prosthesis or device. Similarly, a biomaterial used in an in vivo or ex vivo application

should minimize unwanted biological interactions.


 Silicones

 Silicones are widely popular materials and have many commercial uses today.

They are unique in many of the polymers used in biomedical devices in that they possess

a silicone-oxygen backbone instead of a carbon backbone. Their chemical and physical

properties allow for their use in a variety of applications. The simplest silicones are

polydimethylsiloxanes, a linear organosilicon compound whose structure can be seen in

Figure 2.4.

 CH3 CH3 CH3

 H3C- Si- 0 Si- O Si- CH3

 CH3 CH3 CH3

 Figure 2.4 Polydimethylsiloxane, trimethylsiloxy terminated



 PDMS oils, when not cross-linked, are used in fields such as cosmetics, food-

processing, and pharmaceutical preparations. Their lubricity and low surface tension

make them excellent additives for anti-foaming.[106]

 The methyl groups in the backbone and end caps of the PDMS molecule can be

replaced by both functional and non-functional molecules, including hydrogen, phenyl,

and vinyl groups. The significance of these substitutions is in their changes to the

chemical and physical property of the polymer, as well as the curing and processing

capabilities. Cross-linked PDMS forms a silicone elastomer that has excellent elongation

properties (20-700%) and moderate breaking strengths (- 1000 psi). They have been