Conformation of polyphenylsilsesquioxane molecules

Silesquiozanes. 2. Polysilsesquioxanes

“…The studies by Brown and co-workers [2] and Andrianov and coworkers (55] already showed that the experimental points relating to the dependence log [η = f log [M] are located on two curves with different values of the coefficient K and the exponent α. Confirmation of this fact has been provided by more recent studies carried out by the authors of publication [63], who established in the case of dilute solutions of polyphenylsesquioxanes that in the Mark-Houwink equation [η] = K • M a there is a change that occurs in the exponent α in the region 0.58 -1. 85.…”

“…The higher values of a indicate considerable rigidity of the polymer molecules. These authors discovered the presence of molecules with a statistical dimension of the Kuhn segment amounting to 50 Å and 250 Å, whereas Andrianov and co-workers [55] evaluated this value at 100 -200 Å. Tverdokhlebova and co-workers [63] established the possibility that the following regular cyclolinear macromolecular conformations can occur: cis-syndiotactic, cis-isotactic, cis-anti-cis-tactic and mixed. The calculated theoretical size of the Kuhn segment of a cis-syndiotactic molecule of polyphenylsilsesquioxane is about 1000 Å, whereas macromolecules with a Kuhn segment of about 50 Å have a conformation close to the cis-anti-cis-tactic.…”