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Table 1.2. NOTATIONS FOR VARIOUS POLYSILOX ANE STRUCTUR AL UNITS
Notation
Structure
Examples
M
R 3 SiO 0.5
MM
Dimer (CH 3 ) 3 SiOSi(CH 3 ) 3
D
R 2 SiO
MD 6 M
Oligomer (CH 3 ) 3 Si[OSi(CH 3 ) 2 ] 6 OSi(CH 3 ) 3
D
R 2 SiO
D 3
Cyclic trimer [Si(CH 3 ) 2 O] 3
T
RSiO 1.5
TT
Two trifunctional cross links RSi(O 2 )OSi(O 2 )R
Q
SiO 2
Q
Silica
M 1
M 11
Si
M 2
Si
O
O
Si
O
Si
M 10
O
M 3
O
Si
Si
M 9
O
O
M 4
Si
Si
O
O
M 8
M 5
Si
O
O
Si
Si
M 7
M 6
Figure 1.1:
The polysiloxane chain backbone in the low-energy, planar, all- trans conformation. 75
Arrows represent group dipoles M for each Si-O-Si pair of consecutive skeletal bonds.
Because of the cancelation of dipoles, the dipole moment of oligomers depends on mo-
lecular weight.
“M,” the difunctional unit R 2 SiO “D,” the trifunctional unit RSiO1.5 “T,”
and the quadrifunctional SiO 2 “Q.” For example, the dimer (CH 3 ) 3 SiOSi(CH 3 ) 3
is termed “MM,” the oligomer (CH 3 ) 3 Si[OSi(CH 3 ) 2 ] 10 OSi(CH 3 ) 3 is termed
“MD 10 M,” and the cyclic trimer [Si(CH 3 ) 2 O] 3 is called “D 3 .” Table 1.2 sum-
marizes this nomenclature. Unprimed abbreviations are taken to mean the
R substituents are methyl groups, since these are the most common and the
most important. Primed abbreviations are used for other substituents, the
most important of which is probably the phenyl group.
 
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