340
in the presence of triethylamine (Et 3 N) and 4-(N,N-dimethylamino)pyridine
(DMAP) (10:1). Low MW volatile products were removed under vacuum at a temperature of 125–150 °C. Branched PMHS-Q with dynamic viscosities of 8–30 cP
were prepared with 57–84 wt.% yields (Chruściel et al. 2018).
Recently, Si-H functionalized liquid hyperbranched resins, terminated with
Me 3 SiO groups were synthesized by the partial hydrolytic polycondensation of
alcoholic solutions of alkoxysilanes: trimethoxysilane (HSi(OMe) 3 ), M 2 and phenyltrimethoxysilane (PhSi(OMe) 3 ), at pH = 3. Similarly, highly branched silicone
resins with HSiO 1.5 (T
H
) and other siloxane units (with excellent dielectric properties and thermal resistance) were obtained by the hydrolytic copolycondensation of
HSi(OMe) 3 and RSi(OMe) 3 (R = Ph or Me) or/and Ph 2 Si(OMe) 2 in the presence of
M 2 , followed by an equilibration with HCl, at 5–60 °C, thus exhibiting excellent
dielectric properties and thermal resistance (Liang et al. 2009; Zhang et al. 2011;
2012a, b).
14.2.4 Synthesis of PHS and PMHS With Cage Structures
Silsesquioxanes have the general formula (RSiO 1.5 ) n , where R is a hydrogen atom or
other organic and functional group. The most important silsesquioxanes are
((HMe 2 SiO)SiO 1.5 ) 8 and T
H 8 . Crystalline spherical (‘spherosiloxanes’), ladder (cage)
poly(silsesquioxane)s (POSS), containing reactive Si-H groups in the corners of
their cubes: T
H 8 , T
H 10 , T
H 12 , T
H 14 and T
H 16 (Pielichowski et al. 2006; Cordes et al.
2010; 2011; Marciniec 2009; Markovic et al. 2011), were prepared more frequently
with low yields (~11–22%) by the hydrolytic polycondensation of trimethoxysilane
(HSi(OMe) 3 ) in the medium of concentrated H 2 SO 4 (Müller et al. 1959; Frye and
Collins 1970) or acetic acid saturated with anhydrous HCl (Husemann and Greber
1962; Frye and Collins 1970; Jap. Pat. 6,086,017, 1985; Agaskar et al. 1987;
Agaskar 1989; Hasegawa and Motojima 1992; Hasegawa 1994; Xie et al. 1996;
Zhang et al. 1998; 2000; Constantopoulos et al. 2004), or HSiCl 3 , in methanol
towards FeCl 3 (Agaskar 1990; Bassindale and Gentle 1993; Crivello and Malik 1997).
However, using 2:1 (H 2 O:HSiCl 3 ) mole ratio at 0 °C under argon atmosphere,
(T
H
) n was obtained with high yield (95%), while mixed silicates (T
H
) n (MeSiO 1.5 ) m
(m:n = 2.5, 5 and 10%) were prepared from HSiCl 3 and MeSiCl 3, under similar
conditions (Henderson et al. 2009). Hydrolytic condensation of TES, catalyzed by
HCl in mixed solvents, gave soluble multifunctional cage-like and network-like
PHSSQs (Su et al. 2007). Monosubstituted cage silsesquioxanes, R’R 7 Si 8 O 12
(R’ and R - organic substituents or H or Cl) were prepared by three different methods: cohydrolysis of trifunctional organo- or hydrosilanes, substitution reactions
occurring with retention of the siloxane cage, and corner cap reactions (Marcolli
and Calzaferri 1999).
T
H 8 is a white solid soluble in methyl isobutyl ketone (Hasegawa and Motojima
1992), which is commercially available as 10–18% solutions called as HSQ (Yang
and Chen 2002; Schmid et al. 2004; Chen et al. 2006; Choi et al. 2007; Hessel et al.
