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suppressing biofouling. 76, 142 The incorporation of diphenylsiloxane oils in
PDMS is also effective. Methods have been developed to minimize deple-
tion of these oils when the surfaces are exposed to freshwater and other
marine environments. 143
Coatings of the block copolymers, PDMS-polyurethane and PDMS-
acrylic-polyurethane, 144 and PDMS-polyurea, 145 are also effective antibio-
fouling agents as are tethered quarternary ammonium salts in a
cross-linked PDMS matrix. 65
6.9 MECHANICAL ASPECTS
6.9.1 Friction and Lubricity
Frictional effects of PDMS sliding on gold surfaces, 146 glass, 147 silicon oxide
surfaces, 148 or glassy polymers, 149, 150 have been investigated in detail.
There has also been some interest in self-lubricating biomaterials. 151, 152
6.9.2 Adhesion
Adhesion between polymers and various surfaces has long been of general
interest. 153, 154 PDMS samples of varying degrees of cross linking were
studied to determine the extent to which they adhered to one another
(self-adhesion). 155 This type of adhesion was further explored by prepar-
ing PDMS model networks having known numbers of dangling chains. 81
The adhesion hysteresis increased with increase in the number of dangling
chains because of the increase in the number of such chains bridging the
interface.
Similar studies have been carried out on the adhesion of PDMS to poly-
carbonate using thermal gradients and x-ray photoelectron spectros-
copy, 156 to mica using atomic force microscopy, 157 and to glass 158, 159 or to
silicon 160 using measurements of force, contact angle, or other properties.
There has also been considerable interest in the adhesion strength be-
tween coated particles and polymer matrixes. 161 Surface functionalization
has been used to improve adhesion. 162, 163
Modeling has been used to clarify the dependence of adhesive failure in
PDMS on its viscosity, the adhesive thickness, the substrate properties,
some rheological aspects, and peeling velocities. 164
Interfacial tension between PDMS and another polymer such as liquid
polybutadiene has also been studied. 165 The surface behavior of PDMS-
filled nanoporous anodic alumina has been reported. 166
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