Diphenylsiloxane oligomers functionalized at both terminals and methods for the preparation thereof

A method for the preparation of a diphenylsiloxane oligomer having the following general formula

• G-(OSiPh.sub.2).sub.m O-G (i)
• wherein Ph denotes a phenyl radical, m is 3 to 50 and G has a formula independently selected from the group consisting of ##STR8## in which R, R.sup.4 and R.sup.5 are independently selected from the group consisting of methyl, phenyl and R.sup.1, R.sup.1 is selected from the group consisting of hydrogen and a monovalent hydrocarbon group having 2 to 8 carbon atoms excluding phenyl, tolyl, xylyl, and ethylphenyl radicals, Q is a divalent hydrocarbon group and k is independently 0 to 3 at each terminus of said oligomer with the proviso that k is >0 at one terminus of said oligomer, at least one substituent among R, R.sup.4 and R.sup.5 in formula (ii) is R.sup.1 and, when both R.sup.4 and R.sup.5 groups at one terminus of said oligomer are phenyl, groups R.sup.4 and R.sup.5 at the other terminus can not both be phenyl, said method comprising:
• (I) polymerizing hexaphenylcyclotrisiloxane using a lithium silanolate initiator of the formula
• G-O.sup.- Li.sup.+ (iv);
• and
• (II) reacting the product of step (I) with a silicon compound having the formula
• G-X (v)
• wherein G has its formula independently selected from said formula (ii) or said formula (iii) and X is selected from acyloxy, chlorine, bromine or iodine.

A method for the preparation of a diphenylsiloxane oligomer having the following general formula

• G-(OSiPh.sub.2).sub.m O-G (i)
• wherein Ph denotes a phenyl radical, m is 3 to 50 and G has a formula independently selected from the group consisting of ##STR9## in which R, R.sup.4 and R.sup.5 are independently selected from the group consisting of methyl, phenyl and R.sup.1, R.sup.1 is selected from the group consisting of hydrogen and a monovalent hydrocarbon group having 2 to 8 carbon atoms excluding phenyl, tolyl, xylyl, and ethylphenyl radicals, Q is a divalent hydrocarbon group and k is independently 0 to 3 at each terminus of said oligomer with the proviso that k is >0 at one terminus of said oligomer, at least one substituent among R, R.sup.4 and R.sup.5 in formula (ii) is R.sup.1 and, when both R.sup.4 and R.sup.5 groups at one terminus of said oligomer are phenyl, groups R.sup.4 and R.sup.5 at the other terminus can not both be phenyl, said method comprising:
• (I) polymerizing hexaphenylcyclotrisiloxane using a lithium silanolate initiator of the formula
• G-O.sup.- Li.sup.+ (iv);
• (II) reacting the product from step (I) with a cyclic siloxane trimer of the formula
• (R.sub.4 R.sub.5 SiO).sub.3 (vi)
• wherein R.sup.4 and R.sup.5 are defined as above;
• and (III) reacting the product from step (II) with a silane having a formula selected from
• R.sub.3 SiX (vii)
• or ##STR10## wherein R and Q are defined as above and X is selected from acyloxy, chlorine, bromine or iodine.