| abstract |
Halogen-substd. (un)branched polysiloxanes are obtd. by partial hydrolysis of halosilanes of formula RaSiX(4-a) (I), where a = 2 if 1 silane is used, or a =0-3 if a mixt. of silanes is used, R is H or an (un)satd., is not > 18C monovalent (ar)aliphatic or aromatic hydrocarbon residue, opt. substd. by halogen or CN, and X is Cl or Br, in presence of RFSO3H, (where RF is a perfluoro is not > 10C alkyl residue), as catalyst. The process is 1-stage, and gives high yields, with very small prodn. of low-mol. volatile cpds. The prod. has narrow mol. wt. distribution and reproducible properties. The siloxane chain does not contain atoms introduced by the catalyst. |