Abstract
By viscosity measurements in θ solvents at various temperatures, values of unperturbed dimensions and of (d ln r 0 2 / dT ) are calculated for isotactic and atactic polybutene-1. (d ln r 0 2 / dT ) values for the two stereoisomers are also calculated by measurements of [η] in a good solvent at various temperatures, according to the theories of Flory-Fox, Kurata-Stockmayer-Roig and Flory-Fisk; the reliability of these theories is estimated. The conclusions are: 1. (1) Both the atactic and isotactic polymer dimensions decrease with increase of temperature, over the range investigated; however, (d ln r 0 2 / dT ) for isotactic polymer is greater than for atactic. 2. (2) The variation of log K θ with T for atactic polybutene cannot be represented by a straight line over a wide range of temperature; it tends to increase in the lower temperature region. A similar behaviour appears for isotactic counterpart. 3. (3) At fairly low temperature (i.e. at room temperature or slightly higher), isotactic polybutene shows larger dimensions than atactic polymer of the same molecular weight. 4. (4) At fairly high temperature (near the melting point of the bulk isotactic polymer), the dimensions of the two stereoisomers are practically the same.
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