Chemistry Reference
In-Depth Information
Figure 10.5:
High-transparency polysiloxane elastomer used as a stress-relieving interlayer in the
type of safety glass or plastic used in windshields and canopies. The photograph was pro-
vided by the Dow Corning Corporation of Midland, MI.
“nonslumping” end-linkable paste had to be used rather than a liquid.
After the surface was coated, it was cured to give a remarkably faithful
reproduction that was easily removable from the original surface.
In the final example, a polysiloxane appears as an interlayer in the
types of plastic and glass laminates used for increased safety in wind-
shields and canopies in aircraft. The flexibility and thermal stability of
these polymers are great advantages in the case of high-performance air-
craft, which can experience wide variations in temperature. In this appli-
cation, a polysiloxane is chosen to give the highest transparency and good
adhesion to the plastic or glass outer layers. The excellent transparency of
such composites is readily seen in the samples displayed in figure 10.6.
Polysiloxanes are the materials of choice in the new “soft-lithography”
techniques.
21-25
Figure 10.7 briefly outlines the method. In the first step,
linear (liquid) polydimethylsiloxane (PDMS) is poured over the surface of
the master to be reproduced; it is then cross linked and peeled away from
the master surface. The PDMS surface containing the pattern is then
coated with a hydrophobic alkane thiol, and the pattern is transferred to
a gold surface (to which the thiol strongly binds). The pattern placed onto
the gold surface can then be developed using a variety of techniques, in-
cluding washing with a hydrophilic thiol to coat those parts of the sur-
face not covered by the hydrophobic thiol. The advantages of PDMS are (i)
high fluidity (which is required to make good replicas of the
