Abstract
AbstractOn a sample of poly(methyl methacrylate) prepared by an anionic polymerization technique with sodium biphenyl in tetrahydrofuran at –78°C, abnormal cloud‐point curves in nonpolar theta solvents, p‐xylene, and carbon tetrachloride were observed. The effect of solvent polarity on precipitation behavior of the sample solutions was examined. It is found that the more polar the solvent used, the more normal the cloud‐point curve becomes. Osmometry on the sample solutions in p‐xylene yielded much higher molecular weights than those obtained in a good solvent (toluene) and in a polar theta solvent (acetonitrile). The results obtained show that poly(methyl methacrylate) molecules prepared in this manner are liable to associate with each other in nonpolar media. This feature is considered to be responsible for the observed anomalies in the cloud‐point curves. This type of association is discussed and compared with the other two kinds of association phenomena reported in the literature.
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