Chloromethylation of polyphenylsiloxane prepolymers by silylation

Silylation of nonequilibrated phenyl‐T‐siloxane polycondensates by dimethylchloromethylchlorosilane involves only a small part of the silanol groups present in these prepolymers. At room temperature, silylation and condensation of the silanol groups occur at the same time. This condensation can be either intermolecular only or both intermolecular and intramolecular, depending on the initial condensation state of the prepolymer. It seems that no condensation reactions take place when the reaction is carried out with reflux. In any case, and even with strongly reactive disilazanes, no more than 35% of the silanol groups are consumed. The results give some information about a polymer, the structure of which is (after all) rather badly known.