Typical glassy polymers such as polystyrene at room temperature have E values

around 3 GPa, while soft rubbers are closer to 2 MPa.1120] PDMS based elastomers have

a somewhat wide range of moduli, from 0.1 MPa to 10 MPa.111ll The change is due to

the curing characteristics and the size of the oligomers, which affect the cross-link

density, molecular weight between cross-links, and physical entanglements.

 Currently, we are able to vary the modulus of our base Silastic T-2 elastomer over

a range of moduli from -0.1 MPa to -3 MPa with the addition of functionalized and

unfunctionalized PDMS oils. These oils can take the form of linear PDMS or larger

"bulky" oils with side chains. By varying the molecular weight and functionalization of

these additives, the variables mentioned above can be altered, without significantly

changing the surface chemistry of the samples. The majority of the development and

characterization of this system was performed by other members of the group, and so will

not be discussed in great detail in this thesis. However, since the materials with differing

moduli are of critical importance to the main purpose of this work, a description of the

specific oils and testing methods will be discussed in the characterization section.

 Research in our group has focused on the effect of mechanical properties on

biofilm formation, whether the film is in the form of algal spores or endothelial cells.

Kendall modeled adhesion behavior on elastomers by deriving formulae for the removal

of rigid solids off of elastomers with varying thickness.[122] The critical pull-off force, Pc,

required to remove a rigid cylinder with a radius of a from a film of thickness t is given

by


 2waK
 p.=^[t