Dilution with polymethylmethacrylate

The solution was diluted with cyclohexane, a solvent for polystyrene and a nonsolvent for polymethylmethacrylate, and the product thereafter precipitated by addition to methanol THF/cyclohexane/methanol = 1 2 10 (by volume). The product was finally dried to constant weight. 

Acrylates. Polymethylmethacrylate (Lucite, Plexiglas, Perspex) is easily machined and is widely used with dilute aqueous solutions. Acrylates are resistant to nonoxidizing acids and weak alkalies, but are attacked by concentrated oxidizing acids and strong alkalies. They will withstand petroleum oils and most alcohols, but are generally unsuitable for use in contact with organic solvents. They are dissolved by ketones, esters, and aromatic and chlorinated hydrocarbons. They are thermoplastic and cannot be used continuously above 75 °C. The acrylates are perfectly clear and transparent and often are used to make shields or inert atmosphere enclosures. The materials bum slowly when ignited. 

There are several ways of isolating molecules, in addition to dilution in appropriate solvents. For instance, extremely long PDA chains can be diluted in their monomer single crystal by exploiting the peculiar polymerization mechanism [91] of this class of polymers. In the case of CPs blended with non-conjugated macromolecules (polyethylene, polymethylmethacrylate, etc.) or inclusion crystalline compounds [92], the interaction between molecule and environment is usually strongly suppressed, but at the expense of the sample optical density, in a way that may easily challenge the common sensitivity of time-resolved techniques. 

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... 

Nemoto, et al. report sedimentation and tracer diffusion of dilute polymethylmethacrylate probes in dilute and nondilute polystyrene thiophenol(24,25). Polystyrene and thiophenol are isopycnic, permitting s of PMMA probes in polystyrene thiophenol to be determined unambiguously with ultracentrifugation. 

Reasonable confidence that these two curves are appropriate to describe the viscosity dependence is only possible because the number of independent measurements is very large. With fewer points Sasaki, et a/.(16) examined dilute polymethylmethacrylate in seven solvents, finding a x t]) qualitatively similar to... 

Konak, et al report dynanuc light scattering spectra of mixtures of polystyrene and polymethylmethacrylate in toluene(77). Neither polymer was dilute. Comparison was made for a limited number of concentrations with theoretical models arising from work of Benmouna, et al(6T). Treating spectra as bimodal, the ratio of relaxation times was predicted theoretically to better than 50%, but predictions of the mode amplitude ratio were often inexact by factors of 2 or 3. 

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