336
polymerization methods) are low molecular weight (MW) cyclic and linear
oligomers.
PMHS homopolymers of random structures are prepared by the hydrolytic polycondensation of MDS, while cohydrolysis of MDS and DDS leads to copolysiloxanecontaining units: MeHSiO (D
H
) and Me 2 SiO (D). An addition of the monofunctional
TMCS (as an end capping agent) introduces end trimethylsiloxane (Me 3 SiO 0.5 )
groups and limits MWs of PMHS.
D
H n (n = 4–8) are also products of the hydrolytic polycondensation of MDS (Noll
1968; Hardman and Torkelson 1989; Crivello and Malik 1997; Tsuchida et al. 1997;
Zhang et al. 1998; Zhang et al. 2000; Rościszewski and Zielecka 2002;
Constantopoulos et al. 2004) or products of vacuum pyrolysis (at 400–450 °C) of
their hydrolizates (Lee 1966; Rościszewski et al. 1975; Finkelman 1987). Cyclic
dimethylsiloxane-co-PMHS (D m D
H n ) have been prepared by heterocondensation of
dimethylsilanediol or oligodimethylsiloxane-α,ω-diols with MDS (Reikhsfeld and
Ivanova 1962; Graczyk and Lasocki 1978, 1979a) or by pyrolysis of linear PDMSco- PMHS in the presence of trifluoromethanesulfonic acid (CF 3 SO 3 H, TFA)
(Chang and Buese 1993). The low MW oligo(methylhydro-co-diphenyl)siloxane
resins are synthesized by a non-hydrolytic sol-gel heterocondensation of methyldiethoxysilane (MeHSi(OEt) 2 , MDES) with diphenylsilanediol (Ph 2 Si(OH) 2 ),
which can be catalyzed by cationic exchange resins at 100 °C (Kim et al. 2012).
A very good control of MWs of PMHS has been achieved in the cationic polymerization of cyclosiloxanes: D
H n (n = 4–6) or D m D
H n or via copolymerization of D
H n
with dimethylcyclosiloxanes (D n , n = 3–5) (Scheme 14.1) (Reikhsfeld and Ivanova
1962; Graczyk and Lasocki 1978; Richards et al. 1993), usually with the addition of
M 2 (Wilcock and Hurt 1951; Gallagher 1966; Weiss 1993).
The copolymerization of D
H n with D n and M 2 occurs in the presence of different acid catalysts: cationic exchange resins, Lewis acids, protonic acids,
(Husemann and Greber 1962; Reikhsfeld and Ivanova 1962; Graczyk and Lasocki
Table 14.1 Boiling points and
29 Si-nuclear magnetic resonance (NMR) data of (α,ω-dichloro)
oligo(methylhydro)siloxanes
Siloxane
B.p.
[°C/mm Hg]
29 Si-NMR (in C 6 D 6 ) [δ, ppm]
ClMeHSiOSiHMeCl
103/748
−9.95, −9.98; -OSiMe(H)Cl
ClMeHSiOSiHMeOSiHMeCl
85–86/100 −12.08; -OSiMe(H)Cl −30.67;
-OSiMe(H)OClMeHSiO(SiHMeO) 2 SiHMeCl
70–71/12
−12.45; -OSiMe(H)Cl −32.23;
-OSiMe(H)OClMeHSiOSiHMeOSiHMeOSiHMeOSiHMeCl 97–98/15
−12.53; -OSiMe(H)Cl −32.48;
-OSiMe(H)O- −33.78;
-OSiMe(H)OClMeHSiOSiHMeO(SiHMeO) 2 SiHMeOSiHM
eCl
119/5
−12.56; -OSiMe(H)Cl −32.52;
-OSiMe(H)O- −34.02;
-OSiMe(H)OSource: Chruściel et al. (1997)
J. J. Chruściel
polymerization methods) are low molecular weight (MW) cyclic and linear
oligomers.
PMHS homopolymers of random structures are prepared by the hydrolytic polycondensation of MDS, while cohydrolysis of MDS and DDS leads to copolysiloxanecontaining units: MeHSiO (D
H
) and Me 2 SiO (D). An addition of the monofunctional
TMCS (as an end capping agent) introduces end trimethylsiloxane (Me 3 SiO 0.5 )
groups and limits MWs of PMHS.
D
H n (n = 4–8) are also products of the hydrolytic polycondensation of MDS (Noll
1968; Hardman and Torkelson 1989; Crivello and Malik 1997; Tsuchida et al. 1997;
Zhang et al. 1998; Zhang et al. 2000; Rościszewski and Zielecka 2002;
Constantopoulos et al. 2004) or products of vacuum pyrolysis (at 400–450 °C) of
their hydrolizates (Lee 1966; Rościszewski et al. 1975; Finkelman 1987). Cyclic
dimethylsiloxane-co-PMHS (D m D
H n ) have been prepared by heterocondensation of
dimethylsilanediol or oligodimethylsiloxane-α,ω-diols with MDS (Reikhsfeld and
Ivanova 1962; Graczyk and Lasocki 1978, 1979a) or by pyrolysis of linear PDMSco- PMHS in the presence of trifluoromethanesulfonic acid (CF 3 SO 3 H, TFA)
(Chang and Buese 1993). The low MW oligo(methylhydro-co-diphenyl)siloxane
resins are synthesized by a non-hydrolytic sol-gel heterocondensation of methyldiethoxysilane (MeHSi(OEt) 2 , MDES) with diphenylsilanediol (Ph 2 Si(OH) 2 ),
which can be catalyzed by cationic exchange resins at 100 °C (Kim et al. 2012).
A very good control of MWs of PMHS has been achieved in the cationic polymerization of cyclosiloxanes: D
H n (n = 4–6) or D m D
H n or via copolymerization of D
H n
with dimethylcyclosiloxanes (D n , n = 3–5) (Scheme 14.1) (Reikhsfeld and Ivanova
1962; Graczyk and Lasocki 1978; Richards et al. 1993), usually with the addition of
M 2 (Wilcock and Hurt 1951; Gallagher 1966; Weiss 1993).
The copolymerization of D
H n with D n and M 2 occurs in the presence of different acid catalysts: cationic exchange resins, Lewis acids, protonic acids,
(Husemann and Greber 1962; Reikhsfeld and Ivanova 1962; Graczyk and Lasocki
Table 14.1 Boiling points and
29 Si-nuclear magnetic resonance (NMR) data of (α,ω-dichloro)
oligo(methylhydro)siloxanes
Siloxane
B.p.
[°C/mm Hg]
29 Si-NMR (in C 6 D 6 ) [δ, ppm]
ClMeHSiOSiHMeCl
103/748
−9.95, −9.98; -OSiMe(H)Cl
ClMeHSiOSiHMeOSiHMeCl
85–86/100 −12.08; -OSiMe(H)Cl −30.67;
-OSiMe(H)OClMeHSiO(SiHMeO) 2 SiHMeCl
70–71/12
−12.45; -OSiMe(H)Cl −32.23;
-OSiMe(H)OClMeHSiOSiHMeOSiHMeOSiHMeOSiHMeCl 97–98/15
−12.53; -OSiMe(H)Cl −32.48;
-OSiMe(H)O- −33.78;
-OSiMe(H)OClMeHSiOSiHMeO(SiHMeO) 2 SiHMeOSiHM
eCl
119/5
−12.56; -OSiMe(H)Cl −32.52;
-OSiMe(H)O- −34.02;
-OSiMe(H)OSource: Chruściel et al. (1997)
J. J. Chruściel