Improved expression of the mean‐square radius of gyration, 3. 1,4‐polydienes

Abstract The mean‐square radii of gyration of cis‐ and trans‐1,4‐polybutadiene and corresponding 1,4‐polyisoprene were derived using Abe's and Flory's rotational isomeric scheme. Calculations performed using available experimental data showed that the dependence of the mean‐square radius of gyration on the molecular weight for these stereoregular polydienes can be expressed as where a and b are constants characteristic of the polymer. This behaviour is analogous to that of vinyl polymers and poly‐1,1‐disubstituted ethylenes discussed in the preceding papers of the present series. The mean‐square radius of gyration of 1,4‐polyisoprene with predominantly trans units is more sensitive to stereoirregularity than with predominantly cis units. However, 1,4‐polybutadiene chains are comparatively insensitive to the stereochemical composition.