UNPERTURBED CONFORMATION OF ISOTACTIC AND ATACTIC POLY(PENTENE-1) AT VARIOUS TEMPERATURES

The unperturbed molecular dimensions of atactic and isotactic polypentene-1 were determined by viscosity measurements in θ solvents, in the range 32° to 149°. It can be concluded that: 1. (a) around room temperature, the isotactic chains are more extended than the atactic chains; the volume pervaded by an isotactic molecule under unperturbed conditions is ≈20 per cent larger than that by an atactic chain of the same M; 2. (b) the unperturbed dimensions decrease with increasing temperature for both stereoisomers, but at different rates. It can be calculated: {A figure is presented}. The results are interpreted; the available data concerning d ln ro2/dT for atactic polypropylene and polybutene-1 are discussed. © 1969.