Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 4, pp. 619−621.
Pleiades Publishing, Ltd., 2013.
Original Russian Text © Yu.V. Khoroshavina, G.A. Nikolaev, S.K. Kurlyand, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 4, pp. 663−665.
Polymethyl(hexaﬂ uoroalkyl)siloxane Rubbers: Preparation
and Thermal Properties
Yu. V. Khoroshavina, G. A. Nikolaev, and S. K. Kurlyand
Lebedev Research Institute of Synthetic Rubber, St. Petersburg, Russia
Received April 25, 2011
Abstract—Polymethyl(hexaﬂ uoroalkyl)siloxane rubbers were synthesized by anionic and cationic polymerization
of 1,3,5-trimethyl-1,3,5-tris(hexaﬂ uoroalkyl)cyclotrisiloxanes and 1,1,3,3,5-pentamethyl-5-(triﬂ uoromethyltri-
ﬂ uorobicyclo[2.2.1]heptyl)cyclotrisiloxane. The thermal properties of the new ﬂ uorosiloxane polymers were
studied by thermal gravimetric analysis and differential scanning calorimetry.
Fluorosiloxane rubbers form the base of sealants
and vulcanized rubbers operating in a wide temperature
interval and exhibiting high resistance to oils, fuels,
lubricants, and aliphatic, aromatic, and chlorinated
hydrocarbons. New polymethyl(hexaﬂ uoroalkyl)
siloxane rubbers [1–3] are intended to replace
polymethyl(3,3,3-triﬂ uoropropyl)siloxane rubbers,
which are not commercially produced in Russia.
In this study, by anionic and cationic polymerization
of previously synthesized  1,3,5-trimethyl-1,3,5-
ethylcyclotrisiloxane (I) (R
, where R
triﬂ uorobicyclo[2.2.1]heptyl)cyclotrisiloxane (II)
, and 1,1,3,3,5-pentamethyl-5-(5-
cyclotrisiloxane (III) [(R
We prepared polymethyl(hexaﬂ uoroalkyl)
siloxane polymers: polymethyl(triﬂ uoromethyltri-
ﬂ uorocyclobutyl)ethylsiloxane (IV) HO(R
[2.2.1]heptyl)siloxane (V) HO[(R
H, and polymethyl(triﬂ uoromethyltriﬂ uorobicyc
lo[2.2.1]heptyl)siloxane (VI) HO(R
Cyclotrisiloxanes I and III were polymerized under
the action of perﬂ uoroalkanesulfonic acid CF
H (SA-41) at room temperature in a vacuum
(1 mm Hg). The polymer started to form immediately,
and after 3 h the viscosity ceased to change.
The maximal molecular weights of the polymers are
260 000–300 000. As in studies [5, 6] on polymerization
of octamethylcyclotetrasiloxane D
, it is seen that
the molecular weight of the polymer depends on the
catalyst concentration. Experiments showed that the
optimal concentration of SA-41 was 0.05 mol % of
the cyclotrisiloxane amount. The catalyst purity is
a signiﬁ cant factor: In polymerization of I with the
freshly distilled sulfonic acid, we obtained the polymer
of molecular weight 260 000 in 3 h, whereas with the
sulfonic acid that had not been distilled before use the
molecular weight of the polymer reached 150 000 only
in 6 h.
As expected , cyclotrisiloxane II does
not polymerize under the conditions of cationic
polymerization (CP) because of the joint action of the
steric and –I effects of the ﬂ uorine atom in the substituent.