Biomedical Engineering Reference
In-Depth Information
Table 10.1 Examples of active groups or molecules for organic-inorganic
hybridization.
Active groups
Molecule
Glycidoxy (epoxy)
Glycidoxypropyl trimethoxysilane (GPTMS)
Methacryl
Methacryloxypropyl trimethoxysilane,
CH 2 =
C(CH 3 )COCO(CH 2 ) 3 -Si(OCH 3 ) 3 -Si(OCH 3 ) 3
(
γ
-MPS)
(iso)Cyano
3-Isocyanatotriethoxysilane,
O = C = N-(CH 2 ) 3 -Si(OC 2 H 5 ) 3
Vinyl trimethoxysilane, CH 2 = CH-Si(OCH 3 ) 3 (VTMS)
Vinyl
Allyl trimethoxysilane, CH 2 = CHCH 2 -Si(OCH 3 ) 3
Allyl
Amino
Aminotripropyl triethoxysilane,
NH 2 (CH 2 ) 3 -Si(OCH 3 ) 3 (APTS)
-SH
Mercaptopropyl trimethoxysilane,
HS(CH 2 ) 3 -Si(OCH 3 ) 3 (MPTMS)
Mercaptopropyl triethoxysilane,
HS(CH 2 ) 3 -Si(OC 2 H 5 ) 3 (MPTES)
PDMS itself can be considered a hybrid. PDMS is synthesized by con-
densation between organic silanes that have typical formula R 4- n -SiX n
(X can be a halogen or another functional group that gives HO-Si
and R is an organic group) and the species HO-M in Equation 10.1.
One of the products of high-molecular-weight PDMS is silicone rubber.
Vapor-phase condensation proceeds with the halo-silanes even under
ambient conditions, since the Si-X group is very reactive. Its reactivity
is illustrated by fumes evolving when SiCl 4 is in contact with the air: it
is hydrolyzed with the humidity in the atmosphere to form nanometer-
sized SiO 2 particles (fume) with HCl as the by-product. TiCl 4 gives TiO 2
in a similar way. This means that Si-X groups are readily hydrolyzed to
yield Si-OH, and the halo-silane is susceptible to indirect condensation
with the HO-M under aqueous conditions. Direct condensation also
takes place between two alkoxysilanes (R 4- n Si(-OR ) n ):
Si-OR +
R O-Si
R -O-R
>
< >
Si-O-Si
< +
(10.3)
This condensation requires higher temperature or an active catalyst.
R 2 Si(OR) 2 is a candidate to be involved in the hydrolysis and conden-
sation. (CH 3 ) 2 Si(OH) 2 is a hydrolysis product of (CH 3 ) 2 SiCl 2 , whose
polycondensation leads to poly(dimethylsiloxane), [-Si(CH 3 ) 2 -O-].
 
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