Reactivity of cyclosiloxane with 3,3,4,4,5,5,6,6,6‐nonafluorohexyl group and its application to fluorosilicone synthesis

The reactivity of cyclosiloxane with 3,3,4,4,5,5,6,6,6‐nonafluorohexyl group and its application to fluorosilicone synthesis were studied. In contrast to the polymerization of the commercially available 1,3,5‐tris(3,3,3‐trifluoropropyl)‐1,3,5‐trimethylcyclotrisiloxane (CF 3 –D3), the polymerization of 1,3,5‐tris(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)‐1,3,5‐trimethylcyclotrisiloxane (C 4 F 9 –D3) with sodium hydroxide yielded 1,3,5,7‐tetrakis(3,3,4,4,5,5,6,6,6‐nonafluorohexyl)‐1,3,5,7‐tetramethylcyclotetrasiloxane {[C 4 F 9 CH 2 CH 2 (CH 3 )SiO] 4 (C 4 F 9 –D4)} as the major product, which was the result of the depolymerization by a backbiting mechanism. On the other hand, the polymerization of C 4 F 9 –D3 with trifluoromethanesulfonic acid yielded a polymer with good reproducibility, although the distribution of molecular weight tended to be bimodal. C 4 F 9 –D3 was also successfully copolymerized with octamethylcyclotetrasiloxane (D4). The properties of the obtained copolymers changed almost linearly with the amount of [C 4 F 9 C 2 H 4 (CH 3 )SiO] units, except for the surface tension. The surface tension of the copolymer containing more than 50% [C 4 F 9 C 2 H 4 (CH 3 )SiO] units by weight was almost as low as that of the homopolymer. When the copolymer containing 50% [C 4 F 9 C 2 H 4 (CH 3 )SiO] units by weight was examined for an antifoaming agent, it worked as effectively as the homopolymer in the toluene foaming system. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3333–3340, 2001