probe diffusion coefficients for (a) 350 kDa polymethylmethacrylate in good solvents tetrahydrofuran (O) and N,N-dimethylformamide (0), and the Theta solvent dioxane water ( ), after Gold, et al.(45), and (b) 67 nm polystyrene spheres in aqueous 139 kDa HPC at (O) 10 °C (good solvent conditions) and ( ) 41 (pseudo-theta point), after Phillies and Clomenil(46).

PPy has been coated on polymethylmethacrylate (PMMA) or polyethylene spheres " using a chemical polymerization process. The spheres were dispersed in methanol and then added to water containing FeClj oxidant. Pyrrole dissolved in water was subsequently added. The coated spheres could be mixed with noncoated spheres of PMMA and hot-pressed to obtain films with conductivities of 3.5 S cm". ... 

Our findings for the weakly charged colloids suggest that even a slight softness of the intermolecular potential, has important consequences for the crystallization behavior. This effect could be relevant for experimental hard-sphere colloids, as these particles are, in fact, slightly soft. A particularly popular experimental hard-sphere colloid consists of a polymethylmethacrylate (PMMA) core coated with a thin layer of poly-12-hydroxystearic (PHSA). Due to the coating, the particles are slightly soft. We smdied the effect that such a softness has on the phase behavior and the crystallization kinetics [75]. 

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