347
in appropriate heptades were determined, but the microstructure of poly(H- siloxane)
end chains was not analyzed.
The microstructure of random PDMS-co-PMHS prepared by the hydrolytic
polycondensation of chlorosilanes, changed with decrease of the content of Si-H
groups and increase of their MWs. In the determinations of tacticities of PDMS-coPMHS, were also very helpful
29
Si-NMR spectra of the above listed ten model
H-siloxanes (Chruściel 1999a) and literature data published by Harris and
Kimber (1974).
The δ values of Si atoms in end groups (Me 3 SiO 0.5 ) changed in the tetrades, and
were influenced by the substituents at the Si atoms of the siloxane chains, which
interacted through six Si-O bonds. The δ values of silicon atoms of D units are sensitive to the effects of the substituents, which are transferred through four siloxane
bonds, which means that they undergo changes in pentades, and the δ values from
29
Si-NMR of middle Si atoms in units D
H
changed in triads (DD
H
D, DD
H
D
H
,
D
H
D
H
D
H
), since magnetic interactions of substituents are transferred through two
siloxane bonds (Table 14.2).
The microstructure of the statistical (random) branched PDMS-r-PMHS prepared by the hydrolytic polycondensation of appropriate chlorosilanes was also
determined by the
29
Si-NMR method (Chruściel et al. 2008, 2011a, 2011b). It was
even more complex, than it had been observed for linear random PMHS, due to the
presence of many random sequences, composed of units: D, D
H
, M, and also
sequences of these moieties having trifunctional branching points T (or/and T
H
). An
interpretation of the
29
Si-NMR spectra of PDMS-r-PMHS was based on analysis of
the microstructure of PDMS-b-PMHS (Chruściel et al. 1997, 1999) and on the literature data (Harris and Kimber 1974; Cancouët et al. 2000a, b).
The microstructure of the siloxane chains in branched PMHS containing mers
D
H
and D, branching units SiO 4/2 (Q), and end groups M (PMHS-Q) have also been
established by means of the
29
Si-NMR (Chruściel et al. 2018).
14.4 Synthesis of Branched Random
Poly(methylhydroborosiloxane)s (PMHBS)
Branched PMHBSs (br-PMHBS) of a random structure with a general formula:
B D D T M where k
m
n
x
p k
,
k m
H
n
x
p
’
, , , ;
;
,
, , ;
=
≥
≥
=
= +
(
)
3 6 9 12
1
10
0 3 6
2
were prepared by the hydrolytic copolycondensation method of the solution of a
‘precursor’ of tris(chlorodimethylsiloxy)borane (B(OSiMe 2 Cl) 3 ) and appropriate
organic chlorosilanes in diethyl ether, at a temperature from −8 °C to RT, in the
presence of C 5 H 5 N as a nucleophilic reaction catalyst and acceptor of HCl, according to the following reaction scheme (Chruściel et al. 2009, 2011c):
14 Hydrosilyl-Functional Polysiloxanes: Synthesis Reactions and Applications
in appropriate heptades were determined, but the microstructure of poly(H- siloxane)
end chains was not analyzed.
The microstructure of random PDMS-co-PMHS prepared by the hydrolytic
polycondensation of chlorosilanes, changed with decrease of the content of Si-H
groups and increase of their MWs. In the determinations of tacticities of PDMS-coPMHS, were also very helpful
29
Si-NMR spectra of the above listed ten model
H-siloxanes (Chruściel 1999a) and literature data published by Harris and
Kimber (1974).
The δ values of Si atoms in end groups (Me 3 SiO 0.5 ) changed in the tetrades, and
were influenced by the substituents at the Si atoms of the siloxane chains, which
interacted through six Si-O bonds. The δ values of silicon atoms of D units are sensitive to the effects of the substituents, which are transferred through four siloxane
bonds, which means that they undergo changes in pentades, and the δ values from
29
Si-NMR of middle Si atoms in units D
H
changed in triads (DD
H
D, DD
H
D
H
,
D
H
D
H
D
H
), since magnetic interactions of substituents are transferred through two
siloxane bonds (Table 14.2).
The microstructure of the statistical (random) branched PDMS-r-PMHS prepared by the hydrolytic polycondensation of appropriate chlorosilanes was also
determined by the
29
Si-NMR method (Chruściel et al. 2008, 2011a, 2011b). It was
even more complex, than it had been observed for linear random PMHS, due to the
presence of many random sequences, composed of units: D, D
H
, M, and also
sequences of these moieties having trifunctional branching points T (or/and T
H
). An
interpretation of the
29
Si-NMR spectra of PDMS-r-PMHS was based on analysis of
the microstructure of PDMS-b-PMHS (Chruściel et al. 1997, 1999) and on the literature data (Harris and Kimber 1974; Cancouët et al. 2000a, b).
The microstructure of the siloxane chains in branched PMHS containing mers
D
H
and D, branching units SiO 4/2 (Q), and end groups M (PMHS-Q) have also been
established by means of the
29
Si-NMR (Chruściel et al. 2018).
14.4 Synthesis of Branched Random
Poly(methylhydroborosiloxane)s (PMHBS)
Branched PMHBSs (br-PMHBS) of a random structure with a general formula:
B D D T M where k
m
n
x
p k
,
k m
H
n
x
p
’
, , , ;
;
,
, , ;
=
≥
≥
=
= +
(
)
3 6 9 12
1
10
0 3 6
2
were prepared by the hydrolytic copolycondensation method of the solution of a
‘precursor’ of tris(chlorodimethylsiloxy)borane (B(OSiMe 2 Cl) 3 ) and appropriate
organic chlorosilanes in diethyl ether, at a temperature from −8 °C to RT, in the
presence of C 5 H 5 N as a nucleophilic reaction catalyst and acceptor of HCl, according to the following reaction scheme (Chruściel et al. 2009, 2011c):
14 Hydrosilyl-Functional Polysiloxanes: Synthesis Reactions and Applications