J. J. Chruściel
in the presence of triethylamine (Et 3 N) and 4-(N,N-dimethylamino)pyridine
(DMAP) (10:1). Low MW volatile products were removed under vacuum at a temperature of 125–150 °C. Branched PMHS-Q with dynamic viscosities of 8–30 cP
were prepared with 57–84 wt.% yields (Chruściel et al. 2018).
Recently, Si-H functionalized liquid hyperbranched resins, terminated with
Me 3 SiO groups were synthesized by the partial hydrolytic polycondensation of
alcoholic solutions of alkoxysilanes: trimethoxysilane (HSi(OMe) 3 ), M 2 and phenyltrimethoxysilane (PhSi(OMe) 3 ), at pH = 3. Similarly, highly branched silicone
resins with HSiO 1.5 (T
H
) and other siloxane units (with excellent dielectric properties and thermal resistance) were obtained by the hydrolytic copolycondensation of
HSi(OMe) 3 and RSi(OMe) 3 (R = Ph or Me) or/and Ph 2 Si(OMe) 2 in the presence of
M 2 , followed by an equilibration with HCl, at 5–60 °C, thus exhibiting excellent
dielectric properties and thermal resistance (Liang et al. 2009; Zhang et al. 2011;
2012a, b).
14.2.4 Synthesis of PHS and PMHS With Cage Structures
Silsesquioxanes have the general formula (RSiO 1.5 ) n , where R is a hydrogen atom or
other organic and functional group. The most important silsesquioxanes are
((HMe 2 SiO)SiO 1.5 ) 8 and T
H 8 . Crystalline spherical (‘spherosiloxanes’), ladder (cage)
poly(silsesquioxane)s (POSS), containing reactive Si-H groups in the corners of
their cubes: T
H 8 , T
H 10 , T
H 12 , T
H 14 and T
H 16 (Pielichowski et al. 2006; Cordes et al.
2010; 2011; Marciniec 2009; Markovic et al. 2011), were prepared more frequently
with low yields (~11–22%) by the hydrolytic polycondensation of trimethoxysilane
(HSi(OMe) 3 ) in the medium of concentrated H 2 SO 4 (Müller et al. 1959; Frye and
Collins 1970) or acetic acid saturated with anhydrous HCl (Husemann and Greber
1962; Frye and Collins 1970; Jap. Pat. 6,086,017, 1985; Agaskar et al. 1987;
Agaskar 1989; Hasegawa and Motojima 1992; Hasegawa 1994; Xie et al. 1996;
Zhang et al. 1998; 2000; Constantopoulos et al. 2004), or HSiCl 3 , in methanol
towards FeCl 3 (Agaskar 1990; Bassindale and Gentle 1993; Crivello and Malik 1997).
However, using 2:1 (H 2 O:HSiCl 3 ) mole ratio at 0 °C under argon atmosphere,
(T
H
) n was obtained with high yield (95%), while mixed silicates (T
H
) n (MeSiO 1.5 ) m
(m:n = 2.5, 5 and 10%) were prepared from HSiCl 3 and MeSiCl 3, under similar
conditions (Henderson et al. 2009). Hydrolytic condensation of TES, catalyzed by
HCl in mixed solvents, gave soluble multifunctional cage-like and network-like
PHSSQs (Su et al. 2007). Monosubstituted cage silsesquioxanes, R’R 7 Si 8 O 12
(R’ and R - organic substituents or H or Cl) were prepared by three different methods: cohydrolysis of trifunctional organo- or hydrosilanes, substitution reactions
occurring with retention of the siloxane cage, and corner cap reactions (Marcolli
and Calzaferri 1999).
T
H 8 is a white solid soluble in methyl isobutyl ketone (Hasegawa and Motojima
1992), which is commercially available as 10–18% solutions called as HSQ (Yang
and Chen 2002; Schmid et al. 2004; Chen et al. 2006; Choi et al. 2007; Hessel et al.
J. J. Chruściel