Chemistry Reference
In-Depth Information
roles, some polymers were prepared to have PDMS side chains on a
poly(phenylacetylene) main chain.
34
Siloxane-terminated solubilizing
side chains are used to improve the properties of thin-film transistors.
35
Silalkylene polymers have methylene groups replacing the oxygen
atoms in the backbone. Poly(dimethylsilmethylene) is an example,
[Si(CH
3
)
2
-CH
2
]
x
.
36- 46
A variation on this theme is to include aryl groups,
for example, in poly(dimethyldiphenylsilylenemethylene) [Si(CH
3
)
2
-CH
2
-
Si(C
6
H
5
)
2
]
x
.
16,
28,
45,
47-55
Other aryl substituents, specifically tolyl groups,
have also been included as side chains.
56-57
It is also possible to insert a silphenylene group [Si(CH
3
)
2
-C
6
H
4
-] into
the backbone of the polysiloxane repeat unit to give [Si(CH
3
)
2
-C
6
H
4
-
Si(CH
3
)
2
O-], in which the phenylene can be
para
or
ortho
or
meta
.
58-61
A
specific example is poly(tetramethyl-
p
-silphenylene-siloxane).
13, 45, 48-49, 62-71
Similarly, it is possible to use anthrylene groups
51
or fluorene groups
72
in-
stead of phenylene groups.
Most fluorosiloxane polymers
73
have the fluorine atoms in alkyl side
chains
74
but preceded by methylene spacers in the side chain to prevent
the F atoms from destabilizing the chain backbone. The most important
example of this type is poly((3,3,3-trifluoropropyl)methylsiloxane),75-79
75-79
but other examples include low molecular weight model organosiloxanes
containing perfluoroether side chains.
80
Some fluorinated silsesquioxane
polymers have also been prepared and characterized with regard to their
surface tension.
81
Fluorine atoms have also been placed on polysiloxanes having aromatic
side chains (e.g., in poly(phenylmethylsiloxanes)). Examples are poly(4-fluo-
rophenylmethylsiloxane),
82-83
poly(3,5-difluorophenylmethylsiloxane),82
82
poly(3,5-bis(trifluoromethyl)phenylmethylsiloxane),82
82
poly(pentafluoroph-
enylmethylsiloxane),
84
and perfluorocyclobutane aromatic polyethers.
85
An-
other interesting example involved hexafluoroisopropanol-functionalized
polysiloxanes that are being offered as new coating materials for sensors.
86
In some cases, the fluorosiloxane groups were simply used to cap chains of
polybutadiene.
87
More complicated structures have been formed by bridging single poly-
siloxane chains with oxygen atoms to give ladder-like polymers, the most
common example being poly(phenylsilsesquioxane).
16, 52, 88-94
3.2 REACTIVE CHAINS
In the typical ring-opening polymerization, reactive hydroxyl groups are
automatically formed at the ends of the chains.
95-96
Substitution reactions
